2026-02-04T00:00:00+00:00 https://blog.npry.dev/atom.xml 2026-02-04T00:00:00+00:00 2026-02-04T00:00:00+00:00 Nathan Perry https://blog.npry.dev/1pass-codesign/ <p>I use <a href="https://librewolf.net">LibreWolf</a> as my daily driver web browser and <a href="https://1password.com">1Password</a> as my password manager. Notionally, 1Password supports integration between the browser extension and the desktop app via native messaging, but this traditionally didn't work for non-blessed browsers (Chrome, Firefox, Safari, eventually Brave and Arc).</p> <p>This is to protect against anything else on your computer pretending to <em>be</em> the browser and stealing all your credentials, since the pipe provided by the native messaging host is privileged and has complete access to whatever vaults are decrypted in the native app. The NMH checks both browser identity and code signature validity to ensure that its parent process really is the browser it says it is.</p> <p>Recently, Agilebits has opened up the ability for end users to add entries to their local browser whitelist -- they did this on Linux and macOS first, but the change was also recently rolled out to Windows, which is my lowest-potential-energy OS platform. I was excited to finally not have to sign into the browser extension every 10 minutes, but unfortunately, LibreWolf <a href="https://codeberg.org/librewolf/issues/issues/2664">doesn't yet provide code-signed executables</a>, though they're working with <a href="https://ossign.org">OSSign</a> to remedy this (who appear to be swamped with requests for certs). In the meantime, the 1Password browser integration doesn't work because the code signature check fails.</p> <p>I resolved this by creating a local self-signed cert, adding it as a root CA, and signing the executable myself. Evidently, 1Password doesn't embed its own CA trust bundle, because this works fine.</p> <p>In an admin PowerShell session:</p> <pre data-lang="powershell" class="language-powershell z-code"><code class="language-powershell" data-lang="powershell"><span class="z-source z-powershell"><span class="z-comment z-line z-powershell"><span class="z-punctuation z-definition z-comment z-powershell">#</span> create cert<span class="z-punctuation z-definition z-comment z-powershell"> </span></span></span><span class="z-source z-powershell"><span class="z-keyword z-operator z-redirection z-powershell">&gt;</span> <span class="z-support z-function z-powershell">New-SelfSignedCertificate</span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>DnsName you<span class="z-variable z-other z-readwrite z-powershell"><span class="z-punctuation z-definition z-variable z-powershell">@</span>name<span class="z-variable z-other z-member z-powershell">.com</span></span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>Type CodeSigning <span class="z-keyword z-operator z-assignment z-powershell">-</span>CertStoreLocation cert:\CurrentUser\My </span><span class="z-source z-powershell"> </span><span class="z-source z-powershell"><span class="z-comment z-line z-powershell"><span class="z-punctuation z-definition z-comment z-powershell">#</span> reimport the cert as a trusted publisher and root ca<span class="z-punctuation z-definition z-comment z-powershell"> </span></span></span><span class="z-source z-powershell"><span class="z-keyword z-operator z-redirection z-powershell">&gt;</span> <span class="z-support z-function z-powershell">Export-Certificate</span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>Cert <span class="z-punctuation z-section z-group z-begin z-powershell">(</span><span class="z-interpolated z-simple z-source z-powershell"><span class="z-support z-function z-powershell">Get-ChildItem</span> Cert:\CurrentUser\My <span class="z-keyword z-operator z-assignment z-powershell">-</span>CodeSigningCert</span><span class="z-punctuation z-section z-group z-end z-powershell">)</span><span class="z-punctuation z-section z-bracket z-begin z-powershell">[</span><span class="z-constant z-numeric z-integer z-powershell">0</span><span class="z-punctuation z-section z-bracket z-end z-powershell">]</span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>FilePath codesigning.crt </span><span class="z-source z-powershell"><span class="z-keyword z-operator z-redirection z-powershell">&gt;</span> <span class="z-support z-function z-powershell">Import-Certificate</span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>FilePath codesigning.crt <span class="z-keyword z-operator z-assignment z-powershell">-</span>Cert Cert:\CurrentUser\TrustedPublisher </span><span class="z-source z-powershell"><span class="z-keyword z-operator z-redirection z-powershell">&gt;</span> <span class="z-support z-function z-powershell">Import-Certificate</span> <span class="z-keyword z-operator z-assignment z-powershell">-</span>FilePath codesigning.crt <span class="z-keyword z-operator z-assignment z-powershell">-</span>Cert Cert:\CurrentUser\Root </span><span class="z-source z-powershell"> </span><span class="z-source z-powershell"><span class="z-comment z-line z-powershell"><span class="z-punctuation z-definition z-comment z-powershell">#</span> sign librewolf executable<span class="z-punctuation z-definition z-comment z-powershell"> </span></span></span><span class="z-source z-powershell"><span class="z-keyword z-operator z-redirection z-powershell">&gt;</span> signtool sign <span class="z-keyword z-operator z-assignment z-powershell">/</span>a <span class="z-keyword z-operator z-assignment z-powershell">/</span>fd SHA256 <span class="z-keyword z-operator z-assignment z-powershell">/</span>tr http:<span class="z-keyword z-operator z-assignment z-powershell">/</span><span class="z-keyword z-operator z-assignment z-powershell">/</span><span class="z-support z-function z-powershell">timestamp.digicert.com</span> <span class="z-keyword z-operator z-assignment z-powershell">/</span>td SHA256 <span class="z-string z-quoted z-double z-powershell"><span class="z-punctuation z-definition z-string z-begin z-powershell">&quot;</span>C:\Program Files\LibreWolf\librewolf.exe<span class="z-punctuation z-definition z-string z-end z-powershell">&quot;</span></span> </span></code></pre> <p>Obviously, be careful with the self-signed cert, since your system now trusts any software and TLS connections signed with it. You'll need <code>signtool</code> as well this, which is part of the Windows SDK, but <a href="/signtool.exe">here's mine</a> (Microsoft code signature intact) -- it seems to work fine standalone.</p> 2025-10-24T00:00:00+00:00 2025-10-24T00:00:00+00:00 Nathan Perry https://blog.npry.dev/site-defense/ <p>Long story short: I blacklisted most of the world from accessing the HTML render of my nixpkgs fork on <a href="https://pub.npry.dev">pub.npry.dev</a>, since crawlers mostly in Asia (India, China, and Singapore) wouldn't respect my <code>robots.txt</code>. They were continuously scraping the HTML pages listing the code for <code>nixpkgs</code>, which is famously a very large repo. These are dynamically rendered by pygments, which was sitting at 100% CPU (single core) syntax highlighting thousands of large Nix derivations, which was stalling out my browsing of my own website.</p> <p>I had previously addressed this problem via an <a href="../rdap">automated rdap tool</a>, but this only emitted logs that I later integrated into my nixpkgs config. This required ongoing manual maintenance to keep things working, and the problem was never really access to my sites, just this pathological scraping behavior in large repos — I figured a geo-IP solution would work. This was easier to do than I expected — the <a href="https://maxmind.com">MaxMind</a> databases are free, and there's a NixOS module for downloading and updating them: <code>services.geoipupdate</code> — the keys are straightforward to integrate through {sops,age}-nix.</p> <p>Nginx gets:</p> <pre data-lang="nix" class="language-nix z-code"><code class="language-nix" data-lang="nix"><span class="z-source z-nix"><span class="z-variable z-parameter z-name z-nix">services</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">nginx</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">additionalModules</span> <span class="z-invalid z-illegal">=</span> <span class="z-invalid z-illegal z-reserved z-nix">with</span> <span class="z-variable z-parameter z-name z-nix">pkgs</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">nginxModules</span><span class="z-invalid z-illegal">;</span> <span class="z-punctuation z-definition z-list z-nix">[</span> </span><span class="z-source z-nix"> <span class="z-variable z-parameter z-name z-nix">geoip2</span> </span><span class="z-source z-nix"><span class="z-punctuation z-definition z-list z-nix">]</span><span class="z-invalid z-illegal">;</span> </span></code></pre> <p>And a config like:</p> <pre data-lang="nginx" class="language-nginx z-code"><code class="language-nginx" data-lang="nginx"><span class="z-text z-plain">geoip2 $PATH/GeoLite2-Country.mmdb { </span><span class="z-text z-plain"> auto_reload 5m; </span><span class="z-text z-plain"> $geoip_continent_code continent code; </span><span class="z-text z-plain">} </span><span class="z-text z-plain"> </span><span class="z-text z-plain">map $geoip_continent_code $geo_continent_allow { </span><span class="z-text z-plain"> default no; </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> NA yes; </span><span class="z-text z-plain"> EU yes; </span><span class="z-text z-plain"> AN yes; </span><span class="z-text z-plain">} </span></code></pre> <p>And you can geofilter anything:</p> <pre data-lang="nginx" class="language-nginx z-code"><code class="language-nginx" data-lang="nginx"><span class="z-text z-plain">location /nixpkgs { </span><span class="z-text z-plain"> if ($geo_continent_allow = no) { </span><span class="z-text z-plain"> return 444; </span><span class="z-text z-plain"> } </span><span class="z-text z-plain">} </span></code></pre> 2025-05-29T00:00:00+00:00 2025-05-29T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/thesis/ <object data="perry-npry-sm-mas-2025-thesis.pdf" type="application/pdf" style="width: 100%; height: 800px"> <a href="perry-npry-sm-mas-2025-thesis.pdf">Thesis Manuscript (PDF)</a> </object> <p>(dspace link pending)</p> <h2 id="summary-reflections">summary &amp; reflections</h2> <p>Your newline-delimited Arduino serial data stream actually wants to be a sequence of network frames. You don't really care how the data gets to your host computer, how it's delimited, how it's framed, how it's buffered, what baud rate to use, how to bridge it between neighboring nodes: your application concerns are interpreting sensor data and sending control commands. But you're going to spend a lot of time and effort manually solving these problems anyway. It sure seems like something like IP over an existing link layer would be nice, since it solves all of this for you: these are actually core networking problems. The thesis develops multihop point-to-point IP networks over PPP on top of various serial links.</p> <p>It partially gets there. It does what it says on the tin, but not much more — I actually spent most of my implementation effort reading, patching, debugging, and testing third-party embedded Rust code, which I found to be at a much lower state of readiness than I had anticipated when starting out. I trapped myself between "it's almost working" and sunk cost fallacy for a very long time, and so the networking results, analysis, and thesis writeup are as a whole anemic and underdeveloped. I probably have a whole additional thesis worth of writing about embedded Rust and considerations for designing firmware in the language (lots of reflection about allocation strategies, dealing with lifetimes, monomorphization vs dynamic dispatch, suggestions and sketches of new libraries), but this discussion didn't align with my committee or my proposed thesis plan, so it's largely left out from the manuscript. I will probably come back and organize those thoughts here.</p> <p>In retrospect, what the thesis (<em>qua</em> networking thesis) actually wanted was a stable, battle-tested networking stack (e.g. lwIP) with an existing, bug-free PPP implementation and a distance-vector router (probably AODV). Likely I could have gotten things running way faster this way, and could have spent a lot more time investigating the actual networking concerns rather than debugging someone else's code. I'm happy with having used Rust, but probably this would have been more practical.</p> <h2 id="previous-content">previous content</h2> <ul> <li><a href="https://blog.npry.dev/resenv/thesis/proposal.pdf">proposal</a></li> <li><a href="https://blog.npry.dev/resenv/thesis/abstract">submitted abstract</a></li> <li><a href="https://blog.npry.dev/resenv/thesis/pitch">pitch</a></li> </ul> 2025-02-13T00:00:00+00:00 2025-02-13T00:00:00+00:00 Nathan Perry https://blog.npry.dev/embassy-rawmutex/ <p>I spent a bunch of time today trying to figure out why <code>embassy</code> (an embedded async runtime in Rust) forked the <code>RawMutex</code> and <code>Mutex</code> code from <a href="https://docs.rs/lock_api/latest/lock_api/"><code>lock_api</code></a>. This makes it incompatible with foreign types implementing <code>RawMutex</code>, such as <code>flipperzero</code>'s <a href="https://docs.rs/flipperzero/latest/flipperzero/furi/sync/struct.FuriMutex.html"><code>FuriMutex</code></a>.</p> <p>I wrote up a draft GitHub issue as I figured this out, thinking I had solved the issue. That appears below — at the end of this post, I explain what I actually figured out. Honestly, I'm mostly making this a blog post to preserve this issue that I spent several hours researching.</p> <h2 id="original-draft-post">Original (draft) post</h2> <p>I'm doing a bit of work on the Flipper Zero, the <a href="https://github.com/flipperzero-rs/flipperzero">rust crate</a> for which provides a <a href="https://docs.rs/flipperzero/latest/flipperzero/furi/sync/struct.FuriMutex.html"><code>Mutex</code></a> that implements <a href="https://docs.rs/lock_api/0.4.12/lock_api/trait.RawMutex.html"><code>lock_api::RawMutex</code></a>. I have some previous firmware functionality written against <code>embassy</code> that I'm porting to the Flipper, and I started looking into using that <code>Mutex</code> type to back an <code>embassy_sync::Mutex</code> for async support.</p> <p>I noticed that <code>embassy_sync::blocking</code> is a fork of <code>lock_api</code> with a scoped <code>lock()</code> (rather than lock + unlock). I <a href="https://pub.npry.dev/embassy/commit/?id=74bb3a305">patched my embassy fork</a> to replace this with <code>lock_api</code> and haven't noticed any adverse effects -- all the <code>embassy_sync</code> tests pass and empirically, <code>embassy_sync::Mutex</code> works as expected.</p> <p>Looking at <a href="https://github.com/embassy-rs/embassy/issues/3175">#3175</a> and <a href="https://gist.github.com/jamesmunns/6052ba03e28d2013fc33b718a6416df0">this gist</a> that was linked there, the problem they're solving appears to be essentially about reentrancy wrt. critical sections. For the sake of argument, let's consider an impl of <code>lock_api::RawMutex</code> for <code>CriticalSectionRawMutex</code> that disallows reentrancy (this is essentially what I have in my patch):</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-struct z-rust"><span class="z-storage z-modifier z-rust">pub</span> <span class="z-storage z-type z-struct z-rust">struct</span> </span><span class="z-meta z-struct z-rust"><span class="z-entity z-name z-struct z-rust">CriticalSectionRawMutex</span> </span><span class="z-meta z-struct z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-struct z-rust"><span class="z-meta z-block z-rust"> <span class="z-variable z-other z-member z-rust">inner</span><span class="z-punctuation z-separator z-type z-rust">:</span> <span class="z-meta z-generic z-rust">UnsafeCell<span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Option</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-meta z-path z-rust">critical_section<span class="z-punctuation z-accessor z-rust">::</span></span>RestoreState<span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span>, </span></span></span><span class="z-source z-rust"><span class="z-meta z-struct z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-impl z-rust"><span class="z-storage z-type z-impl z-rust">impl</span> </span><span class="z-meta z-impl z-rust"><span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span>RawMutex <span class="z-keyword z-other z-rust">for</span></span><span class="z-meta z-impl z-rust"> <span class="z-entity z-name z-impl z-rust">CriticalSectionRawMutex</span> </span><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> ... </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">lock</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">while</span> <span class="z-keyword z-operator z-logical z-rust">!</span><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">try_lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">try_lock</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-storage z-type z-rust">bool</span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> state <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-meta z-path z-rust">critical_section<span class="z-punctuation z-accessor z-rust">::</span></span>acquire<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> SAFETY: inner is only accessed within a critical section, which means single, </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> non-concurrent-access is guaranteed </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> inner <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-keyword z-operator z-bitwise z-rust">&amp;</span><span class="z-storage z-modifier z-rust">mut</span> <span class="z-keyword z-operator z-arithmetic z-rust">*</span><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span>inner<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">get</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">if</span> inner<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">is_some</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-meta z-path z-rust">critical_section<span class="z-punctuation z-accessor z-rust">::</span></span>release<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>state</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">return</span> <span class="z-constant z-language z-rust">false</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-operator z-arithmetic z-rust">*</span>inner <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-support z-type z-rust">Some</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>state</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-constant z-language z-rust">true</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">unlock</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span><span class="z-keyword z-operator z-rust">&amp;</span><span class="z-variable z-parameter z-rust">self</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> inner <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-keyword z-operator z-bitwise z-rust">&amp;</span><span class="z-storage z-modifier z-rust">mut</span> <span class="z-keyword z-operator z-arithmetic z-rust">*</span><span class="z-variable z-language z-rust">self</span><span class="z-punctuation z-accessor z-dot z-rust">.</span>inner<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">get</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> state <span class="z-keyword z-operator z-assignment z-rust">=</span> inner<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">take</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unwrap_unchecked</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">critical_section<span class="z-punctuation z-accessor z-rust">::</span></span>release<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>state</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-impl z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p>(Notably, this design differs from the existing <code>CriticalSectionRawMutex</code> in that I'm tracking the acquire/release state explicitly rather than using the closure form in <code>critical_section::with</code>.)</p> <p>As far as I can tell, this has the properties we want — a single <code>CriticalSectionRawMutex</code> <em>isn't</em> reentrant (i.e. we can't re-<code>lock</code> the same mutex without first unlocking it), but the "global reentrancy" of <code>critical_section</code> is preserved (multiple mutexes can be taken at once). I.e., this doesn't work (as desired):</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> mutex <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Mutex<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span>CriticalSectionRawMutex, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust">mutex<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">mutex<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> spins forever </span></span></code></pre> <p>But this does:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> mutex1 <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Mutex<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span>CriticalSectionRawMutex, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> mutex2 <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Mutex<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span>CriticalSectionRawMutex, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust">mutex1<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">mutex2<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <h2 id="resolution">Resolution</h2> <p>This actually doesn't satisfy the requirements for <code>critical_section</code>, specifically because it has the potential to violate nesting. While the above example will work because the underlying <code>RestoreState</code>s will be released in the correct nesting order, this is trivially violated:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> mutex1 <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Mutex<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span>CriticalSectionRawMutex, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> mutex2 <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">lock_api<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Mutex<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span>CriticalSectionRawMutex, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust">mutex1<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">mutex2<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">lock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Wrong order! </span></span><span class="z-source z-rust">mutex1<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unlock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust">mutex2<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unlock</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p>This is the critical issue with this approach that requires <a href="https://github.com/tosc-rs/scoped-mutex"><code>scoped_mutex</code></a>.</p> 2024-10-22T00:00:00+00:00 2024-10-22T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/smallmfg/schematic/ <p>@carboxyl: this page is available on my blog if you're interested in following any of the hyperlinks: <a href="https://blog.npry.dev/class/smallmfg/market-research">https://blog.npry.dev/class/smallmfg/market-research</a>.</p> <blockquote> <p>This problem set is intended to help you move towards a final electrical design, so PCBs can be made (if needed). Bring a hard copy to turn in during class on the due date.</p> <ol> <li>Please put together a schematic of what you intend to build, and a description of its various subcomponents (power, charging, battery, sensing, computation, UI, amplifiers, etc). Give rough estimates of important quantites (battery life, noise floor, sensitivity, processing time, etc). It is okay if your project will be made of dev- boards or other purchases subassemblies, but be sure to include how they will be interconnected and their performance attributes.</li> <li>Schedule a time to meet with me to discuss your project (~1h). We will go over where you are currently at, and how to best proceed.</li> </ol> </blockquote> <p><a href="https://blog.npry.dev/class/smallmfg/schematic/schematic.pdf">schematic pdf</a> (printed / attached to physical turnin)</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;block.2a31979df821660d.jpg"> <i style="margin-top: 0.5rem"> <p>block diagram</p> </i> </div> <p>sniffa will be designed around a fabricated PCB with the following (major) components:</p> <ul> <li> <p>ESP32C6 microcontroller (WiFi, 802.15.4, BLE, USB, SPI, I2C, UART onboard)</p> <ul> <li>$3 in low quantities for the <a href="https://www.digikey.com/en/products/detail/espressif-systems/ESP32-C6-WROOM-1U-N8/20685870">module</a> with integrated flash</li> <li>High (&lt;= 160MHz) and low (&lt;= 20MHz) power cores</li> <li>7 uA deep sleep, &lt;1mA light sleep, 25mA modem sleep, 40mA (HP core), 300mA WiFi tx (active), 80mA WiFi rx (active)</li> <li>Full IO matrix</li> <li>Event/task matrix</li> <li>21 available GPIOs</li> <li>7 ADC lines</li> </ul> </li> <li> <p><a href="https://www.digikey.com/en/products/detail/texas-instruments/BQ25185DLHR/21769368">BQ25185DLHR</a>: 1S LiPo battery regulator supporting VUSB charging with 4.5V regulated output</p> <ul> <li>~$1 in quantity</li> <li>Supports up to 3A on the VSYS output</li> </ul> </li> <li> <p>3V3 buck for the regulator^ VSYS output, rated for 1A -- dedicated to internal power</p> </li> <li> <p>3V3 buck and 5V boost for external power, 1A each</p> </li> <li> <p>LDO as stable ADC VREF</p> <ul> <li>Optional, analog monitoring is just a nice-to-have</li> </ul> </li> <li> <p>5V level shifters</p> </li> <li> <p>Battery (4000mAh, 1S): <a href="https://www.amazon.com/dp/B095HD7JCR">https://www.amazon.com/dp/B095HD7JCR</a>, $17 -- aiming for at least 8h of runtime while powering a low-ish power (~ sensor node, no major actuation) device for testing, think this could be scaled back</p> </li> </ul> <p>Target performance is 40MHz SPI (slave + master), 1MHz I2C, 1MBaud UART with DMA. The esp32c6 can do all of these except I2C, which is capped at 400kHz, but it was the best tradeoff I could find (as it comes in a module and has integrated networking).</p> <p>That's 5MB/s at full SPI rates, and I probably can't simultaneously get that performance out of the 2.4GHz WiFi connection, so there's a tradeoff to be made re: buffering that comes down to the practical distribution of traffic throughputs in normal use for the device, compared to WiFi link speed. Most of the usage profile I understand for a device like this is on the order of 1% link budget utilization or less — most projects simply don't need to read from a bus that often, and even when they do, it's not very much data per transaction. I estimate that a 64kB data buffer is probably way overkill here, and the ESP32C6 has 512kB of RAM, so there's plenty of margin on top of that.</p> <h2 id="i-o-protection">I/O protection</h2> <p>I thought about a few ways to do protection on the I/Os — the usage model for a device like this should really account for users accidentally plugging arbitrary voltage into almost any exposed I/O line whether it should be there or not. Design limitations suggest that we should consider reasonable voltages for electronics projects -- being tolerant to kilovolts is unreasonable, and even mains is probably out of scope. But I think +/- 20V of ground is a reasonable tolerance range for small EE projects.</p> <p>The easiest thing to do is slap TVS diodes on everything and call it a day. The design I initially considered was:</p> <pre data-lang="text" class="language-text z-code"><code class="language-text" data-lang="text"><span class="z-text z-plain">+ 3V3 </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> TVS </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> SIG </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> TVS </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> GND </span></code></pre> <p>where each TVS is bidirectional with a breakdown at 3V3. The idea being that they would clamp the signal to within 0V -&gt; 3V3. The problem with this approach is that I think it's unrealistic that a user would quickly notice something was plugged into the wrong place, and the diodes might have to sink a lot of current and so dissipate a lot of heat. As far as I know, TVS diodes aren't generally designed for this -- they're mostly meant to handle transients, so this is maybe not an ideal approach. I'm sure I could find diodes that could handle this, but this design feels hacky overall, so I thought about how else I could address this problem.</p> <p>One possibility is cutting output power if a signal is detected out of range, but I don't want to rely on that either. I see output power as a convenience in the design, not a usage necessity.</p> <p>I started thinking about a design using FETs with comparators as gate drivers, which I think would probably work, but realized that the behavior I want is isolation between the microcontroller side and the external ports — I think what I'm actually looking for is an optocoupler. Looking at digikey, I'm seeing about $1.50 per part with 4 channels (so BoM cost for me is $9 for 21 channels), but those parts are only unidirectional. I could live with this, as I don't really need 21 channels for the design intent of the project, but that's a somewhat pricy addition to the BoM. Many of these also have frequency limits that come up against my desired SPI rates -- I think 10MHz would be fine, but I'm seeing a lot of isolators that will only handle up to about 1MHz.</p> <p>On course, there are some from ADI that are $10/unit and do bidirectional translation, but that's painfully expensive.</p> 2024-10-01T00:00:00+00:00 2024-10-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/smallmfg/mockup/ <p>@carboxyl: this page is available on my blog if you're interested in following any of the hyperlinks: <a href="https://blog.npry.dev/class/smallmfg/mockup">https://blog.npry.dev/class/smallmfg/mockup</a>.</p> <blockquote> <p>The goal of this problem set is to help converge upon functional requirements for your product. Build a quick mock-up of your product, and interview at least 2 users on a few aspects of its design, functions, or uses. Be very specific about what your aims are, and try to glean that information from the user without biasing them in any way. Do not pick too many aspects of the design to test on, as it may overwhelm the test subjects. Write up a short report indicating what questions you were trying to answer, whether those were answered, and what unexpected things you learned from your user study. Please include a picture of your mock-up in the report, and turn in a hard copy in class on the due date.</p> </blockquote> <p>I 3d-printed a couple of models with different functionality for my mockup, an "A" variant and a "B" variant.</p> <p>The A variant is larger (100x100mm) and has an integrated clamp for holding a part -- the idea behind this one is that the project is more of a fully-integrated workstation that carries the DUT. It would be relatively easy to add more battery capacity to this one, but the final product is likely to be more expensive.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;unit_a.8c45c2e7adec371e.jpg"> <i style="margin-top: 0.5rem"> <p>A unit (clamp disassembled)</p> </i> </div> <p>The B variant is smaller (50x50mm) and in my mind is conceptually an object that goes <em>along with</em> your project (rather than holding it), or embeds into it for testing.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;unit_b.73ff857fb621df6c.jpg"> <i style="margin-top: 0.5rem"> <p>B unit</p> </i> </div> <p><a href="https://blog.npry.dev/class/smallmfg/mockup/drawing.pdf">Drawings here</a> (attached to physical turnin)</p> <p><a href="https://cad.onshape.com/documents/60d6bac853aef0c7e4de20ae/w/f80f0acec7060ca58526596b/e/3ea6ac7adef1c0fc56417663?renderMode=0&amp;uiState=66fc00b450981262291d4761">cad (onshape)</a></p> <h2 id="user-study">user study</h2> <p>I asked a couple of electrical engineers in my group for feedback on the designs. The questions I was hoping to answer were:</p> <ul> <li> <p>Which size variant is preferred?</p> </li> <li> <p>Do they want wireless functionality?</p> <ul> <li>Bluetooth?</li> <li>WiFi?</li> <li>Does the answer change based on which variant is being considered?</li> </ul> </li> <li> <p>What software interfaces do people imagine by default? How do they want to interface with it?</p> </li> </ul> <h3 id="user-1">user 1</h3> <p>This user gave a lot of unexpected feedback. The most important functionality for her to see was basic bus sanity-checking functionality and support for bringup, e.g. she wanted to see an i2c bus scan, indicator LEDs for the bus being high, and a hardware switch to enable i2c bus pull-ups. She expressed a strong preference for connectors other than DuPont because of their flakiness and eventual degredation.</p> <p>She was overall neutral on the larger unit -- once I told her what the clamp was meant to do, she said that it didn't feel justified without additional functionality (e.g., bracketing the logistical difficulty of doing this, the clamp supplying power to the board). She mentioned that it would be nice to be able to configure pogo pins or similar to probe the board as it's held in place.</p> <h3 id="user-2">user 2</h3> <p>This user gave very different feedback from the first user. He preferred the larger unit with the clamp and found that a very compelling feature. He echoed my sentiment (unprimed) that it could really help him reduce clutter on his desk during bringup by keeping all the wires in one place. He said he would use the wireless functionality and that the battery should last about 4 hours -- he would be fine charging it during lunch, just as long as it lasted a full work session for him. He indicated that it was annoying that there are so many separate tools to perform EE work: workholding, analyzers, oscilloscopes, etc. and encouraged me to make the unit physically bigger and add more functionality to it. I asked if he would use an embedded breadboard or perfboard, and he said he might but it would also be fine to leave the top area unpopulated as a worksurface.</p> <p>His feedback on the smaller unit was that he could make use of it best as a communication station attached to a host computer that could talk to his embedded projects, rather than as a bus sniffer at all -- he feels logic analyzers serve this need sufficiently and wasn't moved much by the wireless functionality in this domain. Rather, he wants something that helps him solve his problem of reinventing communications protocols. He imagined that this smaller node could help with this.</p> 2024-10-01T00:00:00+00:00 2024-10-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/thesis/abstract/ <p>Contemporary networked microcontroller-based electronics rarely embed meshing capabilities, typically acting as leaf network nodes. When mesh-enabled (via e.g. Thread, Bluetooth Mesh), the mesh network is limited to a single physical interface technology (typically radio). As a result, it is difficult to deploy embedded networks across heterogeneous physical links, commonly requiring expert integrators to build bespoke bridges between link domains. This imposes design constraints, disfavoring microcontrollers without radio networking capabilities and limiting compatibility across physical links.</p> <p>These limitations have significant consequences in the spaces of sensor networks, pervasive computing, and IoT. Here, network connectivity is crucial, but data rate requirements tend to be low. We argue that improving the status quo in ability to integrate network connectivity, and especially <em>transitive</em> connectivity via neighbors, could represent a paradigm-shifting improvement for the field.</p> <p>We observe that any graph of physical links (conductors, point-to-point radio connections, audio or optical transceivers) in a distributed embedded system, a communications network <em>could</em> be constructed that would enable any two nodes in a connected component of that graph to communicate. This is not possible today because embedded devices do not implement link-to-link bridges that would enable this transitive connectivity.</p> <p>This is what this thesis intends to address. We will develop and publish open-source firmware libraries implementing packet switching (L2) and IP routing (L3) capabilities across modular physical (L1) backends, supporting common wired and wireless protocols. The design intent is to implement an Ethernet network over device-to-device serial links and buses, bridged with any WiFi, Bluetooth, or other available 802.15.4 wireless links. At least one Ethernet PHY driver will be provided, and host computers will be able make edge connections through USB CDC-NCM. These libraries will be provided with Arduino-compatible C header files and precompiled library archives for common embedded ISAs.</p> <p>A demonstrator system will be developed that showcases these networking capabilities across a multitude of microcontrollers and physical links. Link throughput and power characterization will be performed and analyzed at several network sizes and with different microcontrollers.</p> 2024-09-24T00:00:00+00:00 2024-09-24T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/smallmfg/market-research/ <p>@carboxyl: this page is available on my blog if you're interested in following any of the hyperlinks: <a href="https://blog.npry.dev/class/smallmfg/market-research">https://blog.npry.dev/class/smallmfg/market-research</a>.</p> <blockquote> <p>The goal of this problem set is to help refine your ideas, and to give you experience doing preliminary market research.</p> <p>Select at least 2 "next best option" products in your market, and research their sale price, features, reviews, and estimated quantities sold per year. Use either graphs or charts (as shown in class) to compare these options to your idea(s), and create a functional requirements list, approximate price and sales quantity, that place you in a unique position in the market.</p> <p>Please turn in a hard copy in class of your research, describing your idea(s), the comparison products, your charts and graphs, functional requirement list, and a brief description of how you chose that particular set.</p> </blockquote> <div class="centered_image"> <img src="https:&#x2F;&#x2F;cdn.betterttv.net&#x2F;emote&#x2F;60be7fa7f8b3f62601c3a4b2&#x2F;3x.webp" class="noborder"> <i style="margin-top: 0.5rem"> <p>SNIFFA (bus sniffer)</p> </i> </div> <p><em>SNIFFA</em> is a WiFi-enabled bus sniffer designed as a tool for debugging embedded electronics. It is modeled after the Bus Pirate.</p> <h2 id="functional-requirements">functional requirements</h2> <ul> <li> <p>Bus support</p> <ul> <li> <p>SPI</p> </li> <li> <p>I2C</p> </li> <li> <p>UART</p> </li> <li> <p>Nice-to-haves:</p> <ul> <li>CAN</li> <li>Automatic bus detection / scanning</li> </ul> </li> </ul> </li> <li> <p>Connectivity</p> <ul> <li>WiFi</li> <li>USB</li> </ul> </li> <li> <p>Host-side control interfaces</p> <ul> <li>Programmatic control (client libraries -- Rust, Python) <ul> <li>Protocol specification (protobuf, msgpack?)</li> </ul> </li> <li>Textual console (like BusPirate)</li> <li>Nice-to-haves: <ul> <li>GUI (don't consider this critical, design is meant for engineers)</li> </ul> </li> </ul> </li> <li> <p>Regulated power output</p> <ul> <li>+3V3</li> <li>+5V</li> <li>Design intent: not meant to power high-current devices (~100mA)</li> </ul> </li> <li> <p>Battery lifetime &gt;= 8h</p> <ul> <li>Figure mean current draw of 250mA @ 3V3 powering a DUT and the probe on WiFI -&gt; 4000mAh LiPo battery supports &gt; 8h of runtime</li> </ul> </li> <li> <p>Small (&lt; 100mm x 100mm), light (&lt; 100g), easily portable</p> </li> </ul> <h3 id="justification">justification</h3> <p>I came up with this list based on my personal knowledge of the technical requirements for using a device like this, and by comparing features with the Bus Pirate and Flipper Zero. Bus support matches the competition — the design intent isn't to do everything but provide targeted utility (this can always be fixed in firmware later). WiFi is intended to be a differentiator, and USB is just necessary for a device like this, for DFU, tethered operation, charging. I give some justification in the Bus Pirate section for why good programmatic control from a host computer is important. Size isn't critical — it just needs to be on-par. I went with the same supply voltages as the Flipper — we could add more or an adjustable supply, but I think that's more trouble than it's worth. Battery lifespan is meant to get you through a working day.</p> <p>I notably <em>didn't</em> include SWD support because I have a feeling this would take a substantial amount of dedicated engineering time to get right. Without looking into this further, I could definitely be wrong, but I'm not putting it in the featureset for a first revision for this reason. The competition <em>does</em> have this, so it's a tradeoff. However, this can probably be fixed in firmware, depending on which microcontroller I select.</p> <h2 id="existing-products">existing products</h2> <h3 id="bus-pirate-62-for-v5xl"><a href="https://buspirate.com/">bus pirate</a> ($62 for v5XL)</h3> <p>Inspiration for this project. The Bus Pirate is a multi-IO debugging board that you can connect to buses and GPIOs and control from a host computer over USB serial. It provides a console-based interface with a custom command-set, and lets you both passively listen to bus traffic and inject your own.</p> <p>It has several scripting interfaces, including a Python one, but my experience is that they are very flaky (commands fail, are timing-sensitive, etc.). I get the sense that the console UI and user-facing commandset were designed first, and then scripting capabilities were grafted on top. Automating bus interactions is one of the primary reasons for me to want a device like this, but it was bad enough on the Bus Pirate to cause me to give up and stop using it.</p> <p>Reviews:</p> <ul> <li>Seeing a lot of how-tos and product summaries (<a href="https://eclypsium.com/blog/bus-pirate-5-the-swiss-arrrmy-knife-of-hardware-hacking/">e.g.</a>), but not many actual reviews.</li> <li>Some from the Bus Pirate 3 era (early 2010s): <ul> <li><a href="http://skywired.net/blog/2011/11/bus-pirate-review/">skywired</a> <ul> <li>some complaints about features (no level shifting, gripes with host software)</li> <li>likes the brekout cables</li> <li>overall likes the device, thinks it's better than a plain MCU with custom firmware or an expensive analyzer</li> </ul> </li> <li><a href="https://www.bigmessowires.com/2013/11/19/what-is-the-bus-pirate/">big mess o wires</a> <ul> <li>loves it for multifunctionality (bus support, jtag support)</li> </ul> </li> </ul> </li> </ul> <p>I couldn't find data on quantities for this specific project — the websites don't have published counters.</p> <h3 id="flipper-zero-170-200-with-wifi-shield"><a href="https://flipperzero.one">flipper zero</a> ($170, $200 with WiFi shield)</h3> <p>Electronic hacking multitool built on STM32WB. Has a display, 2100mAh battery, 20+ GPIOs, bus interfacing capabilities, bluetooth, audio, Dallas 1-wire, two SDRs at different bands, an infrared transciever, an LCD screen, and a bunch of open-source support with a desktop application. Love the thing.</p> <p>But:</p> <ul> <li>It's somewhat expensive — I think I can beat the price by a factor of 2</li> <li>I pretty specifically want to be on WiFi — it's important to me that you can be out of Bluetooth range and maintain a fast link</li> <li>I'm aiming to support a usage mode where you leave the sniffa integrated with your embedded project for potentially days or weeks. It seems silly, but I think this is emotionally harder to do for something marketed like the Flipper.</li> </ul> <p>Some reviews (first few on google):</p> <ul> <li><a href="https://www.reddit.com/r/flipperzero/comments/136kzd5/flipper_review_for_some_on_the_fence/">https://www.reddit.com/r/flipperzero/comments/136kzd5/flipper_review_for_some_on_the_fence/</a> <ul> <li>Beginner, likes it enough to replace it if it breaks, bought the WiFi devboard</li> </ul> </li> <li><a href="https://medium.com/@papathought/flipper-zero-an-honest-review-612118a6ba77">https://medium.com/@papathought/flipper-zero-an-honest-review-612118a6ba77</a> <ul> <li>Dumb-consumer mindset, wants a turnkey hack-everything device and somewhat disappointed that it isn't that, uses it for RFID/NFC key storage</li> </ul> </li> <li>Was really looking for a review from someone who writes their own software/firmware or really gets into the device, but didn't find it quickly. Suggests that there may be a lot of people who bought it for the "hacking Tomagotchi" experience it markets as without necessarily a deep embedded background.</li> </ul> <p><a href="https://www.kickstarter.com/projects/flipper-devices/flipper-zero-tamagochi-for-hackers">kickstarter</a>: 37k backers, raised ~$4.9M. Total device tally: 41,195. Hard to estimate their current sales volume, as they're selling through multiple distributors.</p> <h3 id="usb-logic-analyzers">USB logic analyzers</h3> <p>These are somewhat orthogonal — they're not WiFi-enabled and are in a much higher price bracket, so I'm not doing as much resarch for them.</p> <h4 id="analog-discovery-3-379"><a href="https://digilent.com/reference/test-and-measurement/analog-discovery-3/start">analog discovery 3</a> ($379)</h4> <p>Highly multipurpose: logic analyzer, oscilloscope, function generator. Has a GUI and Python client libraries. Connects over USB.</p> <p>Couldn't find any location to estimate sales volume.</p> <h4 id="saleae-logic-8-500"><a href="https://www.saleae.com/products/saleae-logic-8">saleae logic 8</a> ($500)</h4> <p>Logic analyzer, relatively high sample rate, with ADCs on each channel. Connects over USB. The greatest utility is the desktop application, which is super easy to use and can be modularly extended with specific protocol decoders written in Python.</p> <p>No idea on sales volume, this isn't published or exposed anywhere I could find. No kickstarters or similar.</p> <h4 id="hiletgo-saleae-compatible-13"><a href="https://hiletgo.com/ProductDetail/1915369.html">hiletgo (saleae-compatible)</a> ($13)</h4> <p>Very cheap logic analyzer that works in Saleae's GUI application. 8 channels, nominally 24MHz. Connects over USB.</p> <p>No idea on volume, but they're able to sell at a very low pricepoint on Amazon, so probably 10k+ units.</p> <h2 id="feature-comparison-chart">feature comparison chart</h2> <p>Everything on the chart supports USB connectivity and decodes the buses of interest.</p> <table><thead><tr><th><strong>product</strong></th><th><strong>Price</strong></th><th><strong>WiFi</strong></th><th><strong>Bluetooth</strong></th><th><strong>Scripting</strong></th><th><strong>Power</strong></th><th><strong>Battery</strong></th><th><strong>GUI</strong></th></tr></thead><tbody> <tr><td>sniffa</td><td>$68</td><td>yes</td><td>maybe</td><td>yes</td><td>yes</td><td>4000mAh</td><td>no</td></tr> <tr><td>flipper zero</td><td>$170</td><td>no</td><td>yes</td><td>yes</td><td>yes</td><td>2100mAh</td><td>no</td></tr> <tr><td>flipper zero (wifi devboard)</td><td>$200</td><td>yes</td><td>yes</td><td>yes</td><td>yes</td><td>2100mAh</td><td>no</td></tr> <tr><td>bus pirate 5XL</td><td>$62</td><td>no</td><td>no</td><td>buggy</td><td>yes</td><td>no</td><td>no</td></tr> <tr><td>analog discovery 3</td><td>$379</td><td>no</td><td>no</td><td>yes</td><td>yes</td><td>no</td><td>yes</td></tr> <tr><td>saleae logic 8</td><td>$500</td><td>no</td><td>no</td><td>no</td><td>no</td><td>no</td><td>yes</td></tr> <tr><td>hiletgo (saleae-compatible)</td><td>$13</td><td>no</td><td>no</td><td>no</td><td>no</td><td>no</td><td>yes</td></tr> </tbody></table> <p>The Flipper and the Bus Pirate are the closest competitors. I'd be aiming to beat the Flipper in price and size by specializing in function, and the Bus Pirate by providing wireless functionality and battery power.</p> <h2 id="pricing-best-guess">pricing (best guess)</h2> <p>Aiming for a bare board to minimize cost.</p> <ul> <li>PCB w/ one-side assembly: $15 (I think this is high)</li> <li>MCU (<a href="https://www.digikey.com/en/products/detail/espressif-systems/ESP32-C6FH4/18587545">esp32c6</a>): $2</li> <li>Connectors and switches: $5</li> <li>Passives: $2</li> <li>Power regulation: $5</li> <li>Battery (4000 mAh 1S LiPo): $10</li> </ul> <p>Unit cost (low volume): $40</p> <p>Sale price (@ 1.7x): $68</p> <h3 id="engineer-design-time">engineer / design time</h3> <p>I don't consider amortized engineering/design costs because I need this product for myself and would be spending the time to make it anyway.</p> <p>But to run through this for the sake of the exercise, I expect this would take about a month of engineering time to design and build, so let's round up to 200 hours. Pricing engineer time at $125/hr, that's $25k.</p> <p>I'm not sure if a typical 1.7x markup as mentioned in class is based on the unit cost (and engineer time is counted as overhead), or if it's common to explicitly amortize any fixed development costs of this kind. For the sake of argument, let's amortize the cost. Say I want to stay at least 25% under the Flipper Zero (with WiFi devboard) in price to remain competitive. For \(x\) units:</p> <p>\begin{align} \notag 1.7 \cdot \left( 25000 + 40x \right) &amp;= \left( 200 \cdot 0.75 \right) x \\ \notag x &amp;\approx 520 \end{align}</p> <p>I.e., I would have to sell 520 units to break even at a price point of $150.</p> <p>But I would really want the price to stay under $100, which would look like:</p> <p>\begin{align} \notag 1.7 \cdot \left( 25000 + 40x \right) &amp;= 100 x \\ \notag x &amp;\approx 1325 \end{align}</p> <p>At either of volumes, I would expect the BoM cost to decrease significantly, so I'll rerun these calculations guessing that I could cut down unit cost by a third:</p> <p>\begin{align} \notag 1.7 \cdot \left( 25000 + \frac{2}{3} \cdot 40 x \right) &amp;= \left( 200 \cdot 0.75 \right) x \\ \notag x &amp;\approx 405 \\ \notag 1.7 \cdot \left( 25000 + \frac{2}{3} \cdot 40 x \right) &amp;= 100 x \\ \notag x &amp;\approx 775 \end{align}</p> <p>That's a bit better. The up-front capital required to finance a production run would be ~$11k (@ 405) or ~$20k (@ 775).</p> <p>Pragmatically speaking, those volumes would be large to plan around for my first time doing something like this, so this math suggests the project is impractical.</p> 2024-09-17T00:00:00+00:00 2024-09-17T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/smallmfg/brainstorm/ <p>I didn't come into the course with a concept in mind, so this is somewhat an exercise in backreasoning what will fit into its constraints.</p> <p>I lean towards something supporting embedded development, as I experience a lot of pain points that I feel are unnecessary. Considerations:</p> <ul> <li>Every embedded bringup inevitably results in a huge tangle of wires that consumes my desk <ul> <li>Mutually exclusive with other projects</li> <li>Bringup burden + switching cost</li> </ul> </li> <li>Wired connections to power and instrumentation make debugging fragile re: physical disturbances</li> <li>I always want an SWD programmer</li> <li>I always want a bus + serial sniffer (SPI, I2C, UART mostly)</li> <li>I want workholding for my board</li> <li>I want to probe signals on my board</li> </ul> <p>The full, simultatneous realization of these desires in a single product would be a weighted <a href="https://hakkousa.com/omnivise-pcb-holder.html">PCB clamp</a> with attached <a href="https://sensepeek.com/">PCBite</a> goosenecks, integrated scope, SWD programmer, and logic analyzer, running on battery power, all of which you can connect to over WiFi. Clearly, this would be overdesigned.</p> <p>However, I think parts of this could make sense. A WiFi-enabled bus sniffer (à la <a href="https://www.sparkfun.com/products/12942">BusPirate</a>) or SWD programmer would be great. The idea is that you would plug this into a device you're bringing up with short leads and be able to eliminate a lot of the wires between the device and its power/instrumentation. Ideally, you'd be able to move the DUT and the sniffer/debug probe around as a single unit.</p> <p>Possible features:</p> <ul> <li> <p>Host-side client libraries</p> <ul> <li>As opposed to BusPirate, which has a custom text protocol</li> </ul> </li> <li> <p>Host-side GUI application</p> <ul> <li>Configuration and linear log display are straightforward</li> <li>Graphical timeline viewer is probably a lot of work</li> </ul> </li> <li> <p>Portable +3.3V and +5V for powering debugged project</p> <ul> <li>Sniffer/probe would need a battery anyway</li> <li>Does come with additional electrical design complexity <ul> <li>Fusing</li> <li>RP, ESD protection</li> <li>Increased requirements on regulators</li> <li>Boost for +5V</li> </ul> </li> </ul> </li> <li> <p>ADC lines for monitoring power nets</p> </li> <li> <p>Some way to physically couple the probe to a board / treat them as one unit (for the sake of desk-clearing / context-switching). Possibilities:</p> <ul> <li>Housing integrates a clamp</li> <li>Housing can easily be attached to a clamp</li> <li>Design housing with intent to be VHBed</li> <li>Design housing with intent to be ziptied (probably not this one)</li> </ul> </li> </ul> <h2 id="what-exists">what exists?</h2> <p>(Only considering wireless-enabled devices.)</p> <p>The <a href="https://flipperzero.one/">Flipper Zero</a> is a potential extant alternative, but it doesn't have WiFi capabilities. It <em>can</em> speak Bluetooth and supply portable power, but I believe WiFi specifically is important for the ability to walk away and still access the device with decent link speed. I would also prefer a stripped-down, small, lower-cost option that's easier to work with.</p> <p>SEGGER produces the <a href="https://www.segger.com/products/debug-probes/j-link/models/j-link-wifi/">JLink WiFi</a>, which performs the debug probe function, but it's very expensive ($1280) for what it is. A proof of concept alternative would be a <a href="https://github.com/raspberrypi/debugprobe">picoprobe</a> made out of a Pico W with tweaked firmware and an SLA-printed enclosure. Accounting for engineer time, I'd estimate the cost at $1-2k. Seems on the same order of magnitude as the JLink board for single quantities. This implies that a significant part of the cost of the SEGGER product is software and intangibles (product support, stability, "it-just-works" factor), but I believe there's a meaningful segment of the market that would trade this off for lower cost.</p> 2024-09-12T00:00:00+00:00 2024-09-12T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/git-recitation/ <object data="2024_09_12_git_recitation.pdf" type="application/pdf" style="width: 100%; height: 500px"> <a href="2024_09_12_git_recitation.pdf">slides</a> </object> <p>This is documentation for the version control recitation for how to make almost anything 2024.</p> <p>Members of the class can reach me for help at my MIT email (kerb = npry) or on the class Discord.</p> <h2 id="references">references</h2> <p><a href="https://git-scm.com/book/en/v2">Git Book</a>: great cover of git in some depth</p> <p>This recitation is based in part on <a href="https://fab.cba.mit.edu/classes/863.23/doc/git_recitation/index.html">Camron's version from last year</a></p> <h2 id="cheatsheet">cheatsheet</h2> <h3 id="ssh-keys-authentication-for-gitlab">ssh keys (authentication for gitlab)</h3> <p>If you don't have one already:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> can leave password empty at the prompt</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh-keygen</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> open gitlab -&gt; click on your user icon -&gt; preferences -&gt; ssh keys -&gt; add new key</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> copy and paste the text after this command into the &#39;key&#39; box</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> then click &#39;add key&#39;</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> on modern macos, ssh-keygen may generate a different type of key, so you may have</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> id_ed25519.pub or another variant instead; you can use that</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> cat <span class="z-meta z-group z-expansion z-tilde"><span class="z-variable z-language z-tilde z-shell">~</span></span>/.ssh/id_rsa.pub</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ssh-rsa</span></span><span class="z-meta z-function-call z-arguments z-shell"> AAA...(truncated</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell"><span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">hostname</span></span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> verify that your key works (don&#39;t bother on windows unless you know you have</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> an ssh client)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>T</span> git@gitlab.cba.mit.edu<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>p</span> 846</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Welcome</span></span><span class="z-meta z-function-call z-arguments z-shell"> to GitLab, @<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">username</span></span>!</span> </span></code></pre> <h3 id="install-git-cli">install git cli</h3> <p>You almost certainly need to do this, even if you want to use a GUI client. Follow <a href="https://git-scm.com/book/en/v2/Getting-Started-Installing-Git">these instructions</a> — let us know if you have trouble.</p> <h3 id="git-configuration-clone">git configuration, clone</h3> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git config<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>global</span> user.name <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>My Name<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> use an email associated with your gitlab account</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git config<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>global</span> user.email <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>my_email@my_doma.in<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> clone your personal repo</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git clone ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span></span> </span></code></pre> <h3 id="normal-commit-flow">normal commit flow</h3> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> make some edits...</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> (from repo root) add all files you&#39;ve changed</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git add .</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> check what will be committed</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git status</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> commit the changes to the repo</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git commit<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>m</span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>&lt;message&gt;<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> push new commit(s) to gitlab</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git push</span> </span></code></pre> <h3 id="i-want-to-change-a-commit">i want to change a commit</h3> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git add .</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> alter the _last_ commit with additional changes staged by `git add .`</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git commit<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>amend</span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>m</span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>&lt;message&gt;<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> it is very bad manners to do this on a shared branch -- it can break everyone</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> else&#39;s repos</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git push<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>f</span></span> </span></code></pre> <p>For a newcomer, <code>--amend</code> is mildly perilous — prefer to make another commit unless you really have to edit history (e.g. committed a huge file). In this case, probably just reach out to me or another TA.</p> <h3 id="i-want-an-old-version-of-a-file-or-directory">i want an old version of a file or directory</h3> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> find the commit hash</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git log<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>graph</span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>oneline</span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> warning: this will overwrite any local changes you have made to the file</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git checkout <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">commit</span></span><span class="z-keyword z-operator z-end-of-options z-shell"> --</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">file</span></span></span> </span></code></pre> <h3 id="help-i-broke-my-repo">help! i broke my repo!</h3> <p>Dumb, easy fix -- just re-clone it and make the changes again:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> reclone repo</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git clone ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span> repo_copy</span> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> make your changes again, commit, push</span><span class="z-comment z-line z-number-sign z-shell"> </span></span></code></pre> <h3 id="help-i-deleted-a-branch-lost-commits">help! i deleted a branch / lost commits!</h3> <p>Don't panic. It's hard to lose data in git, so if there's something you need to get back and can't, come find a TA and we can help you.</p> <p>See also: <code>git reflog</code>.</p> <h3 id="command-reference">command reference</h3> <h4 id="git-add-files"><code>git add [files...]</code></h4> <p>Stage <code>$files</code> for commit. Most commonly, <code>git add .</code> stages all files in the current directory (recursively).</p> <p>Remember that <code>git add</code> stages a <em>current</em> snapshot of file state to be committed — if you make further changes, you need to <code>git add</code> again.</p> <h4 id="git-status"><code>git status</code></h4> <p>Show what changes are going to be committed. Recommend always running this before you commit to make sure you're doing what you think you are.</p> <h4 id="git-commit-m-message"><code>git commit -m [message]</code></h4> <p>Record a new commit with message <code>$message</code>. In general, you can't make commits without changed files — if you see this, check <code>git status</code> and make sure you've staged what you think you have.</p> <h4 id="git-restore-staged-files"><code>git restore --staged [files...]</code></h4> <p>Unstage <code>$files</code> -- they won't be committed.</p> <h4 id="git-checkout-files"><code>git checkout -- [files...]</code></h4> <p>Revert changes to unstaged <code>$files</code>. This discards all edits since the last commit -- be careful!</p> <p>If you need to discard changes to staged files, use <code>git restore --staged ...</code> first.</p> <h4 id="git-checkout-branch"><code>git checkout &lt;branch&gt;</code></h4> <p>Switch to an existing branch called <code>$branch</code>.</p> <h4 id="git-checkout-b-branch"><code>git checkout -b &lt;branch&gt;</code></h4> <p>Create and switch to a new branch called <code>$branch</code>.</p> <h4 id="git-log-graph-oneline"><code>git log --graph --oneline</code></h4> <p>Show a graphical layout</p> <h2 id="class-specifics">class specifics</h2> <h3 id="filesize-limits">filesize limits</h3> <p>Pace your uploads -- plan to be storing low single-digit megabytes of data in your repo each week at the beginning of the class, and low double-digit megabytes closer to the end. You will need to resize your media in order to achieve this.</p> <p><code>ffmpeg</code> (commandline) supports resizing videos: <a href="https://academy.cba.mit.edu/classes/computer_design/video.html">Neil's cheatsheet</a> is a good reference.</p> <p><code>ImageMagick</code> supports resizing images:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> convert <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">src_image</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>resize</span> 720x480 <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">dst_image</span></span></span> </span></code></pre> <h3 id="gitlab">GitLab?</h3> <p>I'm sure you've heard of GitHub; GitLab fills a similar niche. These are both git repo hosts with web frontends — they exist to be collaboration platforms. GitHub is a commercial project owned by Microsoft — GitLab is an open source protocol that can be self-hosted. This is what CBA does.</p> <h2 id="ui-clients">ui clients</h2> <ul> <li><a href="https://code.visualstudio.com/">VSCode</a> is the editor most of you are probably going to use — it has a git UI built in</li> <li><a href="https://desktop.github.com/download/">GitHub Desktop</a> is easy to use. You don't need to sign in with GitHub (you can skip that step), but based on my testing you will need to clone GitLab repos on the command line and add them manually</li> <li>GitLab web UI: this is a browser-embedded version of VS Code that lets you commit directly to GitLab. You <em>could</em> probably technically build your whole site this way, but there are some operations that will be easier locally.</li> </ul> <h2 id="why-what-is-version-control">why/what is version control?</h2> <p>Does this look familiar: <code>paper final final revised (Copy).docx</code>? In the language of version control, this document and its versions represent a linear edit history (read bottom-to-top for chronological order):</p> <pre class="z-code"><code><span class="z-text z-plain">* fix date (-&gt; paper final final revised (Copy).docx) </span><span class="z-text z-plain">| </span><span class="z-text z-plain">* more revisions (-&gt; paper final final revised.docx) </span><span class="z-text z-plain">| </span><span class="z-text z-plain">* grammar and spelling cleanup (-&gt; paper final final.docx) </span><span class="z-text z-plain">| </span><span class="z-text z-plain">* first round of edits, restructuring (-&gt; paper final.docx) </span><span class="z-text z-plain">| </span><span class="z-text z-plain">* first draft (-&gt; paper.docx) </span></code></pre> <p>Version control systems let you explicitly manage this history — rather than copying files manually for backup, you tell a VCS to record a new version of a file, and it records the change in the history for you. You can tell it to go to a different version, and it updates the file tree to look like it did at that version. There are many version control systems, but the one we use in this class (and the most popular for modern software development) is called <code>git</code>.</p> <h3 id="git-concepts">git concepts</h3> <p>Git operates at the scope of a directory. It stores the old versions of files and file history information in a "repository" (repo), which is just a directory on the filesystem. (Files aren't stored literally, there is a lot of cleverness in git to deduplicate and compress file versions.) To create a repo, run "git init":</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git init</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Initialized</span></span><span class="z-meta z-function-call z-arguments z-shell"> empty Git repository in <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">PWD</span></span>/.git/</span> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> This is telling you that git will store the data for the repo (version,</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> history data, etc.) in the `.git` directory.</span><span class="z-comment z-line z-number-sign z-shell"> </span></span></code></pre> <p>A "version" in git is called a "commit". When you record a new version of your files in git, you are "committing" them to the repo:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git add my_file</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git commit<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>m</span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>add my file<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[master</span></span><span class="z-meta z-function-call z-arguments z-shell"> 12a8bef] add my file <span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> 12a8bef is the commit id (hash)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span></span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">1</span></span><span class="z-meta z-function-call z-arguments z-shell"> file changed, 0 insertions(+</span><span class="z-meta z-function-call z-shell"></span>)<span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">,</span></span><span class="z-meta z-function-call z-arguments z-shell"> 0 deletions(-</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> new file, but it&#39;s empty</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">create</span></span><span class="z-meta z-function-call z-arguments z-shell"> mode 100644 my_file</span> </span></code></pre> <p>This is a two-step process:</p> <ul> <li>First tell git what you want to commit with <code>git add</code>. You can do this multiple times and omit files from being committed:</li> </ul> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> make a change to my_file</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> echo foo <span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> my_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> create two new files</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> echo bar <span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> another_file</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> echo qux <span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> ignored_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> tree</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-support z-function z-dot z-shell">.</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> my_file</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> another_file</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> ignored_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> only add another_file to be committed -- a `commit` right now will not</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> record ignored_file or changes to my_file!</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git add another_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> show files:</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> - that will be committed (&quot;staged&quot;)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> - that won&#39;t (&quot;not staged&quot;)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> - that git hasn&#39;t seen before (&quot;untracked&quot;)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git status</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">On</span></span><span class="z-meta z-function-call z-arguments z-shell"> branch master</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Changes</span></span><span class="z-meta z-function-call z-arguments z-shell"> to be committed:</span> </span><span class="z-source z-shell z-bash"> <span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">use</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>git restore --staged &lt;file&gt;...<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span> to unstage</span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">new</span></span><span class="z-meta z-function-call z-arguments z-shell"> file: another_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Changes</span></span><span class="z-meta z-function-call z-arguments z-shell"> not staged for commit:</span> </span><span class="z-source z-shell z-bash"> <span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">use</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>git add &lt;file&gt;...<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span> to update what will be committed</span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span> </span><span class="z-source z-shell z-bash"> <span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">use</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>git restore &lt;file&gt;...<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span> to discard changes in working directory</span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">modified:</span></span><span class="z-meta z-function-call z-arguments z-shell"> my_file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Untracked</span></span><span class="z-meta z-function-call z-arguments z-shell"> files:</span> </span><span class="z-source z-shell z-bash"> <span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">use</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>git add &lt;file&gt;...<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span> to include in what will be committed</span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ignored_file</span></span> </span></code></pre> <ul> <li>Then record the staged changes (those which have been <code>git add</code>ed) as a commit:</li> </ul> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git commit<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>m</span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>create another important file<span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[master</span></span><span class="z-meta z-function-call z-arguments z-shell"> 5552b2b] create another important file</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">1</span></span><span class="z-meta z-function-call z-arguments z-shell"> file changed, 1 insertions(+</span><span class="z-meta z-function-call z-shell"></span>)<span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">,</span></span><span class="z-meta z-function-call z-arguments z-shell"> 0 deletions(-</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">create</span></span><span class="z-meta z-function-call z-arguments z-shell"> mode 100644 another_file</span> </span></code></pre> <p>You can view the history with <code>git log</code>:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git log</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">commit</span></span><span class="z-meta z-function-call z-arguments z-shell"> 5552b2bebd5e185db2891ba2eb0fc91502e52780</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Author:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Nathan Perry <span class="z-keyword z-operator z-assignment z-redirection z-shell">&lt;</span>np@npry.dev<span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Date:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Mon Sep 9 14:10:23 2024<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>0400</span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">create</span></span><span class="z-meta z-function-call z-arguments z-shell"> another important file</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">commit</span></span><span class="z-meta z-function-call z-arguments z-shell"> 12a8befb21236ae527aa0cffbe59384b5493238b</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Author:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Nathan Perry <span class="z-keyword z-operator z-assignment z-redirection z-shell">&lt;</span>np@npry.dev<span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Date:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Mon Sep 9 13:52:23 2024<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>0400</span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">add</span></span><span class="z-meta z-function-call z-arguments z-shell"> my file</span> </span></code></pre> <p>I find this output is more readable with <code>git log --oneline</code>:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git log<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>oneline</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">5552b2bebd5e185db2891ba2eb0fc91502e52780</span></span><span class="z-meta z-function-call z-arguments z-shell"> create another important file</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">12a8befb21236ae527aa0cffbe59384b5493238b</span></span><span class="z-meta z-function-call z-arguments z-shell"> add my file</span> </span></code></pre> <h3 id="branching">branching</h3> <p>I mentioned in the first example that we were looking at a "linear" commit history. This is by contrast to a "branching" commit history. Git supports multiple concurrent versions of the repo, in separate "branches".</p> <p>A git branch is just a name that points to a commit. When you are "on" a branch, we call that having the branch "checked out". As you make commits, the branch updates to point to the most recent commit.</p> <p>You can switch branches with <code>git checkout $branch</code>, and you can create a branch with <code>git checkout -b $new_branch</code>. When you create a new branch this way, it starts out pointing to the commit you currently have checked out.</p> <h3 id="remotes">remotes</h3> <p>So far, the git we've described has been completely local — a way for you to store and browse the history of a project. Git also supports (indeed, is built for) collaboration with others. The most common way to accomplish this is by adding remote repositories:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> configure a remote called &quot;origin&quot; at the given address</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git remote add origin ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> print configured remotes</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git remote<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>v</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">origin</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span> (fetch</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">origin</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span> (push</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> &quot;push&quot; (send) your commits to the master branch on origin</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> associating (-u) the local master branch with the remote&#39;s</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git push<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>u</span> origin master</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> &quot;pull&quot; (receive) any new commits from the remote&#39;s master branch</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git pull origin master</span> </span></code></pre> <p><code>clone</code> downloads an existing remote repo and creates a local one based on it (with remote <code>origin</code> configured to point at the remote):</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> create a new git repo, configure origin with the given url,</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> and pull the default branch (main or master, depending)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git clone ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> cd <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span></span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> print configured remotes</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> git remote<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>v</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">origin</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span> (fetch</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">origin</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh://git@gitlab.cba.mit.edu:846/<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">YOUR_REPO</span></span> (push</span><span class="z-meta z-function-call z-shell"></span>) </span></code></pre> <p>Since your GitLab repos are already created, you should <code>clone</code> them.</p> 2024-08-27T00:00:00+00:00 2024-09-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/thesis/pitch/ <p>The project of pervasive computing and sensing is not succeeding. We imagined a future where the whole world is instrumented with cheap sensors and tiny computers — where data about the environment, machines, and humans is ubiquitous and easy to access; where these tiny computers can distribute work between them, in many cases obviating the need for dedicated computing devices.</p> <p>The reality we inhabit has made strides towards this vision but is far from attaining it. Components are inexpensive, firmware is open, and vendors provide cheap integrated solutions, yet in practice deploying a nontrivial networked embedded system requires substantial application-specific technical design and integration. The landscape of networked sensor systems remains one of bespoke, fragmented solutions and walled gardens — sensor instrumentation and compute embedding is routine in today's world but not commodity.</p> <p>In analogy to manufacturing, we live in a time before the adoption of standardized parts: the story of electronics hardware and firmware development is one of reinventing the wheel over and over again and hand-fitting each system to its particular application. This is not an existential challenge to the field — it is still possible to produce and deploy embedded electronics that provide paradigm-shifting capabilities — just as it was once possible for artisans to craft intricate and precise mechanisms with hand tooling alone. But it is drastically more difficult and costly to do so than the underlying technologies suggest it could be. Over-the-air updates, signaling schemes, networking protocols, message formats, bootloaders — anything that can be reinvented and respecialized will be — and I argue that this is an essential unsolved problem on the critical path to a future replete with readily-deployed, low-cost, networked embedded systems.</p> <p>A critical capability required for the broad deployment of these systems is transitive reachability across hetereogeneous node types through any variety of physical-layer interconnects (copper, radio, optical, etc.). If I can reach one node in the system, then I ought to be able to reach everything in the connected component of the network graph it belongs to. Further, this graph must be easy to extend — it can't require additional infrastructure to do so (hubs, access points, external servers, Internet access, etc.), except as physical reality dictates (range extension, signal conditioning due to distance or noise).</p> <p>To this end, I am building easily-integrated firmware libraries and hardware designs that enable the construction of hotpluggable, modular, switched or routed (L2/L3), densely connected ad-hoc networks of embedded devices over a variety of physical-layer interconnects (including SPI, UART, I2C, RS-232, Bluetooth) using standard Internet protocols. The primary technical contributions in this thesis are:</p> <ul> <li>Protocol specifications and drivers for each supported PHY</li> <li>Arduino-compatible firmware switch library enabling the aggregation of L2-compatible PHYs</li> <li>Arduino-compatible router library based on BATMAN, enabling hotpluggable ad-hoc network construction and modification</li> <li>Demonstrator systems showcasing communication between my own PCBs, a variety of Responsive Environments historical projects, and external network clients under variable network conditions</li> </ul> 2024-08-14T00:00:00+00:00 2024-08-14T00:00:00+00:00 Nathan Perry https://blog.npry.dev/clef/ <p><code>clef</code> started as a KiCad project template repo, but I just spent a day or two setting it up to support processing KiCad projects into 3d models, schematics, SVGs, and fabrication files through <a href="https://nixos.org">Nix</a>, which builds this blog. That means that as part of the deployment process for this blog, the version of the <a href="../resenv/ocularium">ocularium</a> repo that I've pinned is automatically built, meaning the content on that page is always up-to-date.</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> nix build .#</span> <span class="z-keyword z-operator z-logical z-and z-shell">&amp;&amp;</span> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">nix</span></span><span class="z-meta z-function-call z-arguments z-shell"> run nixpkgs#tree result</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">result</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> share</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> npry</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> ocularium</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> fab</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── bom.csv</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── gerbers.zip</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> └── pos.csv</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> model</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── okm.glb</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> └── okm.step</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> schematic</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── schematic.pdf</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> └── svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── IO.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── MCU.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── Power.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> ├── root.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">│</span></span><span class="z-meta z-function-call z-arguments z-shell"> └── Sensors.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> back.mirror.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> back.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> front.mirror.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> front.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> in1.mirror.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> in1.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">├──</span></span><span class="z-meta z-function-call z-arguments z-shell"> in2.mirror.svg</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">└──</span></span><span class="z-meta z-function-call z-arguments z-shell"> in2.svg</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">8</span></span><span class="z-meta z-function-call z-arguments z-shell"> directories, 19 files</span> </span></code></pre> <h2 id="board-svgs">board svgs</h2> <p>I've just realized the board SVGs exported by KiCad are <em>actual size</em> (they embed board dimensions), so when rendered on a webpage they are by default the real size of the board. I added an inkscape step to <code>.svgs</code> to support trimming off the substantial whitespace KiCad includes so they're easier to embed (inkscape preserves the size metadata, including adjusting for its trimmed size).</p> 2024-08-12T00:00:00+00:00 2024-08-12T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/oneclick-jlc/ <p>In pursuit of more and better open source hardware, I'd really love it if JLC, PCBWay, or <code>$FAVORITE_CHEAP_FAST_BOARD_HOUSE</code> exposed the ability to manage a whole board package (gerbers, board stackup + assembly configuration, BoM, selected parts, placement) as a semantic object through their API. I'd like to be able to:</p> <ul> <li>click a button and deterministically populate an order package</li> <li>query the API for what an order package will cost</li> <li>query the API for what parts in an order package aren't available</li> </ul> <p>The historical status quo was that only engineers understood how to get a board fabbed. Now dedicated hobbyists can do this, and it's only getting easier. I think there's a huge market to capture here, and there will be someone who gets it first — the board houses can cut out the middlemen without much risk simply by reducing the friction in ordering PCBs. In the meantime I'm frustrated that I have to keep clicking through the JLC web UI every time I want to change my order and <a href="https://jlcpcb.com/help/article/jlcpcb-online-api-available-now">it's not possible to automate (last update 11/2023)</a>:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;api_suspended.9fc31191d6830734.jpg"> </div> 2024-08-11T00:00:00+00:00 2024-08-11T00:00:00+00:00 Nathan Perry https://blog.npry.dev/ppq/ <p>It is a pain in the ass to get project images from my phone (camera) to my documentation, and then it's frequently an additional manual step to resize, and then I have to go back and delete them off the phone, as I wasn't trying to preserve the images in Google Photos/iCloud in the first place--version control on the documentation is responsible for that persistence. First world problems, sure, but it's a bunch of additional friction to adding images ("documenting as you go"), which demonstrably makes documentation more engaging and clear.</p> <p>A 60% solution is <a href="https://github.com/magic-wormhole/magic-wormhole">magic wormhole</a> on the receiving device with something like <a href="https://play.google.com/store/apps/details?id=io.sanford.wormhole_william&amp;hl=en_US">wormhole william</a> on the phone. That lets me document as I go, but I need the wormhole running all the time, I need to sync the code, and I need to take the images out-of-band. Basically I need my laptop with me and set up to synchronously receive everything. That's fine, but I often am taking pictures in-the-moment, and it's not guaranteed everything will be set up this way ahead of time.</p> <p>What I actually want is a client-side partitioned media queue that doesn't require a concurrent receiving device — open the app, make a queue, take a bunch of pictures, go back and title ones I want to keep, they automatically upload. Later, when I'm writing up the docs, run something like:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> cd blog/content/current-post</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ppq list</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">htm</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>5 pending<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ppq dump<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>q</span> htm<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>resize</span> 720x480</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">dequeue</span></span><span class="z-meta z-function-call z-arguments z-shell"> demo1.jpg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">dequeue</span></span><span class="z-meta z-function-call z-arguments z-shell"> demo2.jpg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">dequeue</span></span><span class="z-meta z-function-call z-arguments z-shell"> demo.mp4</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">dequeue</span></span><span class="z-meta z-function-call z-arguments z-shell"> test.jpg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">dequeue</span></span><span class="z-meta z-function-call z-arguments z-shell"> broken.jpg</span> </span></code></pre> <p>I'd also like to support:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ppq stream<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>q</span> htm<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>resize</span> 720x480</span> </span></code></pre> <p>to stream all the files as I take them, and possibly some undo functionality.</p> <h2 id="language-choices">language choices</h2> <p>I'll probably write the server component in Elixir, as I've been playing with it recently and this really is a distributed systems problem. I could just use NATS + JetStream, but I kinda don't want to deal with its authentication system / overload it here.</p> <p>Phone app is Kotlin on Android unless there's something nice for Rust (seems like <a href="https://github.com/rust-mobile/android-activity">maybe</a> — might try it out if it doesn't seem like too much of a pain in the ass).</p> <p>CLI will be Rust.</p> <h2 id="design-sketch">design sketch</h2> <h3 id="server">server</h3> <p>Relational DB (probably just SQLite? I don't think PG is worth it) for queues + Phoenix for REST API.</p> <ul> <li> <p><code>GET /</code>: list all queues</p> </li> <li> <p><code>POST /:name</code>: create queue</p> </li> <li> <p><code>DELETE /:name</code>: delete queue</p> </li> <li> <p><code>GET /:name</code>: list items in queue (metadata only)</p> </li> <li> <p><code>POST /:name/item</code>: add item, returns uuid</p> </li> <li> <p><code>DELETE /:name/:uuid</code>: remove item</p> </li> <li> <p><code>POST /:name/dump</code>: download and remove all items in queue</p> </li> </ul> <h3 id="phone-app">phone app</h3> <ul> <li>Login activity -- set server, token (JWT)</li> <li>Home activity: queue list (names, number of items)</li> <li>Queue detail activity: image grid + detail edit modal</li> </ul> <h3 id="cli">cli</h3> <ul> <li> <p><code>configure --server $server --token $token</code></p> </li> <li> <p><code>list</code> -&gt; <code>GET /</code></p> </li> <li> <p><code>-q $name create</code> -&gt; <code>POST /:name</code></p> </li> <li> <p><code>-q $name rm</code> -&gt; <code>DELETE /:name</code></p> </li> <li> <p><code>-q $name list</code> -&gt; <code>GET /:name</code></p> </li> <li> <p><code>-q $name post &lt; $item</code> -&gt; <code>POST /:name/item</code></p> </li> <li> <p><code>-q $name rm $uuid</code> -&gt; <code>DELETE /:name/:uuid</code></p> </li> <li> <p><code>-q $name dump</code> -&gt; <code>POST /:name/dump</code>SERVER</p> </li> </ul> 2024-08-11T00:00:00+00:00 2024-08-27T00:00:00+00:00 Nathan Perry https://blog.npry.dev/tinysearch/ <p><a href="https://github.com/tinysearch/tinysearch">tinysearch</a> is a static site-embedded search engine written in Rust by <a href="https://endler.dev">Matthias Endler</a>. It consumes a <a href="https://www.fusejs.io/">fuse</a> index (in my case, <a href="https://www.getzola.org/documentation/content/search/">generated by Zola</a>) and emits a WASM binary containing the index and search engine that can be loaded by the site and hooked up to an input element (see the search bar above).</p> <p>The functionality is great, but it's incompatible with <a href="https://nixos.org/"><code>nix</code></a> in its current state, as the tinysearch generator requires network access. In particular, it:</p> <ul> <li>generates a <code>storage</code> blob in its preferred format from the Zola-emitted search index</li> <li>generates an "engine" crate containing the search logic, which also embeds the <code>storage</code> blob</li> <li>calls <a href="https://github.com/rustwasm/wasm-pack"><code>wasm-pack</code></a> to build the engine crate <ul> <li>which calls <a href="https://github.com/rustwasm/wasm-bindgen"><code>wasm-bindgen</code></a> <ul> <li><strong>which shells out to <code>cargo</code></strong></li> </ul> </li> </ul> </li> <li>calls <a href="https://github.com/WebAssembly/binaryen"><code>wasm-opt</code></a> on the result (optionally) to reduce size</li> </ul> <p>The bolded step requires network access because <code>cargo build</code> has to download dependencies. Nix tooling normally solves for this by vendoring dependencies using the crate's <code>Cargo.lock</code> and then invoking <code>cargo build --offline</code>, but it's not possible to configure this through the <code>tinysearch</code> -&gt; <code>wasm-pack</code> -&gt; <code>wasm-bindgen</code> stack.</p> <h2 id="nix-port">nix port</h2> <p>I ported <code>tinysearch</code> support to Nix in a pair of packages:</p> <ul> <li><code>tinysearch</code>: search index generator — consumes a fuse index, outputs a <code>storage</code> blob (runs on the host, ported using <a href="https://crane.dev/">crane</a>)</li> </ul> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> produces tinysearch index at ./store</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> tinysearch<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>m</span> store search_index.en.json</span> </span></code></pre> <ul> <li><code>tinysearch_engine</code>: wasm payload and js wrapper to be loaded by website <ul> <li>Base <code>wasm</code> payload built directly through <code>cargo build --target wasm32-unknown-unknown</code>, via crane</li> <li>Invoke <code>wasm_bindgen --target web</code> on the result to produce the js wrapper</li> <li>Invoke <code>wasm-opt</code> on that result to minimize wasm payload size</li> </ul> </li> </ul> <p>I include it in my blog build like this:</p> <pre data-lang="nix" class="language-nix z-code"><code class="language-nix" data-lang="nix"><span class="z-source z-nix"><span class="z-comment z-line z-number-sign z-nix"># flake.nix -- details elided for concision</span> </span><span class="z-source z-nix"><span class="z-punctuation z-definition z-attrset-or-function z-nix">{</span> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">inputs</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-punctuation z-definition z-attrset-or-function z-nix">{</span> </span><span class="z-source z-nix"> <span class="z-comment z-line z-number-sign z-nix"># ...</span> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">tinysearch_nix</span>.<span class="z-entity z-other z-attribute-name z-multipart z-nix">url</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-string z-quoted z-double z-nix"><span class="z-punctuation z-definition z-string z-double z-start z-nix">&quot;</span>git+https://pub.npry.dev/tinysearch_nix<span class="z-punctuation z-definition z-string z-double z-end z-nix">&quot;</span></span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"> <span class="z-punctuation z-definition z-attrset z-nix">}</span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">outputs</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-punctuation z-definition z-entity z-function z-2 z-nix">{</span> <span class="z-variable z-parameter z-function z-1 z-nix">flake-utils</span><span class="z-keyword z-operator z-nix">,</span> <span class="z-keyword z-operator z-nix">... </span><span class="z-punctuation z-definition z-entity z-function z-nix">}</span> @ <span class="z-variable z-parameter z-function z-3 z-nix">inputs</span><span class="z-punctuation z-definition z-function z-nix">:</span> <span class="z-punctuation z-definition z-expression z-nix">(</span><span class="z-variable z-parameter z-name z-nix">flake-utils</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">lib</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">eachDefaultSystem</span> <span class="z-punctuation z-definition z-expression z-nix">(</span><span class="z-variable z-parameter z-function z-4 z-nix">system</span><span class="z-punctuation z-definition z-function z-nix">:</span> <span class="z-keyword z-other z-nix">let</span> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">pkgs</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-support z-function z-nix">import</span> <span class="z-variable z-parameter z-name z-nix">nixpkgs</span> <span class="z-punctuation z-definition z-attrset-or-function z-nix">{</span> </span><span class="z-source z-nix"> <span class="z-keyword z-other z-inherit z-nix">inherit</span> <span class="z-entity z-other z-attribute-name z-single z-nix">system</span><span class="z-punctuation z-terminator z-inherit z-nix">;</span> </span><span class="z-source z-nix"> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">overlays</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-punctuation z-definition z-list z-nix">[</span> </span><span class="z-source z-nix"> <span class="z-variable z-parameter z-name z-nix">inputs</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">tinysearch_nix</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">overlays</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">default</span> </span><span class="z-source z-nix"> <span class="z-punctuation z-definition z-list z-nix">]</span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"> <span class="z-punctuation z-definition z-attrset z-nix">}</span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"> </span><span class="z-source z-nix"> <span class="z-keyword z-other z-nix">in</span> <span class="z-punctuation z-definition z-attrset-or-function z-nix">{</span> </span><span class="z-source z-nix"> <span class="z-entity z-other z-attribute-name z-multipart z-nix">packages</span>.<span class="z-entity z-other z-attribute-name z-multipart z-nix">default</span> <span class="z-keyword z-operator z-bind z-nix">=</span> <span class="z-variable z-parameter z-name z-nix">pkgs</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">callPackage</span> <span class="z-string z-unquoted z-path z-nix">./blog.nix</span> <span class="z-punctuation z-definition z-attrset z-nix">{</span><span class="z-punctuation z-definition z-attrset z-nix">}</span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"> <span class="z-punctuation z-definition z-attrset z-nix">}</span><span class="z-punctuation z-definition z-expression z-nix">)</span><span class="z-punctuation z-definition z-expression z-nix">)</span><span class="z-punctuation z-terminator z-bind z-nix">;</span> </span><span class="z-source z-nix"><span class="z-punctuation z-definition z-attrset z-nix">}</span> </span></code></pre> <pre data-lang="nix" class="language-nix z-code"><code class="language-nix" data-lang="nix"><span class="z-source z-nix"><span class="z-comment z-line z-number-sign z-nix"># blog.nix</span> </span><span class="z-source z-nix"><span class="z-punctuation z-definition z-attrset-or-function z-nix">{</span> </span><span class="z-source z-nix"> <span class="z-comment z-line z-number-sign z-nix"># ...</span> </span><span class="z-source z-nix"> <span class="z-variable z-parameter z-function z-1 z-nix">runCommand</span><span class="z-keyword z-operator z-nix">,</span> </span><span class="z-source z-nix"> </span><span class="z-source z-nix"> <span class="z-variable z-parameter z-function z-1 z-nix">tinysearch</span><span class="z-keyword z-operator z-nix">,</span> </span><span class="z-source z-nix"> <span class="z-variable z-parameter z-function z-1 z-nix">tinysearch_engine</span><span class="z-keyword z-operator z-nix">,</span> </span><span class="z-source z-nix"><span class="z-punctuation z-definition z-entity z-function z-nix">}</span><span class="z-punctuation z-definition z-function z-nix">:</span> <span class="z-variable z-parameter z-name z-nix">runCommand</span> <span class="z-string z-quoted z-double z-nix"><span class="z-punctuation z-definition z-string z-double z-start z-nix">&quot;</span>my_blog<span class="z-punctuation z-definition z-string z-double z-end z-nix">&quot;</span></span> <span class="z-punctuation z-definition z-attrset z-nix">{</span><span class="z-punctuation z-definition z-attrset z-nix">}</span> <span class="z-string z-quoted z-other z-nix"><span class="z-punctuation z-definition z-string z-other z-start z-nix">&#39;&#39;</span> </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> # blog build elided </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> blog_generate_index | \ </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> <span class="z-markup z-italic"><span class="z-punctuation z-section z-embedded z-begin z-nix">${</span><span class="z-variable z-parameter z-name z-nix">tinysearch</span><span class="z-keyword z-operator z-nix">.</span><span class="z-variable z-parameter z-name z-nix">generate_index</span><span class="z-punctuation z-section z-embedded z-end z-nix">}</span></span>/bin/tinysearch_generate_index &gt; $out/tinysearch_index </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> cp <span class="z-markup z-italic"><span class="z-punctuation z-section z-embedded z-begin z-nix">${</span><span class="z-variable z-parameter z-name z-nix">tinysearch_engine</span><span class="z-punctuation z-section z-embedded z-end z-nix">}</span></span> $out/tinysearch_engine </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"> cp <span class="z-markup z-italic"><span class="z-punctuation z-section z-embedded z-begin z-nix">${</span><span class="z-string z-unquoted z-path z-nix">./search.js</span><span class="z-punctuation z-section z-embedded z-end z-nix">}</span></span> $out/search.js </span></span><span class="z-source z-nix"><span class="z-string z-quoted z-other z-nix"><span class="z-punctuation z-definition z-string z-other z-end z-nix">&#39;&#39;</span></span> </span></code></pre> <h3 id="engine-changes">engine changes</h3> <p>I changed <code>tinysearch_engine</code> to not embed the search index; rather, the wasm blob is now <em>just</em> the search engine, and you dynamically load (possibly multiple) indices into it before using it. The result is less "batteries included" and requires another roundtrip to the server, but is more straightforwardly compatible with the Nix build process.<sup class="footnote-reference"><a href="#1">1</a></sup></p> <p>Before:</p> <pre data-lang="js" class="language-js z-code"><code class="language-js" data-lang="js"><span class="z-source z-ts"><span class="z-meta z-import z-ts"><span class="z-keyword z-control z-import z-ts">import</span> <span class="z-meta z-block z-ts"><span class="z-punctuation z-definition z-block z-ts">{</span> <span class="z-variable z-other z-readwrite z-alias z-ts">search</span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-keyword z-control z-default z-ts">default</span> <span class="z-keyword z-control z-as z-ts">as</span> <span class="z-variable z-other z-readwrite z-alias z-ts">init</span> <span class="z-punctuation z-definition z-block z-ts">}</span></span> <span class="z-keyword z-control z-from z-ts">from</span> <span class="z-string z-quoted z-single z-ts"><span class="z-punctuation z-definition z-string z-begin z-ts">&#39;</span>tinysearch<span class="z-punctuation z-definition z-string z-end z-ts">&#39;</span></span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Init tinysearch engine.</span> </span><span class="z-source z-ts"><span class="z-keyword z-control z-flow z-ts">await</span> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">init</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-meta z-brace z-round z-ts">)</span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Submit a user query.</span> </span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">results</span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">search</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-string z-quoted z-single z-ts"><span class="z-punctuation z-definition z-string z-begin z-ts">&#39;</span>user_search<span class="z-punctuation z-definition z-string z-end z-ts">&#39;</span></span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-constant z-numeric z-decimal z-ts">5</span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span></code></pre> <p>After:</p> <pre data-lang="js" class="language-js z-code"><code class="language-js" data-lang="js"><span class="z-source z-ts"><span class="z-meta z-import z-ts"><span class="z-keyword z-control z-import z-ts">import</span> <span class="z-meta z-block z-ts"><span class="z-punctuation z-definition z-block z-ts">{</span> <span class="z-variable z-other z-readwrite z-alias z-ts">search</span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-variable z-other z-readwrite z-alias z-ts">load_filters</span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-keyword z-control z-default z-ts">default</span> <span class="z-keyword z-control z-as z-ts">as</span> <span class="z-variable z-other z-readwrite z-alias z-ts">init</span> <span class="z-punctuation z-definition z-block z-ts">}</span></span> <span class="z-keyword z-control z-from z-ts">from</span> <span class="z-string z-quoted z-single z-ts"><span class="z-punctuation z-definition z-string z-begin z-ts">&#39;</span>tinysearch<span class="z-punctuation z-definition z-string z-end z-ts">&#39;</span></span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts"><span class="z-entity z-name z-function z-ts">fetch_index</span></span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-meta z-arrow z-ts"><span class="z-storage z-modifier z-async z-ts">async</span> <span class="z-meta z-parameters z-ts"><span class="z-punctuation z-definition z-parameters z-begin z-ts">(</span><span class="z-variable z-parameter z-ts">index_path</span><span class="z-punctuation z-definition z-parameters z-end z-ts">)</span></span> </span><span class="z-meta z-arrow z-ts"><span class="z-storage z-type z-function z-arrow z-ts">=&gt;</span> <span class="z-meta z-block z-ts"><span class="z-punctuation z-definition z-block z-ts">{</span> </span></span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-arrow z-ts"><span class="z-meta z-block z-ts"> <span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">resp</span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-keyword z-control z-flow z-ts">await</span> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">fetch</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-variable z-other z-readwrite z-ts">index_path</span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span></span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-arrow z-ts"><span class="z-meta z-block z-ts"> <span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">blob</span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-keyword z-control z-flow z-ts">await</span> <span class="z-meta z-function-call z-ts"><span class="z-variable z-other z-object z-ts">resp</span><span class="z-punctuation z-accessor z-ts">.</span><span class="z-entity z-name z-function z-ts">blob</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span></span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-arrow z-ts"><span class="z-meta z-block z-ts"> <span class="z-keyword z-control z-flow z-ts">return</span> <span class="z-keyword z-control z-flow z-ts">await</span> <span class="z-meta z-function-call z-ts"><span class="z-variable z-other z-object z-ts">blob</span><span class="z-punctuation z-accessor z-ts">.</span><span class="z-entity z-name z-function z-ts">bytes</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-meta z-brace z-round z-ts">)</span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span></span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-arrow z-ts"><span class="z-meta z-block z-ts"><span class="z-punctuation z-definition z-block z-ts">}</span></span></span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-array-binding-pattern-variable z-ts"><span class="z-punctuation z-definition z-binding-pattern z-array z-ts">[</span><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">_</span></span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">index_store</span></span><span class="z-punctuation z-definition z-binding-pattern z-array z-ts">]</span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-keyword z-control z-flow z-ts">await</span> <span class="z-meta z-function-call z-ts"><span class="z-support z-class z-promise z-ts">Promise</span><span class="z-punctuation z-accessor z-ts">.</span><span class="z-support z-function z-promise z-ts">all</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-meta z-array z-literal z-ts"><span class="z-meta z-brace z-square z-ts">[</span> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"><span class="z-punctuation z-whitespace z-comment z-leading z-ts"> </span><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Init tinysearch engine.</span> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">init</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-meta z-brace z-round z-ts">)</span><span class="z-punctuation z-separator z-comma z-ts">,</span> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"><span class="z-punctuation z-whitespace z-comment z-leading z-ts"> </span><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Fetch the search index from the backend.</span> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">fetch_index</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-string z-quoted z-single z-ts"><span class="z-punctuation z-definition z-string z-begin z-ts">&#39;</span>/tinysearch_index<span class="z-punctuation z-definition z-string z-end z-ts">&#39;</span></span><span class="z-meta z-brace z-round z-ts">)</span><span class="z-punctuation z-separator z-comma z-ts">,</span> </span></span></span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-meta z-array z-literal z-ts"><span class="z-meta z-brace z-square z-ts">]</span></span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Load the index into tinysearch.</span> </span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">filters</span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">load_filters</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-variable z-other z-readwrite z-ts">index_store</span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span><span class="z-source z-ts"> </span><span class="z-source z-ts"><span class="z-comment z-line z-double-slash z-ts"><span class="z-punctuation z-definition z-comment z-ts">//</span></span><span class="z-comment z-line z-double-slash z-ts"> Submit a user query.</span> </span><span class="z-source z-ts"><span class="z-meta z-var z-expr z-ts"><span class="z-storage z-type z-ts">const</span> <span class="z-meta z-var-single-variable z-expr z-ts"><span class="z-meta z-definition z-variable z-ts"><span class="z-variable z-other z-constant z-ts">results</span></span> </span><span class="z-keyword z-operator z-assignment z-ts">=</span> <span class="z-meta z-function-call z-ts"><span class="z-entity z-name z-function z-ts">search</span></span><span class="z-meta z-brace z-round z-ts">(</span><span class="z-variable z-other z-readwrite z-ts">filters</span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-string z-quoted z-single z-ts"><span class="z-punctuation z-definition z-string z-begin z-ts">&#39;</span>user_search<span class="z-punctuation z-definition z-string z-end z-ts">&#39;</span></span><span class="z-punctuation z-separator z-comma z-ts">,</span> <span class="z-constant z-numeric z-decimal z-ts">5</span><span class="z-meta z-brace z-round z-ts">)</span></span><span class="z-punctuation z-terminator z-statement z-ts">;</span> </span></code></pre> <div class="footnote-definition" id="1"><sup class="footnote-definition-label">1</sup> <p>And technically more flexible, in that you can load the engine and index separately — e.g. per-user site indices, dynamically updating the active index with up-to-date information, or loading multiple indices for distinct search domains.</p> </div> 2024-08-09T00:00:00+00:00 2024-08-10T00:00:00+00:00 Nathan Perry https://blog.npry.dev/git-repo-frontends/ <p>Maybe I'm unduly accustomed to the github UI, but to me the singularly useful way to view a git repo is a unified file tree + readme page. It's unfortunate that there appear to be no standalone web frontends that do this.</p> <h2 id="motivation">motivation</h2> <p>When I'm glancing at a git repo, I want:</p> <ul> <li>basic documentation</li> <li>access to files in the repo</li> <li>ability to change branch / tag</li> </ul> <h2 id="availability">availability</h2> <p>Plenty of git <em>hosting</em> tools provide this experience all in one place — github, <a href="https://gitea.com">gitea</a>/<a href="https://gogs.io">gogs</a>, and now gitlab<sup class="footnote-reference"><a href="#1">1</a></sup> to my knowledge have the tree-and-readme page figured out — but I can't find any standalone git web frontends that do the same.</p> <ul> <li><a href="https://git-scm.com/book/en/v2/Git-on-the-Server-GitWeb">gitweb</a> shows a commit shortlog as the summary, and the tree page doesn't render readmes.</li> <li><a href="https://git.zx2c4.com/cgit/about/">cgit</a> (which I'm currently using) has separate "about" (rendered readme) and tree pages. I also want to dump C if possible.</li> <li><a href="https://sr.ht">sourcehut</a> (hosting service) separates the rendered readme and tree.</li> <li><a href="https://git.icyphox.sh">legit</a> separates the rendered readme and tree.</li> <li><a href="https://narkoz.github.io/ginatra">ginatra</a> appears not have readme and tree on the main repo summary page, based on screenshots. Unclear if they're rendered together. Not usually willing to run Ruby anyway.</li> <li><a href="https://bitubucket.org">bitbucket</a> (hosting service) is owned by Atlassian.</li> <li><a href="https://klausdemo.lophus.org">klaus</a> has the features I want, but 500ed several times as I was browsing the demo site (and is ugly, imo).</li> </ul> <p>I will probably fork one of these projects or write my own when I'm procrastinating sometime soon, but I'm honestly shocked there isn't something that exists for me.</p> <h2 id="why-do-i-care">why do i care</h2> <p>Gitea hosts all of my personal source code, but I don't want to use it as the frontend for <a href="https://pub.npry.dev">https://pub.npry.dev</a> — my public source code is a read-only set of HTTP-accessible git repos, and I intend for it to stay that way.</p> <div class="footnote-definition" id="1"><sup class="footnote-definition-label">1</sup> <p>I believe this wasn't the case until quite recently.</p> </div> 2024-08-09T00:00:00+00:00 2024-08-09T00:00:00+00:00 Nathan Perry https://blog.npry.dev/rdap/ <p>As part of a long train of dependencies and distractions involved in setting the CORS headers for <a href="../resenv/ocularium">ocularium</a>'s <a href="https://pub.npry.dev/ocularium/tree">schematics</a>, I discovered a number of web crawlers accessing pages my robots.txt told them not to, so I decided to IP blacklist them in my reverse proxy.</p> <h2 id="tcpdump-wireshark">tcpdump -&gt; wireshark</h2> <p>I don't generally leave http access logs on, and I figured there was probably a less-invasive and -stateful way to capture the source IPs I as interested in than updating my nginx config. I went with this <code>tcpdump</code> invocation initially, inspecting HTTP traffic behind my TLS termination with <code>wireshark</code>, looking for <code>X-Forwarded-For</code>:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">REMOTE_SYSTEM</span></span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>tcpdump -s 0 -U -n -w - -i <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">IFACE</span></span><span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span> <span class="z-keyword z-operator z-assignment z-redirection z-shell">&gt;</span> out.pcap</span> <span class="z-keyword z-operator z-logical z-and z-shell">&amp;&amp;</span> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">wireshark</span></span> </span></code></pre> <p>This became time-consuming as there were a lot of subnets to block, all coming from Huawei Cloud (Singapore) IPs, and I had to rerun, analyze the capture, and add to my blacklist in repeated batches.</p> <h2 id="tshark">tshark</h2> <p>Once I had enough of this manual process I found <code>tshark</code>, a commandline interface to wireshark's functionality, and was able to stream WHOIS results:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ssh <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">REMOTE_SYSTEM</span></span> <span class="z-string z-quoted z-double z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&quot;</span>tcpdump -s 0 -U -n -w - -i <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">IFACE</span></span><span class="z-punctuation z-definition z-string z-end z-shell">&quot;</span></span></span> <span class="z-keyword z-operator z-logical z-pipe z-shell">|</span> <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">tshark</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>i</span> -<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>Y</span> <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>http.request.uri.path contains &quot;/interesting&quot; &amp;&amp; http.x_forwarded_for<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span> <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>T</span> fields<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>e</span> <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>http.x_forwarded_for<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span></span> <span class="z-keyword z-operator z-logical z-pipe z-shell">|</span> <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">xargs</span></span><span class="z-meta z-function-call z-arguments z-shell"><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>n1</span> whois</span> <span class="z-keyword z-operator z-logical z-pipe z-shell">|</span> <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">egrep</span></span><span class="z-meta z-function-call z-arguments z-shell"><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>i</span> <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>route|CIDR|Organization|Country|netname<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>line-buffered</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Country:</span></span><span class="z-meta z-function-call z-arguments z-shell"> SG</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">route:</span></span><span class="z-meta z-function-call z-arguments z-shell"> 94.74.80.0/20</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Country:</span></span><span class="z-meta z-function-call z-arguments z-shell"> ZZ</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Country:</span></span><span class="z-meta z-function-call z-arguments z-shell"> SG</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">netname:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Huawei-Cloud-SG</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">...</span></span> </span></code></pre> <p>This hacked approach worked but gave pretty ugly and imprecise results, and by this point I figured I was seeing enough volume consistently that it was worth going the whole nine yards and packaging it up into a systemd service whose logs I can grep at my leisure.</p> <h2 id="full-automation">full automation</h2> <p>First, <code>tshark</code> can take over <code>tcpdump</code>'s responsibilities:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> tshark<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>i</span> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">IFACE</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>Y</span> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">FILTER</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>T</span> fields<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>e</span> <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>http.x_forwarded_for<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>l</span></span> </span></code></pre> <p>And then to make the results nicer than the whois -&gt; grep from above, so it'd be easy to read and the association ip -&gt; owner, it turns out <a href="https://about.rdap.org/">RDAP</a> is the new iteration of WHOIS — basically the same info, just in a REST JSON API — and there are plenty of free services out there. I came across <a href="https://www.ripe.net/">RIPE</a> first and wrote a quick Python script that reads IPs off of stdin and logs <code>(IP, CIDR, owner, country)</code> with a Bash script to feed it:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell">!/usr/bin/env bash</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-support z-function z-set z-shell">set</span></span><span class="z-meta z-function-call z-arguments z-shell"> -euo pipefail</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">tshark</span></span><span class="z-meta z-function-call z-arguments z-shell"><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>i</span> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">IFACE</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>Y</span> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">FILTER</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>T</span> fields<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>e</span> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">EXPR</span></span><span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>l</span></span> <span class="z-keyword z-operator z-logical z-pipe z-shell">|</span> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">rdap</span></span> </span></code></pre> <p>And a systemd service unit, expressed as a <a href="https://nixos.org">NixOS</a> module.</p> <p>Results of the first few hours (I had already blocked the worst-offending subnets -- this is comparatively slow):</p> <pre class="z-code"><code><span class="z-text z-plain">22:20:59 cidrs=[&#39;94.74.80.0/20&#39;] country=SG ip=94.74.93.108 name=Huawei-Cloud-SG </span><span class="z-text z-plain">22:22:28 cidrs=[&#39;114.119.172.0/22&#39;] country=SG ip=114.119.174.108 name=Huawei-Cloud-Singapore </span><span class="z-text z-plain">22:24:14 cidrs=[&#39;166.108.192.0/19&#39;] country=SG ip=166.108.201.248 name=Huawei-Cloud-SG </span><span class="z-text z-plain">23:43:56 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">00:11:57 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">00:17:50 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">00:38:07 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.88.165 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">01:39:10 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">02:02:30 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span><span class="z-text z-plain">02:42:54 cidrs=[&#39;159.138.80.0/20&#39;] country=SG ip=159.138.85.139 name=Huawei-SG-CLOUDS </span></code></pre> <p>I plan to publish the scripts and NixOS module sooner or later.</p> <h2 id="postscript-robots-txt">postscript: <code>robots.txt</code></h2> <p>As it turns out, I had originally misconfigured nginx and only had <code>robots.txt</code> for the default http vhost, meaning none of the crawlers I was looking at ever saw it -- amazonbot probably wasn't being impolite.</p> 2024-08-08T00:00:00+00:00 2024-09-25T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/ocularium/ <link rel="stylesheet" href="ocularium.css"/> <script async type="module" src="https://ajax.googleapis.com/ajax/libs/model-viewer/3.5.0/model-viewer.min.js"></script> <script async type="module" src="board_zoom.js"></script> <script async type="module" src="annotations.js"></script> <p><em>Board renders, schematics, interactive bom, and fabrication files on this page were automatically generated by <a href="../../clef">clef</a> + <a href="https://nixos.org">Nix</a>.</em></p> <p><a href="/ocularium/bom/ibom.html">interactive bom</a></p> <div id="model_parent"> <model-viewer src="/ocularium/model/okm.glb" shadow-intensity="1" camera-controls touch-action="pan-y" environment-image="https://modelviewer.dev/shared-assets/environments/music_hall_01_1k.hdr"> <noscript> <p>JavaScript disabled, model viewer not loaded.</p> <a href="/ocularium/model/okm.glb">Download board model (.glb)</a> </noscript> <button class="Hotspot" slot="hotspot-1" data-position="0.14760093670821386m 0.0026000000160187487m 0.09963027191667925m" data-normal="0m 1m 0m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">rp2040 (microcontroller)</div> </button><button class="Hotspot" slot="hotspot-2" data-position="0.13439221206217564m 0.004166923014032854m 0.10490555174254299m" data-normal="0m 1m 0m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">veml7700 (lux)</div> </button><button class="Hotspot" slot="hotspot-3" data-position="0.14069545004446807m -0.002050000094994888m 0.10398218950734957m" data-normal="4.4408920985006257e-16m -1m -9.860761315262644e-32m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">micro SD</div> </button><button class="Hotspot" slot="hotspot-4" data-position="0.1599382733020378m -0.0033099999103695177m 0.10126869139545787m" data-normal="-4.440892098500625e-16m -1m -9.860761315262643e-32m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">usb-c (charging)</div> </button><button class="Hotspot" slot="hotspot-5" data-position="0.14117298271012144m 0.0026300000116229196m 0.08929344628723895m" data-normal="-3.9518573113016147e-32m 1m 2.2204460492503136e-16m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">microphone</div> </button><button class="Hotspot" slot="hotspot-6" data-position="0.15221604145787268m -0.0008300000021234221m 0.1035482132730995m" data-normal="-1.2246467991473532e-16m -1m 3.951857311301614e-32m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">accel &amp; gyro</div> </button><button class="Hotspot" slot="hotspot-7" data-position="0.14205263746719196m 0.002430000002123416m 0.10618781385778686m" data-normal="0m 1m 0m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">bme680 (gas)</div> </button> <button class="Hotspot" slot="hotspot-8" data-position="0.14436974369641598m 0.0037681753294515974m 0.11432977456046267m" data-normal="0.9975640484642385m 0.06975649942219526m 1.3765541624477502e-16m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">debug</div> </button> <button class="Hotspot" slot="hotspot-9" data-position="0.15372688248764602m 0.0031500000130385165m 0.11273835360211604m" data-normal="0m 1m 0m" data-visibility-attribute="visible"> <div class="HotspotAnnotation">battery</div> </button> </model-viewer> <div id="annotations"> <input type="checkbox" unchecked> <label>annotations</label> </div> </div> <p><em>ocularium</em> is a tiny sensor platform I designed to be flown on kites. I'm working with <a href="https://chuchoocampo.com">Chucho Ocampo</a> on this project, who I met on <a href="https://www.media.mit.edu/projects/lunar-research-in-lanzarote/overview/">SEI's trip to Lanzarote</a>.</p> <div class="board_outer"> <div class="board_inner"> <div class="board_wrap"> <img src="/ocularium/svg/front.trim.svg" class="boardimg noborder"/> <i>front</i> </div> <div class="board_wrap"> <img src="/ocularium/svg/in1.trim.svg" class="boardimg noborder"/> <i>in1</i> </div> <div class="board_wrap"> <img src="/ocularium/svg/in2.trim.svg" class="boardimg noborder"/> <i>in2</i> </div> <div class="board_wrap"> <img src="/ocularium/svg/back.mirror.trim.svg" class="boardimg noborder"/> <i>reverse</i> </div> </div> </div> <div style="display: flex; flex-direction: column; width: 100%; align-items: center"> <i style="max-width: 75%" class="actual_size_disclaimer"> These board files are actual-size on your screen if your browser is at normal (100%) zoom. </i> <button id="zoom_boards" style="display: none; margin: 1rem">Toggle Zoom</button> </div> <p>The design is finished, and as of writing this post I'm just sending it out to be fabricated.</p> <object data="/ocularium/schematic/schematic.pdf" type="application/pdf" style="width: 100%; height: 500px"> <a href="/ocularium/schematic/schematic.pdf">Rendered Schematics (PDF)</a> </object> <p><a href="/ocularium/fab/gerbers.zip">gerbers.zip</a></p> <p><a href="/ocularium/fab/bom.csv">bom</a></p> <p><a href="/ocularium/fab/pos.csv">placement file</a></p> <p><strong>Warning</strong>: these production files <em>have not been validated</em> — I am in the process of converting to kikit (which generates them and puts them here) but spun the boards using <a href="https://github.com/bennymeg/Fabrication-Toolkit">Fabrication Toolkit</a>.</p> <h2 id="design">design</h2> <p>The board is 30x30mm with a 25x25mm M2 hole pattern. It's powered by a lithium cell via a battery controller, and uses an SD card for data storage. The sensors onboard are a six-axis accelerometer/gyro, a BME680 gas sensor (temperature, humidity, pressure, air quality), a lux sensor, and a MEMS microphone.</p> <p>Design goals:</p> <ul> <li>Small and light, to minimize impact on the kite's flight -- Chucho's previous solution was bulky/heavy and would pull the kite</li> <li>Useful / interesting sensor payload</li> <li>~4-hour endurance -- long enough to be forgiving about state of charge</li> <li>Low-cost</li> </ul> <h3 id="software-firmware">software / firmware</h3> <p>I'm writing the firmware in <a href="http://rust-lang.org">Rust</a> using the <a href="https://github.com/embassy-rs/embassy">embassy</a> family of embedded libraries.</p> <p>I am currently planning on writing a host-side UI in <a href="https://iced.rs/">iced</a>, which I've had luck with in the past (I'm using it for an in-progress mission UI for <a href="../antrelay">antrelay</a>).</p> <h2 id="future-work">future work</h2> <p>I will be tying this in with <a href="../interstice">interstice</a> as a networking test platform.</p> <h2 id="bringup-log">bringup log</h2> <h3 id="2024-08-22">2024-08-22</h3> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;board_assy_front.961d20d2d62c4827.jpg"> <i style="margin-top: 0.5rem"> <p>depaneled board, front</p> </i> </div> <p>Boards came in today. Production went well — they look great. I'm looking at a power issue: the <a href="https://www.ti.com/product/BQ25185">BQ25185</a> battery charger IC has a regulated output that I was using to supply 3.3V. Problem is that it's actually 4.5V — didn't catch this at design time. In retrospect, I think I had it as a placeholder part that I planned to replace (or augment with a DCDC), but it slipped through the cracks.</p> <p>Also have an ADC problem — I have VBAT, VUSB, and 3.3V connected to ADC lines, but I didn't add voltage dividers, so they're overvolting the ADCs and I suspect leaking through the ESD protection, if not damaging the silicon. I still have 2 untouched assembled boards if I already managed to burn one out.</p> <p>Going to have to respin, but provisionally powering 3.3V directly off of my bench supply to enable bringup on this rev and find any more issues.</p> <p>Tried to connect over SWD with an st-link clone, but it appears they <a href="https://community.st.com/t5/stm32-mcus-boards-and-hardware/swd-multidrop-does-any-stm32-or-st-link-support-it/td-p/80861">don't support multidrop</a>, which seems to be required for rp2040. Tried flashing <a href="https://github.com/blackmagic-debug/blackmagic">black magic probe</a>, which notionally addresses this, but it couldn't see the core. Ordered a few picos (I seem to have run out) to flash <a href="https://github.com/raspberrypi/debugprobe">picoprobe</a> onto, which I know will work.</p> <h3 id="2024-08-26">2024-08-26</h3> <div style="display: flex; flex-direction: column; align-items: center; padding: 1rem" class="vidwrap"> <video src="blink.webm" muted controls autoplay loop class="hover_controls" style="width: 480px; border-radius: 1rem" > </video> <i style="margin-top: 0.5rem"> <p>she blinks</p> </i> </div> <p>Got my picos set up as <a href="https://github.com/raspberrypi/debugprobe">picoprobes</a>, but no dice. Hooked up to my logic analyzer and saw well-formed SWD traffic. I don't know the protocol so couldn't tell if there was any response data, but I assumed not as <a href="https://probe.rs/"><code>probe-rs</code></a> complained that the device wasn't responding:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> probe-rs info<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>chip</span> rp2040<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>protocol</span> swd<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>target-sel</span> 0</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Probing</span></span><span class="z-meta z-function-call z-arguments z-shell"> target via SWD</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error</span></span><span class="z-meta z-function-call z-arguments z-shell"> showing ARM chip information: An ARM specific error occurred.</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Caused</span></span><span class="z-meta z-function-call z-arguments z-shell"> by:</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">0:</span></span><span class="z-meta z-function-call z-arguments z-shell"> An ARM specific error occurred.</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">1:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Failed to connect to the debug port. Please check the debug cable and target power. If SWD multi-drop is used, ensure the correct TARGETSEL value is used.</span> </span></code></pre> <p>My priority is get the rp2040 powering on and be able to flash code, so I moved on to triggering BOOTSEL mode. Shorted <code>QSPI_SS</code> to <code>GND</code> and plugged in via USB, but measured voltage on my power supply shot up to &gt; 3.5V and it wasn't sourcing any current, implying that the circuit was powering itself off of USB, even with the switch between <code>VSYS</code> (battery charger output, 4.5V — discussed in last entry) and 3.3V turned off. I don't know how — the only place VUSB goes other than the charger IC are the ADC pins. Could be something fried and bridged the nets, but in this whole process I've neither seen magic smoke nor noticed comonents getting warm — that's no more than speculation at the moment.</p> <p>On my last untouched board, I cut the VUSB traces right at the USB connector and verified open circuit to the regulator. Again shorted QSPI_SS to ground, powered on with my bench supply, and connected to USB.</p> <p>Linux tries to connect, but can't talk to the device:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> dmesg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427079.861946]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4-port3: attempt power cycle</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.457606]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: new low-speed USB device number 91 using ehci-pci</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.869588]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: device not accepting address 91, error<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>32</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.945619]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: new low-speed USB device number 92 using ehci-pci</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427081.357619]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: device not accepting address 92, error<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>32</span></span> </span></code></pre> <p>Seems like progress, but I logic analyzed this too, and the rp2040 isn't even trying to respond — the traffic on the bus is just the host sending <code>SETUP</code> and <code>DATA0 -&gt; GET_DESCRIPTOR</code> packets until it gives up.</p> <p>There is <em>something</em> happening on the board — when I power it, I see a reproducible pattern of power usage stabilizing at single-digit milliamps on my bench supply, but there's no way for me to tell at present whether that's from the RP2040 or any of the other ICs.</p> <h4 id="rescue-port">rescue port</h4> <p>Did some digging in the hardware design guide and saw this section about the rescue debug port:</p> <blockquote> <p>The rescue debug port (DP) on RP2040 can be used to reset the chip into a known state if the user has programmed some bad code into the flash. For example some code that turned off the system clock would stop the processor debug ports being accessed, but the rescue DP would still work because it is clocked from the SWCLK of the SWD interface.</p> </blockquote> <p>This seems like exactly what I want, because the whole contents of my flash are known to be garbage, as I've never flashed anything to the board before. The question of why I haven't been able to enter BOOTSEL mode is still open, but hopefully this will let me bypass it.</p> <p>It requires you to use the Raspberry Pi Foundation's <a href="https://github.com/raspberrypi/openocd">own independent fork of openocd</a> (the practice of forking off vendor-specific tooling continues to be a pain in the ass):</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> openocd<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>f</span> interface/cmsis-dap.cfg<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>f</span> target/rp2040-rescue.cfg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : Using CMSIS-DAPv2 interface with VID:PID=0x2e8a:0x000c, serial=<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">MY_SERIAL</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : CMSIS-DAP: Interface Initialised (SWD</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : CMSIS-DAP: Interface ready</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Now</span></span><span class="z-meta z-function-call z-arguments z-shell"> attach a debugger to your RP2040 and load some code</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> openocd<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>f</span> interface/cmsis-dap.cfg<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>f</span> target/rp2040.cfg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : Using CMSIS-DAPv2 interface with VID:PID=0x2e8a:0x000c, serial=<span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">MY_SERIAL</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : CMSIS-DAP: Interface Initialised (SWD</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : CMSIS-DAP: Interface ready</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : clock speed 100 kHz</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : SWD DPIDR 0x0bc12477, DLPIDR 0x00000001</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : SWD DPIDR 0x0bc12477, DLPIDR 0x10000001</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>rp2040.core0<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> Cortex-M0+ r0p1 processor detected</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>rp2040.core0<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> target has 4 breakpoints, 2 watchpoints</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>rp2040.core1<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> Cortex-M0+ r0p1 processor detected</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>rp2040.core1<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> target has 4 breakpoints, 2 watchpoints</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : starting gdb server for rp2040.core0 on 3333</span> </span></code></pre> <p>(<code>openocd</code> output substantially cleaned for readability).</p> <p>I connected with <code>gdb</code>, but this failed initially because it was trying to identify my SPI flash and <code>QSPI_SS</code> (= <code>~BOOTSEL</code>) was still shorted to <code>GND</code>:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : accepting <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>gdb<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span> connection on tcp/3333</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Unknown flash device (ID 0x00ffffff</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error:</span></span><span class="z-meta z-function-call z-arguments z-shell"> auto_probe failed</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Connect failed. Consider setting up a gdb-attach event for the target to prepare target for GDB connect, or use <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>gdb_memory_map disable<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span>.</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error:</span></span><span class="z-meta z-function-call z-arguments z-shell"> attempted <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>gdb<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span> connection rejected</span> </span></code></pre> <p>Fixed by opening this short:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : accepting <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>gdb<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span> connection on tcp/3333</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : Found flash device <span class="z-string z-quoted z-single z-shell"><span class="z-punctuation z-definition z-string z-begin z-shell">&#39;</span>win w25q128fv/jv<span class="z-punctuation z-definition z-string z-end z-shell">&#39;</span></span> (ID 0x001840ef</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : RP2040 B0 Flash Probe: 16777216 bytes @0x10000000, in 256 sectors</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Info</span></span><span class="z-meta z-function-call z-arguments z-shell"> : New GDB Connection: 1, Target rp2040.core0, state: halted</span> </span></code></pre> <p>And then flashed blinky firmware:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> gdb</span> </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">(gdb</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">target</span></span><span class="z-meta z-function-call z-arguments z-shell"> extended-remote localhost:3333</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Remote</span></span><span class="z-meta z-function-call z-arguments z-shell"> debugging using localhost:3333</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">0x00000030</span></span><span class="z-meta z-function-call z-arguments z-shell"> in <span class="z-keyword z-operator z-regexp z-quantifier z-shell">?</span><span class="z-keyword z-operator z-regexp z-quantifier z-shell">?</span> (</span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">(gdb</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">file</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">MY_BLINKY</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">A</span></span><span class="z-meta z-function-call z-arguments z-shell"> program is being debugged already.</span> </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">Are you sure you want to change the file<span class="z-keyword z-operator z-regexp z-quantifier z-shell">?</span> (y or n</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">y</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Reading</span></span><span class="z-meta z-function-call z-arguments z-shell"> symbols from <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">MY_BLINKY</span></span>...</span> </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">(gdb</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">load</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Loading</span></span><span class="z-meta z-function-call z-arguments z-shell"> section .boot2, size 0x100 lma 0x10000000</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Loading</span></span><span class="z-meta z-function-call z-arguments z-shell"> section .vector_table, size 0xc0 lma 0x10000100</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Loading</span></span><span class="z-meta z-function-call z-arguments z-shell"> section .text, size 0x4cd8 lma 0x100001c0</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Loading</span></span><span class="z-meta z-function-call z-arguments z-shell"> section .rodata, size 0xaac lma 0x10004ea0</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Loading</span></span><span class="z-meta z-function-call z-arguments z-shell"> section .data, size 0xb4 lma 0x1000594c</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Start</span></span><span class="z-meta z-function-call z-arguments z-shell"> address 0x100001c0, load size 23032</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Transfer</span></span><span class="z-meta z-function-call z-arguments z-shell"> rate: 1 KB/sec, 3838 bytes/write.</span> </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">(gdb</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">run</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">The</span></span><span class="z-meta z-function-call z-arguments z-shell"> program being debugged has been started already.</span> </span><span class="z-source z-shell z-bash"><span class="z-punctuation z-definition z-compound z-begin z-shell">(</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ins</span></span><span class="z-punctuation z-definition z-compound z-end z-shell">)</span><span class="z-meta z-function-call z-arguments z-shell">Start it from the beginning<span class="z-keyword z-operator z-regexp z-quantifier z-shell">?</span> (y or n</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">y</span></span> </span></code></pre> <div style="display: flex; flex-direction: column; align-items: center; padding: 1rem" class="vidwrap"> <video src="blink.webm" muted controls autoplay loop class="hover_controls" style="width: 480px; border-radius: 1rem" > </video> </div> <p>And now <code>probe-rs run</code> (via <code>cargo run</code>) works:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> cargo run</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Finished</span></span><span class="z-meta z-function-call z-arguments z-shell"> dev <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>optimized + debuginfo<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> target(s</span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">in</span></span><span class="z-meta z-function-call z-arguments z-shell"> 0.12s</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Running</span></span><span class="z-meta z-function-call z-arguments z-shell"> <span class="z-meta z-group z-expansion z-command z-backticks z-shell"><span class="z-punctuation z-section z-group z-begin z-shell">`</span><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">probe-rs</span></span><span class="z-meta z-function-call z-arguments z-shell"> run<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>chip</span> RP2040 target/thumbv6m-none-eabi/debug/blinky</span><span class="z-punctuation z-section z-group z-end z-shell">`</span></span></span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Erasing</span></span><span class="z-meta z-function-call z-arguments z-shell"> ✔ <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>00:00:00<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>############################<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> 24.00 KiB/24.00 KiB @ 66.55 KiB/s (eta 0s </span><span class="z-meta z-function-call z-shell"></span>) </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Programming</span></span><span class="z-meta z-function-call z-arguments z-shell"> ✔ <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>00:00:00<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> <span class="z-keyword z-control z-regexp z-set z-begin z-shell">[</span>############################<span class="z-keyword z-control z-regexp z-set z-end z-shell">]</span> 24.00 KiB/24.00 KiB @ 42.71 KiB/s (eta 0s </span><span class="z-meta z-function-call z-shell"></span>) <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Finished</span></span><span class="z-meta z-function-call z-arguments z-shell"> in 0.95s</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">0.001210</span></span><span class="z-meta z-function-call z-arguments z-shell"> INFO boot</span> </span></code></pre> <p><code>probe-rs info</code> works, but it locks up the core and <code>probe-rs reset</code> doesn't reset it:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> probe-rs info<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>chip</span> rp2040<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>protocol</span> swd</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Probing</span></span><span class="z-meta z-function-call z-arguments z-shell"> target via SWD</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">ARM</span></span><span class="z-meta z-function-call z-arguments z-shell"> Chip:</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Debug</span></span><span class="z-meta z-function-call z-arguments z-shell"> Port: Version 2, MINDP, Designer: Raspberry Pi Trading Ltd, Part: 0x1002, Revision: 0x0</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> probe-rs reset<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>chip</span> rp2040<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> --</span>protocol</span> swd</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Error:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Connecting to the chip was unsuccessful.</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">Caused</span></span><span class="z-meta z-function-call z-arguments z-shell"> by:</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">0:</span></span><span class="z-meta z-function-call z-arguments z-shell"> An ARM specific error occurred.</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">1:</span></span><span class="z-meta z-function-call z-arguments z-shell"> An ARM specific error occurred.</span> </span><span class="z-source z-shell z-bash"> <span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">2:</span></span><span class="z-meta z-function-call z-arguments z-shell"> Failed to connect to the debug port. Please check the debug cable and target power. If SWD multi-drop is used, ensure the correct TARGETSEL value is used.</span> </span></code></pre> <p>This last note about multidrop/TARGETSEL could be the solution, but there isn't a flag to set TARGETSEL for <code>probe-rs reset</code>. Fine in the end — I can manually reset with the power supply.</p> <h3 id="2024-08-27">2024-08-27</h3> <p>Working on USB, seeing the same issue as before: host sees the pull-up and tries to contact the device a few times before giving up:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> dmesg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427079.861946]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4-port3: attempt power cycle</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.457606]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: new low-speed USB device number 91 using ehci-pci</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.869588]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: device not accepting address 91, error<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>32</span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427080.945619]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: new low-speed USB device number 92 using ehci-pci</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1427081.357619]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 2-1.4.4.3: device not accepting address 92, error<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>32</span></span> </span></code></pre> <p>I'm testing with firmware that I've flashed to a <a href="https://www.seeedstudio.com/XIAO-RP2040-v1-0-p-5026.html">XIAO RP2040</a>, which successfully establishes a high-speed link and opens a CDC-ACM port which is recognized by the host computer. Expected output:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> dmesg</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.033057]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 1-1.5: new full-speed USB device number 22 using ehci-pci</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.113650]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 1-1.5: New USB device found, idVendor=8888, idProduct=0001, bcdDevice= 0.10</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.113655]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 1-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=0</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.113656]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 1-1.5: Product: <span class="z-meta z-group z-expansion z-parameter z-shell"><span class="z-punctuation z-definition z-variable z-shell">$</span><span class="z-variable z-other z-readwrite z-shell">PRODUCT</span></span></span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.113657]</span></span><span class="z-meta z-function-call z-arguments z-shell"> usb 1-1.5: Manufacturer: npry</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">[1506678.114587]</span></span><span class="z-meta z-function-call z-arguments z-shell"> cdc_acm 1-1.5:1.0: ttyACM1: USB ACM device</span> </span></code></pre> <p>Probed voltage on D+ and I'm seeing 3.0V with a cable plugged in rather than expected 3.3V for LS operation. D- is at ground potential. Possibly an issue with drive strength on the USB peripheral on the RP2040? But apparently 2.8V is the specified signaling minimum, so perhaps this shouldn't be surprising. Tried a few different USB cables that have been known to work and different ports on the host, no dice.</p> <p>Probed D+ with USB cable disconnected and I'm seeing 3.20V, which for me counts as effectively nominal for a specified 3.3V.</p> <p>Tried shorting the 27.4Ω impedance-matching resistors just for something to try — no change.</p> <h4 id="cc2-vconn">cc2 / vconn</h4> <p>Found an issue on my schematic: CC2 wasn't terminated — I left it floating. Another thing I intended to get back to at the time, but didn't, and then by the time I went to ship the board, I assumed past-me had validated it.</p> <p>I'm testing with a USB A-to-C cable, which I suppose must internally have orientation detection logic, so this seems a likely culprit — I definitely need to fix it for the next rev. However, now I'm thinking back to the fact that I got a signal that looked fine on a scope and decoded as valid host-to-device control packets with a logic analyzer, probed right at the impedance-matching resistors next to the rp2040 pins.</p> <p>I <em>have</em> kept coming back to this idea that maybe my data lines are backwards, but I've checked several times, and they weren't. Then again, I've only been checking by looking at the voltage at D+, the pull-up for which is device-supplied, so possibly that's not a reliable test. And when I scoped/ logic-analyzed the traffic, I was looking at the BOOTSEL behavior, so there could be another confounding issue.</p> <p>Next thing I guess is to properly terminate CC2 and see if that makes a difference.</p> <h2 id="2024-09-22">2024-09-22</h2> <p>Been almost a month since my last update — haven't gotten around to writing progress up. Mostly been working on <a href="../molybdos">molybdos</a> as a basis for the firmware, converting chunks of old projects (e.g. <a href="../janus">janus</a>, <a href="../hexrx">hexrx</a>) to portable library code, and porting third-party sensor libraries to async (<a href="https://pub.npry.dev/drogue_bme680_async">bme680</a>, <a href="https://pub.npry.dev/lsm6dsm">lsm6dsm</a>, <a href="https://pub.npry.dev/veml7700_async">veml7700_async</a>).</p> <p>The problem with USB <em>was</em> swapped polarity on the data lines — I was able to rework it and verify the fix. I thought it was a footprint issue initially, but I actually just swapped them in the schematic at the decoupling resistors.</p> <p>Also discovered that I got my I2C lines wrong — they're attached to different MCU peripherals. There doesn't seem to be a good software or PIO I2C implementation in Rust yet — I started writing a PIO one based on the example in the RP2040 C SDK, but decided the verification overhead wasn't worth it right at this moment. Going to test by breaking out the bus and connecting with my Bus Pirate or a Xiao board.</p> <h2 id="2024-09-24">2024-09-24</h2> <p>Got a PIO I2S driver semi-working — enough to get working PDM audio back. Scaling the bits to <code>i16::MAX</code> and <code>i16::MIN</code> is enough to get recognizable but choppy sound out of it.</p> <p>The issue I'm dealing with is that the DMA shots from the PIO FIFOs to memory are taking way longer (40x) than they should. I'm not sure yet whether I'm miscalculating my clock, am missing something about PIO functionality, or if it's something with the host MCU (backpressure or scheduling). I'm running the read loop in the regular thread-mode executor, so it could just be a scheduling issue (though there shouldn't be any other futures running concurrently, so that's kind of dubious). Next thing I'll try is a dedicated higher-priority interrupt executor just because it's easy.</p> <p>That said, not going to bother for now. I can hear audio, so I know it's working enough to proceed with the next rev.</p> <p>Confirmed that the BME is reachable over its SPI bus by reading its chip id. Not going to bother trying to read data off of it, just made sure I can talk to it.</p> <h2 id="2024-09-25">2024-09-25</h2> <p>Took a look at the SD card today — it wasn't working right off the bat. Looks like I flipped the MOSI and MISO lines (guessing I feel victim to the SDO/SDI terminology mismatch: CMD is "data in" but "master out" / DAT0 is "data out" but "master in", and I matched on the wrong role). Reworking this would be a pain in the ass because the pins are tiny, so I'm going to just blindly respin it.</p> <p>Also relevant: last week or so, I broke out <a href="https://pub.npry.dev/embedded_sdmmc_async">my fork</a> of <code>embedded_sdmmc</code> from the <a href="https://pub.npry.dev/hexrx">hexrx</a> firmare as a standalone repo.</p> <h2 id="2024-09-26">2024-09-26</h2> <p>Had to find my <a href="https://www.sparkfun.com/products/12942">bus pirate</a> yesterday — ran I2C sanity checks today:</p> <h3 id="bus-scan">bus scan</h3> <pre class="z-code"><code><span class="z-text z-plain">I2C&gt;(1) </span><span class="z-text z-plain">Searching I2C address space. Found devices at: </span><span class="z-text z-plain">0x20(0x10 W) 0x21(0x10 R) 0xD6(0x6B W) 0xD7(0x6B R) </span></code></pre> <p>Correctly found the VEML7700 at 0x10 and the LSM6DSM at 0x6B.</p> <h3 id="lsm6dsm">lsm6dsm</h3> <p>Find <code>WHOAMI</code> reg (0x0f):</p> <pre class="z-code"><code><span class="z-text z-plain">I2C&gt;[0xd6 0x0f [0xd7 r] </span><span class="z-text z-plain">I2C START BIT </span><span class="z-text z-plain">WRITE: 0xD6 ACK </span><span class="z-text z-plain">WRITE: 0x0F ACK </span><span class="z-text z-plain">I2C START BIT </span><span class="z-text z-plain">WRITE: 0xD7 ACK </span><span class="z-text z-plain">READ: 0x6A </span><span class="z-text z-plain">NACK </span><span class="z-text z-plain">I2C STOP BIT </span></code></pre> <p>Sees correct value 0x6a.</p> <h3 id="veml7700">veml7700</h3> <p>chipid reg at 0x7:</p> <pre class="z-code"><code><span class="z-text z-plain">I2C&gt;[0x20 0x7 [0x21 rr] </span><span class="z-text z-plain">I2C START BIT </span><span class="z-text z-plain">WRITE: 0x20 ACK </span><span class="z-text z-plain">WRITE: 0x07 ACK </span><span class="z-text z-plain">I2C START BIT </span><span class="z-text z-plain">WRITE: 0x21 ACK </span><span class="z-text z-plain">READ: 0x81 </span><span class="z-text z-plain">READ: ACK 0xC4 </span><span class="z-text z-plain">NACK </span><span class="z-text z-plain">I2C STOP BIT </span></code></pre> <p>16 bit registers, default configuration is 0xC4 with address 0x81 — checks out.</p> <h2 id="respin-todo">respin todo</h2> <ul> <li><input disabled="" type="checkbox" checked=""/> 3V3 regulator</li> <li><input disabled="" type="checkbox" checked=""/> fix cc termination</li> <li>adc <ul> <li><input disabled="" type="checkbox" checked=""/> voltage dividers</li> <li><input disabled="" type="checkbox" checked=""/> voltage reference</li> </ul> </li> <li><input disabled="" type="checkbox" checked=""/> purple LED -&gt; change to blue (too dim)</li> <li><input disabled="" type="checkbox" checked=""/> esd protection <ul> <li>VBUS, D+/D-</li> <li>SWCLK, SWDIO</li> </ul> </li> <li><input disabled="" type="checkbox" checked=""/> usb data polarity</li> <li><input disabled="" type="checkbox" checked=""/> i2c pin fix</li> <li>sd card fixes <ul> <li><input disabled="" type="checkbox" checked=""/> fix mosi/miso flip</li> <li><input disabled="" type="checkbox" checked=""/> (optional) card detect</li> </ul> </li> <li><input disabled="" type="checkbox" checked=""/> connect sensor hub to i2c (solder jumpers, default-open)</li> <li><input disabled="" type="checkbox" checked=""/> connect bme to i2c</li> <li><input disabled="" type="checkbox" checked=""/> switch to proper i2s part</li> </ul> 2024-08-01T00:00:00+00:00 2024-08-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/home-lab/ <h2 id="electronics">electronics</h2> <ul> <li><a href="https://www.amazon.com/dp/B06XZML6RD">Siglent SDS-1202X-E 2-channel Oscilloscope</a>: $350</li> <li><a href="https://www.amazon.com/dp/B07K6HXDH1">USB Logic Analyzer</a>, $14 <ul> <li>Works in <a href="https://www.saleae.com/pages/downloads">Saleae Logic</a>, which is the most important part of their package for me. Most of the time I don't need the super high sample rates, analog channels, or independent per-channel grounds, but being able to write an <a href="https://support.saleae.com/extensions/high-level-analyzer-extensions">HLA</a> is great.</li> </ul> </li> <li><a href="https://store.arduino.cc/products/ts80p-main-smart-soldering-iron">TS-80 USB-C powered soldering iron</a> <ul> <li>At the Media Lab I use a <a href="https://pine64.com/product/pinecil-smart-mini-portable-soldering-iron/">Pinecil</a> at my desk — quite happy with both</li> </ul> </li> <li><a href="https://amscope.com/products/se305r-p">AmScope SE305 binocular microscope</a></li> <li>Cheap lab power supply</li> </ul> <h2 id="3d-print">3d-print</h2> <ul> <li><a href="https://www.creality.com/products/ender-3-3d-printer">Creality Ender 3</a> <ul> <li>With <a href="https://www.antclabs.com/bltouch">BLTouch</a></li> <li>With <a href="https://www.creality3dofficial.com/products/creality-silent-mainboard-v4-2-7">silent mainboard (trinamic drivers)</a> running <a href="https://www.klipper3d.org/">Klipper firmware</a></li> <li>With raspi running <a href="https://nixos.org/">NixOS</a>, Klipper, <a href="https://moonraker.readthedocs.io/en/latest/">moonraker</a>, and controlled via <a href="https://docs.mainsail.xyz/">mainsail</a></li> </ul> </li> <li><a href="https://store.anycubic.com/products/anycubic-photon-s">Anycubic Photon S</a></li> </ul> <h2 id="compute">compute</h2> <ul> <li>Modern desktop: 12700KF, 64GB DDR5, 3080Ti. Dual boots Windows 10 and <a href="https://nixos.org/">NixOS</a> — I spend most of my time in Windows.</li> <li>Older desktop: 4770, 16GB DDR4 — runs NixOS, more of a dedicated lab pc</li> </ul> 2024-07-25T00:00:00+00:00 2024-08-10T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/tmc5240/ <div style="display: flex; flex-direction: column; align-items: center; padding: 1rem" class="vidwrap"> <video src="stepper_spin.webm" muted controls loop class="hover_controls" style="width: 480px; border-radius: 1rem" > </video> <i style="margin-top: 0.5rem"> <p>she spins</p> </i> </div> <p>I wrote a <a href="https://github.com/zephyrproject-rtos/zephyr/commit/c3f45bcbe9aec9833921ce157db1bd04390f775c">Zephyr driver</a> over the past week or two for the <a href="https://www.analog.com/en/products/tmc5240.html">tmc5240</a> (<a href="https://perrynaseck.com/">Perry</a>'s project). It speaks SPI, adheres to a <a href="https://github.com/zephyrproject-rtos/zephyr/pull/68774">new stepper API Perry is involved with</a>, and provides <a href="https://github.com/zephyrproject-rtos/zephyr/blob/c3f45bcbe9aec9833921ce157db1bd04390f775c/include/zephyr/drivers/stepper/tmc5240.h">device-specific functionality</a> such as pipelined SPI transactions, full register load/dump, and a Kconfig-urable shadow register file.</p> <p>I did this to help Perry out and because he's offered to give me access to some of his boards, which look like a good test and demo platform for <a href="../interstice">interstice</a>.</p> <h2 id="zephyr-reflections">zephyr reflections</h2> <p>It's basically like Linux kernel dev. Everything is Kconfig, it's based on device tree, the functions look POSIX-y (all of this intentionally, I'm sure). This is nice in that the API and general conventions are known / comparable, but not-so-nice in that the knowledge barrier is huge and implicit. Yes, there are manuals to rtf, but they're really there to guide you on the presumption that you're already mostly familiar with the environment. For embedded, having consistent abstractions and not a vendor hal is great. Device-tree remains a lesser evil.</p> <p>I'm glad I did this to see what it's like, and I think if you're writing embedded C in anger, Zephyr's probably one of the absolute best options. I probably wont pick it up for a personal project, though, unless I'm armtwisted into it (e.g. if I <em>really need</em> the <a href="https://github.com/nrfconnect/sdk-nrf">nRF Connect SDK</a>) — Rust is just too expressive by comparison, especially for the <a href="../interstice">kinds of things</a> I have planned on embedded. I think I could have written this driver in substantially less than half the time in Rust, with better ergonomics, and for a non-vendor-locked interface abstraction (<a href="https://docs.rs/embedded-hal-async/latest/embedded_hal_async/spi/trait.SpiDevice.html"><code>embedded_hal_async::spi::SpiDevice</code></a>).</p> 2024-06-24T00:00:00+00:00 2024-06-24T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/thesis/pitch-old/ <div style="background: var(--dimYellow); padding: 0.25rem 1rem; border: var(--yellow) 2px dashed; border-radius: 1rem; margin-top: 1rem"> <p><strong>this document describes an outdated vision of my work, and is preserved for reference.</strong></p> <p><strong>please see the current revision <a href="../thesis-pitch">here</a>.</strong></p> </div> <p>An economy can be viewed as a framework for coordinating a massive multi-agent system by allowing it to express incentives that conduce to useful work over an extended timescale. Humanity, writ large, represents an adaptable, self-scaling swarm intelligence, despite being composed of fully independent autonomous agents, who share approximate incentives and are coordinated at the macro scale by economic forces. Consider what economic development looks like, at a long time scale and birds-eye view. Humans grow in fractals -- they follow incentives, gather around resource centers, and reproduce themselves to exploit surplus. This effect can be observed on timescales of hours and days with groups of dozens up to decades and centuries with populations of tens of millions: there is a direct analogy to bacterial colonies reproducing in Petri dishes and ants building nests.</p> <p>Most large physical systems scale this way -- they are composed of autonomous individual units following incentive gradients. The notion of incentive and the space in which it is embedded varies greatly between physical species, from spatial nutrient density for single-celled organisms to sophisticated, high-dimensional notions of value incorporating explicit, codified social structures, language, tradition, experience, and so on, as humans do. What remains interesting about this world model, despite the differences in objective function between bacterium and human, is that humans still scale in the real world more or less like bacterial colonies once you zoom out far enough. Bacteria are contained to the Petri dish -- they are not structurally sophisticated enough to have an understanding of the world around them or meaningful ability to leap energy thresholds to exploit remote resources. Bacteria are effectively spatially confined to resource areas, and have little to no ability to expand beyond that. Bacterial colonies cannot, except accidentally, spread to an adjacent Petri dish, no matter how high the nutrient density (and hence notional incentive) because they cannot collectively sense beyond their colonies and have no structural capability to actuate in the world.</p> <p>Humans, by contrast, are able to do exactly that. We build logistics networks to transport utility away from production sites, expanding our reach. Human history is a story of repeated expansion beyond a succession of these archetypal Petri dishes, as advances in science and technology enable us to reach beyond our current capabilities and express structure in the universe at grander and grander scales. The most substantial and rapid advances have been due to the commodification of microelectronics and capacity to embed and express computation ubiquitously. But this capability has not yet converged with the human species' ability to scale actuation. We use electronic computation to manage logistics and enable more rapid and wide-area communication. But our models for integrating automation into actuation on the world -- actually scaling our resource cultivation and exploitation capabilities -- have not yet come to fruition. We are starting to see the beginning of this process, but we don't see large numbers of robots participating in economic activity in a scalable way.</p> <p>On the face of it, this statement appears wrong -- robotic automation is everywhere in mass manufacturing, and automated systems manage inventories, investment, logistics, and more. But they are not <em>integrated</em> in the recursive, fractal, log-boundary-crossing way that living systems are. Automated systems are leaves in the graph conceived and purpose-built for a single application. They are not robust in the sense that they admit of a composition of modular, independent agents that are straightforwardly replaced, which communicate and negotiate in order to produce mutually-beneficial results that conduce towards economic incentives. Assembly lines are hard-coded, prebaked, and require human intervention for all maintenance.</p> <p>Research in drone and swarming applications mostly does not look at this problem, and is instead concerned with optimality and efficiency of acutation control. While the results of this research are interesting, they make the essential mistake of disregarding investigations of communications and network topology in favor of easier-to-implement centralized control. This makes most of these results functionally unusable for implementing a living system of the kind I describe, as the agents are not independent or self-motivated but limbs of a central brain.</p> <p>My resources to address this problem are relatively constrained. I work in a hardware group without a strong history of drone research. We don't have terribly deep prior connections nor an existing drone lab to &lt;...&gt;. I don't have much funding to work with. Hence I will be strategic in my approach to proving out this perspective.</p> <p>The most useful thing to build is a prototype for the concept -- something that demonstrates a simple but unsophisticated living system that can work as a demo and testbed. This is what I intend to do with my master's thesis. It will be a mixed sim-real digital twin environment supporting a swarm of drones that initially can be controlled by a human directly.</p> <p>I plan to produce a simulation amenable to wide-area, large-unit-count drone control by a human operator, using interfacing paradigms inspired by real-time-strategy (RTS) video games (notably StarCraft II, Beyond All Reason), which have proven effective for this actuation mode. I intend to demonstrate mixed sim-real operation in a digital twin model of a test space, enabling a small number of physical drones (five to ten) to act as a representative subset of a complete virtual swarm of up to hundreds of members, validating behaviors in the real world, helping the simulation converge towards real behavior, and acting as demonstration aids. Taking additional inspiration from the RTS game genre, individual drones will be of limited local intelligence: capable of locomotion, basic obstacle and neighbor avoidance, and a small command library, deferring to the human controller for all higher-level planning and decision-making.</p> <p>I hope to demonstrate that under an appropriate interfacing paradigm, this limited drone intelligence can be leveraged by a single human operator to rapidly complete wide-area tasks such as object cleanup, delivery logistics, surveillance, interdiction, and sensor deployment / recovery. The goal is to show that this approach provides a substantial productivity multiplier compared with manual human operation, without requiring complicated, training-intensive, motivationally-opaque behavior implemented via ML or RL. I intend to demonstrate that this approach is also amenable to remote control, even with significant actuation and sensing latency.</p> <p>This approach is exciting because RTS games supply a proven, robust interfacing paradigm that supports sustainable human control of hundreds of independent agents at an actuation rate of hundreds of discrete inputs per minute – actions which are leveraged in a context of evolving, goal-oriented human tactical and strategic decisionmaking, which directly mirrors many forms of real-world productive work. The RTS genre provides a clear model for separation of agent and human responsibilities, making the agent relatively dumb (and therefore easy to implement), but proves that this extremely minimal form of autonomy is sufficient to enable a human operator to produce wide-area effects rapidly and effectively.</p> <p>To tie this back to the conceptual motivation, the point of this work is to demonstrate that highly-scalable swarms are possible now, implementable by leveraging human intelligence as the strategic and tactical control and keeping individual drone behavior simple and understandable. The abstraction boundary provided by the agent-human interface provides a natural modularization surface that simplifies implementation, enabling me to demonstrate results quickly, but is readily suited to incremental improvements in capability as the work progresses.</p> 2024-04-04T00:00:00+00:00 2024-04-04T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/casette/ <script type="module" src="https://ajax.googleapis.com/ajax/libs/model-viewer/3.4.0/model-viewer.min.js"></script> <p><model-viewer src="casette.glb" shadow-intensity="1" modes="scene-viewer quicklook" tone-mapping="commerce" camera-controls touch-action="pan-y" style="width: 600px; height: 600px;"></model-viewer></p> <p>For my <a href="../pcb-system">two-sided PCB mill</a>, I'm designing a casette that carries the FR-1 blank. The aim is to put indexing features on the casette rather than milling them into the blank.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;casette_initial.5b13407f4c11b31f.jpg"> </div> <p>This solves a whole bunch of problems mechanically that otherwise would require rather more involved solutions (a vision system, milled locating pins that would require manipulation, etc.).</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;flipper.bd30218c2b282442.jpg"> </div> <p>The first design (above) is a two-part carrier held together with M5 bolts and heatset inserts. The top and bottom pieces are identical and symmetrical about 180 degree flips.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;casette_gap.5f3b0a968d34fcab.jpg"> </div> <p>Unfortunately (and unsurprisingly) this design has a gap in the center where there is no clamping force. The second design adds bolts to apply clamping force here:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;iteration_2.ccaf5970a0587b63.jpg"> </div> <p>And adds the <a href="https://clank.tools/tools/">Kleat</a> kinematic mount:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;kleat_mount.bc3b59c4b372c7d9.jpg"> </div> <p>Next iteration will adjust the Kleat mounting point and pin lengths so they don't collide. I'm still solving for the interaction between the mount and the board-flipping system.</p> <h3 id="considerations-clamping-force">considerations: clamping force</h3> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;current_state.16aadea7398f1c57.jpg"> </div> <p>Another way to solve the center-clamping problem would be to print the casette bowed out / as a spring that must meet in the center first and is then preloaded using the bolts on the edges.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;spring.9314921d25eb9937.jpg"> </div> <p>This would be nice in that it would reduce part count and presumably clamping uniformity (the current solution of additional screws along the long edges I expect has a tendency to pinch only the outside edge of the board). However, this approach would make 3d printing very annoying, as I'm using the inner face as a flat surface that doesn't require support. Additionally, I expect PLA/PETG to creep, so I would anticipate clamping force to drop off over time using this approach. Perhaps it's acceptable?</p> <p>The other obvious way I can think to approach this is printing the parts flat, then heat-softening and molding them to have that slight curve. Doing this would require a jig and a heater, but might be worth it.</p> 2024-04-03T00:00:00+00:00 2024-08-10T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/research/ <h2 id="embedded-sucks">embedded sucks</h2> <p>for anachronistic, unnecessary, solvable reasons</p> <ul> <li> <p>no os and c/c++ are basically not reusable / this is such a pain that people don't do it, and when they do, it's very poor quality</p> </li> <li> <p>or you have an rtos and are locked into their ecosystem</p> </li> <li> <p>rust is great</p> <ul> <li>a language package manager, wow</li> <li>many usable <code>#![no_std]</code> libraries</li> <li>no vendor lock-in with rtos -- embassy is the most central thing, but almost all of the components work independent of any runtime</li> <li>it's still a pain in the ass to setup (hence <a href="https://public.git.npry.dev/molybdos"><code>molybdos</code></a>)</li> </ul> </li> <li> <p>there are a bunch of <a href="https://www.aliexpress.us/item/3256804850399956.html"><em>very</em> low cost microcontrollers</a> ($0.10) out there. it often makes sense in an embedded project to offload work to another processor, but usually a single mcu only has one core. so add more! but you often need to write your own primitive networking stack to have them talk to each other, and that integration complexity makes it not worthwhile</p> <ul> <li>however, we've solved this problem already. we have a lot of mature networking standards and software, and the reason they're not on embedded is how people wrote them and how they're packaged, not that they're not fit for purpose</li> <li>in rust this isn't an issue -- look at <a href="https://blog.npry.dev/resenv/research/%22https://github.com/embassy-rs/embassy/tree/main/embassy-net%22"><code>embassy_net</code></a>, <a href="https://github.com/rust-embedded-community/embedded-nal"><code>embedded_nal</code></a>, and <a href="https://github.com/smoltcp-rs/smoltcp"><code>smoltcp</code></a>. these are intentionally intercompatbile networking interface definitions that are a de-facto standard for embedded rust.</li> <li>hence <a href="https://public.git.npry.dev/interstice"><code>interstice</code></a> -- embassy already has a ppp implementation that wraps <code>embedded_io_async::{Read,Write}</code> types (e.g. UARTs), we just need a packet switch to bridge multiple L2 links</li> </ul> </li> <li> <p>what else is nice? just having an operating system -- then you don't need a different software kind for bare-metal</p> <ul> <li><a href="https://wiki.pine64.org/wiki/Ox64">Ox64</a> + elixir + rust</li> </ul> </li> </ul> <h2 id="minimum-cost-hardware">minimum cost hardware</h2> <ul> <li> <p>lots of "open source hardware" publishes the schematics and firmware but not the board design. this is a fine model but it also means there are a lot of designs out there that are way more expensive than the components and in reach for to relayout (optionally publish) and use for myself</p> <ul> <li>e.g.: <ul> <li>vesc</li> <li>crazyflie</li> </ul> </li> <li>basically, it's not really open source hardware if it doesn't have a bom and design files — should be a single digikey order + basically 1 click from jlc</li> </ul> </li> <li> <p>embarassingly parallel physical problems</p> <ul> <li>drones suggest themselves as the obvious thing</li> <li>"beach cleanup"-type -- keep adding units with simple logic</li> <li>rts control -- 2.5d paradigm</li> </ul> </li> <li> <p>drone swarms for useful work</p> <ul> <li>so far they don't do this -- only single-operator or preplanned missions</li> </ul> </li> <li> <p>dumbing down drone control</p> <ul> <li>what is an actually-useful mvp for a drone swarm?</li> <li>things only need to be able to see "good enough" and share information</li> <li>super high-fidelity is probably not that great</li> </ul> </li> <li> <p>...</p> </li> </ul> 2024-03-21T00:00:00+00:00 2024-04-11T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/clank-build/ <p><em>clank: current state</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;2024_04_11_update.4fe47572113f7c55.jpg"> </div> <p>I've fixed mounting issues for the x-axis gantry, tensioned the belts, and built/installed the z-axis and Kleat holder mechanism.</p> <p>The main item still remaining on the base machine is the shaft for the pulley/mechanical stepdown on the on the Z-axis. This is required for me to mount the Z motor — I've threaded the belt through in preparation.</p> <h3 id="belt-tensioner">belt tensioner</h3> <p>I designed and 3d printed (out of PETG) a simple belt tensioner:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;belt_tensioner.5756eef384015fa8.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;belt_tensioner_installed.4c77ecead4f1b0ba.jpg"> </div> <p>It screws into a T-nut in the 80/20 and uses another M5 screw to jack the belt tight. Had some issues with imperfect mounting of the threaded insert producing torque/rotation on the idler stackup, but it worked sufficiently well to get all the belts tight.</p> <h2 id="2024-03-21">2024/03/21</h2> <p><em>clank: state as of 2024/03/11</em> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clank_base.5f34842612f09467.jpg"> </div> </p> <p>I built my clank-stretch / mini-zund / data printer (CSMZDP?) this week — thank you to Jake for sourcing and arranging all the materials and prints.</p> <h3 id="minor-build-issues">minor build issues</h3> <p>Hit a couple of snags building -- sent along to Jake.</p> <p><em>Linear rail mounts for tool carriage had a tendency to break if printed in this orientation. Fixed by printing holes vertically.</em> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clank_z_break.06812924bd39127f.jpg"> </div> </p> <p><em>Missing screw hole on Y-axis motor mounts. Since fixed in the CAD.</em> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clank_missing_screw.0b75b71420b01fbb.jpg"> </div> </p> <p><em>X-axis belt clearance issue — mine rubs currently. I think I can fix by removing some plastic with a file.</em> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clank_belt.ba541c66a1722bcc.jpg"> </div> </p> <h3 id="improvements-todo">improvements todo</h3> <ul> <li> <p>[<a href="https://blog.npry.dev/class/machines/clank-build/#belt-tensioner">DONE</a>] Idler tensioner fixture (to CAD + print)</p> <ul> <li>T-nut in 8020, screw at 90 degrees (on X-Y plane) that you can tighten to jack the idler assembly tighter. Unscrew when done / reusable.</li> </ul> </li> <li> <p>Jig for idler stackup assembly (to CAD + print)</p> <ul> <li>Really a pain in the ass to set these up if the tolerances aren't on the right side of the relevant line — sometimes very hard to get the part into a vice / press to get the bearings on. I think there's a relatively simple 3D-printed part that could make this easy.</li> </ul> </li> </ul> 2024-03-14T00:00:00+00:00 2024-04-04T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/ip-embedded/ <p><strong>library link</strong>: <a href="https://public.git.npry.dev/interstice">https://public.git.npry.dev/interstice</a> (placeholder currently)</p> <p>As <a href="https://ekswhyzee.com/2024/03/09/mudlink.html">Jake has written about</a>, there is a lack of easy networking / communication on embedded, prompting his implementation of MUDL (and my <a href="../mudlrs">Rust port</a>).</p> <p>To motivate more directly: it is frankly a pain in the ass to make a microcontroller talk to anything, and communication is normally at some layer ad-hoc. As a result, nothing is reused — we don't get the nicely-layered abstraction that the OSI model suggests we should, and I reimplement a COBS encoder / decoder, message buffering, etc. in pretty much every embedded project I work on. Partially that's my problem for not standardizing my own work, but I'm also pointing a finger at the embedded world for not having any networking standards outside of microcontrollers with wireless stacks — I'm generally pretty good about using nice things when they exist.</p> <p>To some extent, this problem is a function of working in the embedded world. There's a tendency to see the embedded environment as categorically different from programming with an OS available. This makes sense if your first thought when you hear the word "embedded" is a PIC-8 — I can't afford a networking stack when I'm working with at most 4KB RAM.</p> <p>However, we now live in a world where you can easily get megabytes of both flash and RAM on low-cost (&lt; $10) MCUs — that's enough to store the entire disk and process image of a regular OS executable without stripping or size optimization. We can afford to have some nice things.</p> <p>In particular, I would like to have a networking stack that <em>works</em> with regular IP — you know, what the internet is made of. And when I say "works", I don't mean supports-being-a-leaf in the way that all the wireless networking stacks do. Rather, I mean I want to implement a routed, PHY-agnostic IP <em>network</em>. For IP to work as-designed, you need to be able to route packets.</p> <h3 id="aside-storage-cost">aside: storage cost</h3> <p>I write most of my firmware in Rust, which has many of the nice bells and whistles you'd expect in an OS environment as libraries. This costs memory (on the order of hundreds of KiB flash, dozens of KiB RAM), but even so, I'm typically not space-constrained.</p> <p>If storage space is a concern though, <a href="https://www.mouser.com/c/semiconductors/memory-ics/?interface%20type=SPI">flash</a> and <a href="https://www.adafruit.com/product/4677">RAM</a> are cheap — if it's going to make firmware development easier, I lean heavily towards just adding more space to the board, even at the shocking cost of a whole additional couple dollars.</p> <h2 id="goal">goal</h2> <p>I want to be able to power on an MCU and have it automatically advertise itself as an IP-capable <em>router</em> over all communication interfaces:</p> <ul> <li>USB: CDC-NCM, optionally CDC-ACM as serial-ppp</li> <li>UART, I2C, SPI, CAN: ppp</li> <li>WiFi: native</li> <li>Bluetooth, LoRa, Thread: 6LoWPAN / native Thread</li> </ul> <p>By <em>router</em> I mean it should support:</p> <ul> <li>iBGP</li> <li>MLD / IGMP</li> <li>ICMP{,v6}</li> <li>ARP / NDP (as necessary -- most of these are point-to-point)</li> <li>IP{,v6}</li> </ul> <h3 id="update-4-4-24-routing">update (4/4/24): routing</h3> <p>I was thinking about proposing some version of this project for an <a href="https://nlnet.nl/">nlnet</a> grant and so have been reading more on prior art. There are really two components to the project: the generic network-interface implementation and bridging and routing. There is <em>extensive</em> prior art on the routing side that I was no more than peripherally aware of. The term of art for this problem is MANET (mobile ad-hoc network), and routing implementations differ in a few dimensions — most notably between reactive and proactive paradigms, and in node-local state overhead. For my use-case, a proactive routing algorithm that does not require global network knowledge is ideal, as I value both low latency and a minimal memory footprint.</p> <p>I have considered both <a href="https://datatracker.ietf.org/doc/html/draft-wunderlich-openmesh-manet-routing-00">BATMAN</a> and <a href="https://datatracker.ietf.org/doc/html/rfc8966#name-introduction">Babel</a> in some depth.</p> <p>BATMAN(-advanced) operates at layer 2 and has an in-tree Linux kernel implementation. Its goal as described in its draft RFC is to discover the best next-hop for each route, rather than computing the route in its entirety. I'm hopeful that this means that memory overhead can be kept small, in accordance with the goal of operating on embedded microcontrollers.</p> <p>Babel was interesting mostly because it has a reference implementation that isn't tied to the Linux kernel and states that it has a low code-size. It's a hybrid MANET implementation that seems (by reputation) to be fairly efficient, has nice loop-avoidance capabilities, and is designed to respond favorably during reconvergence events.</p> <p>Based on the RFCs, BATMAN appears more suited to my needs and easier to implement, so I intend to port it to Rust, then expose an Arduino interface to the Rust library.</p> <h3 id="meshing">meshing</h3> <p>The system should support automatic, provisioning-free/zero-configuration meshing. That is, every device that can see any other device should connect to it and route packets for it.</p> <p>In order to efficiently make use of routing tables, the network should ideally converge to an addressing scheme that divides subnets based on locality and connectivity. Graph regions with low diameter should be seen as candidates for subnet division — what we want is for this graph:</p> <pre class="z-code"><code><span class="z-text z-plain">A - B - C </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> D </span><span class="z-text z-plain"> | </span><span class="z-text z-plain">E - F - G </span></code></pre> <p>to "understand" that the addresses for A, B, C should be in one subnet, and E, F, G should be in another, so that D can serve as an edge router between them.</p> <p>To rephrase the problem in the converse sense, if we randomly assign addresses, we should expect a high degree of fragmentation in the routing tables. In the limiting / pathological case, every node's routing table contains the whole network topology — the benefit of dynamic destination routing vanishes. So we need some spatial organization of the node addressing.</p> <p>I suspect such an addressing scheme can be achieved with a locally-greedy algorithm, but the price we pay is that existing node addresses may change when new nodes are added to the network. We can address this algorithmically and mitigate the impact by having old addressing information survive network reorganization for a limited period of time.</p> <h2 id="prior-art">prior art</h2> <ul> <li> <p>Zephyr</p> <ul> <li>Has a <a href="https://docs.zephyrproject.org/latest/connectivity/networking/api/net_l2.html#net-l2-interface">nice model</a> for abstracting the L2 networking interface and allowing pluggable implementations. I don't use zephyr, but it's compelling and a great model for portability for OS concepts onto embedded platforms.</li> <li>Has <a href="https://docs.zephyrproject.org/2.7.5/reference/kconfig/CONFIG_NET_ROUTING.html"><code>CONFIG_NET_ROUTING</code></a>, which unfortunately appears to be unused ("something would have to populate the routing table" — doesn't give me confidence that it's stable/definitely working)</li> </ul> </li> <li> <p>Rust</p> <ul> <li><a href="https://github.com/smoltcp-rs/smoltcp"><code>smoltcp</code></a>: <code>no_std</code>-compatible userspace networking stack (name misleading -- not just TCP!)</li> <li><a href="https://github.com/rust-embedded-community/embedded-nal"><code>embedded-nal</code>, <code>embedded-nal-async</code></a>: <code>no_std</code>-compatible interface traits</li> <li><a href="https://github.com/embassy-rs/embassy/tree/main/embassy-net"><code>embassy-net</code></a> and associated drivers: <code>no_std</code> networking stack built on top of <code>smoltcp</code>, intended for use within the <code>embassy</code> project <ul> <li>Associated drivers include <code>embassy-net-ppp</code>, which runs a networking link over</li> </ul> </li> </ul> </li> <li> <p>Meshing</p> <ul> <li><a href="https://www.open-mesh.org/projects/batman-adv/wiki">batman-adv</a></li> <li><a href="https://www.bluetooth.com/learn-about-bluetooth/feature-enhancements/mesh/">bluetooth mesh</a></li> <li><a href="https://en.wikipedia.org/wiki/Thread_(network_protocol)">Thread</a></li> <li><a href="https://meshtastic.org/">meshtastic</a></li> </ul> </li> </ul> <h2 id="plan-project-components">plan / project components</h2> <ul> <li> <p>Meshing experiments in simulation</p> <ul> <li>Candidate meshing implementation -- develop addressing algorithm</li> <li>Simulate a bunch of agents connecting, disconnecting</li> <li>Measure network throughput, packet loss, etc.</li> </ul> </li> <li> <p>IP transport over multiple PHYs</p> <ul> <li>Currently planning to use <code>embassy-net-ppp</code></li> <li>Validate functionality across multiple PHYs <ul> <li>Highest priority: SPI, UART, I2C</li> <li>CAN if possible</li> </ul> </li> </ul> </li> <li> <p>Router implementation</p> <ul> <li>Rust library to act as an IP router — own multiple smoltcp interfaces, route packets across them</li> </ul> </li> </ul> 2024-03-14T00:00:00+00:00 2024-03-14T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/maxl-unreliable/ <p>Jake published a paper called <a href="https://cba.mit.edu/docs/papers/23.10.MAXL-Motion.pdf">MAXL</a>, which is a distributed/networked machine controller that does time sync and manages trajectory buffers.</p> <p>As I wrote about <a href="../ip-embedded">here</a>, I'm working on meshing + IP routing on embedded. The short version is that I want this because it's compatible with, you know, the internet — essentially everything, from anywhere. Security, obviously, would be a huge concern with exposing this to the internet, and it would need to be locked down before doing so. But you <em>could</em>, and more relevantly, IP allows arbitrary network topologies, up to limitations of your link budget. It would make it very easily, comparatively, to plug in a new actuator, rearrange cables, etc.</p> <p>The apparent problem with doing this is that dynamically destination-routed packets in an unreliable network may never arrive, and if we're using them for machine control, that seems bad — MAXL depends on realtime network qualities that an IP network (that hides the PHY layer) totally trashes. My answer to this problem is to make the MAXL system CAM- and kinematics-aware, in order to ensure that in the worst case, the machine pauses briefly in a safe location while waiting for new packets.</p> <h2 id="trajectory-plannning">trajectory plannning</h2> <p>How? As part of the CAM process, partition your tool trajectories into those with tool engagement and those without. Plunge -&gt; side-mill -&gt; retract might be a trajectory with engagement, and a rapid above the plane of the part is an example of one without.</p> <p>(For simplicity we'll treat rapids in-plane as engaged moves as actuators require some, but potentially not precise, synchronization — we can cut corners here to optimize, but that can come later.)</p> <p>If you're going to execute an engaged trajectory (using this plunge -&gt; side-mill -&gt; retract as our example), you make sure all motors can execute it <em>atomically</em> before committing to execution. That is, the whole trajectory must be loaded into memory on all distributed actuators, and you only command execution of this one safe trajectory at a time. Now if you let the machine run, it will do one safe thing — it will end in the retracted state, not engaged with the part.</p> <p>If the command is disengaged, then you can execute the command without waiting for global synchronization from all motors.</p> <p>In general, as long as you can ensure that all actuators have loaded or executed all programs <em>up to the end</em> of a given engaged trajectory in the program, you can queue execution of that trajectory. This means that you can keep loading trajectory data as long as the motor has available memory, and queue execution as all other actuators report readiness.</p> <p>These assumptions mean that we don't need a realtime network. If we only execute when it's safe, and end up in a safe place, then we can</p> <h3 id="estop">estop</h3> <p>In order to avoid Byzantine problems, I'm assuming an estop is in the machine reachable by the controller, and I treat it as an absolutely-reliable communication channel. (For robustness to Byzantine faults we can say it has watchdog timer functionality, so network partitions mean estop.) This solves the problem of the controller telling the motors to start, but only wanting them all to start if they're <em>all</em> ready. But establishing that requires another roundtrip, which the motors may also not acknowledge, etc. etc.</p> <p>Instead, send the "go" as normal, and if any motors don't acknowledge within a window, trigger estop — this doesn't sacrifice functionality for us, as this is definitely a failure condition for a distributed machine.</p> <h3 id="safe-tails-leaders">safe tails + leaders</h3> <p>What happens if our atomic trajectories are too long to fit in memory? The scheme relies on this being possible. As-required, compute "safe tails" for too-long atomic trajectories (power off spindle, raise Z), etc. and inject them into the program in order to create synthetic safe points (you'll need to create safe lead-ins as well that undo the tail operation). This has the effect of producing new atomic subtrajectories — you intentionally size these to fit into memory on your actuators.</p> <p>In the normal case, you're aiming not to execute these — you try to load the whole next segment, acquire global actuator acknowledgement, and cancel the next tail/leader pair before the distributed machine starts to run it.</p> <p>If required though, if the machine is stuck waiting for new data, the result is that it automatically goes to a safe spot to wait.</p> 2024-03-14T00:00:00+00:00 2024-03-21T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/molybdos/ <p><em>batteries-included, arduino-inspired library for easy rust embedded bringup</em></p> <p><a href="https://public.git.npry.dev/molybdos">https://public.git.npry.dev/molybdos</a></p> <p>I want more people to use Rust on embedded. It's a great language, it has a package manager, the library support is great, and it encourages people to write better, clearer, more correct code, while not reinventing the wheel.</p> <h2 id="current-shortcomings-improvement-areas">current shortcomings / improvement areas</h2> <p>Unfortunately, the story for Rust on embedded currently involves a lot of boilerplate and pitfalls. Once you have your environment set up properly, it's great, but for instance:</p> <ul> <li>Common, quasi-standard library needs to be re-added to every project <ul> <li><code>heapless</code></li> <li><code>embassy_*</code></li> <li><code>embedded_*</code></li> <li><code>defmt</code></li> <li><code>panic_*</code></li> <li><code>cortex_m{,_rt}</code> / <code>riscv{,_rt}</code></li> <li>etc.</li> </ul> </li> <li>Common build scripts need to be added to every project</li> <li>Shared features (<code>defmt</code>/<code>log</code>, <code>alloc</code>, <code>serde</code>, <code>default_features = false</code>) are tedious to add to every project</li> <li>Often need to write a linker file for your chip</li> <li>Some libraries use weak linking for dependency management — they need linker definitions added in each project</li> <li>Boilerplate peripheral bringup is kind of annoying to write <ul> <li>E.g. no USB-CDC by default (typical Arduino <code>Serial</code> implementation)</li> <li>Pins are unique type-level handles to register values. This provides type-safety but means you can't access them generically (e.g. put them into an array) without <code>.downgrade()</code>ing them individually</li> </ul> </li> <li><code>embedded_*</code> interfaces use AFIT (async-function-in-trait) rather than a polling interface, making them not easily compatible with e.g. <code>futures::{Stream, Sink}</code></li> <li>No-op imports for lang items:</li> </ul> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-keyword z-other z-rust">use</span> panic_abort <span class="z-keyword z-operator z-rust">as</span> <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-keyword z-other z-rust">use</span> defmt_rtt <span class="z-keyword z-operator z-rust">as</span> <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p>All of this is pretty straightforwardly mitigated by writing a library crate, which is what I'm working on.</p> <h2 id="progress">progress</h2> <h3 id="linker-file-generation">linker file generation</h3> <p>One of the first tasks I'm tackling is a linker file generator that runs at build-time. Intended interface:</p> <pre data-lang="toml" class="language-toml z-code"><code class="language-toml" data-lang="toml"><span class="z-source z-toml"><span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> Cargo.toml</span> </span><span class="z-source z-toml"> </span><span class="z-source z-toml"><span class="z-punctuation z-definition z-table z-begin z-toml">[</span><span class="z-meta z-tag z-table z-toml"><span class="z-entity z-name z-table z-toml">dependencies</span></span><span class="z-punctuation z-definition z-table z-end z-toml">]</span> </span><span class="z-source z-toml"><span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">molybdos</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-punctuation z-definition z-inline-table z-begin z-toml">{</span> <span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">version</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>...<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span><span class="z-punctuation z-separator z-inline-table z-toml">,</span> <span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">features</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-punctuation z-definition z-array z-begin z-toml">[</span><span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>linker_gen<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span><span class="z-punctuation z-definition z-array z-end z-toml">]</span> <span class="z-punctuation z-definition z-inline-table z-end z-toml">}</span> </span></code></pre> <p>This will cause a <code>molybdos</code>' <code>build.rs</code> to generate a linker file (<a href="https://github.com/embassy-rs/embassy/blob/main/examples/nrf51/memory.x">e.g.</a>) for the selected chip and emit the typical Cargo instructions (example below from <a href="https://github.com/embassy-rs/embassy/blob/ee1aa80e3063de35a6f68c918a18b506d7f49539/examples/nrf51/build.rs#L19-L34">here</a> (nRF51*, but meaningfully the same for at least most Cortex-M MCUs with <code>defmt</code> enabled)):</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> out <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-keyword z-operator z-bitwise z-rust">&amp;</span><span class="z-meta z-path z-rust">PathBuf<span class="z-punctuation z-accessor z-rust">::</span></span>from<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-path z-rust">env<span class="z-punctuation z-accessor z-rust">::</span></span>var_os<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>OUT_DIR<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unwrap</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-meta z-path z-rust">File<span class="z-punctuation z-accessor z-rust">::</span></span>create<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>out<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">join</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>memory.x<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-source z-rust"> <span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unwrap</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-source z-rust"> <span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">write_all</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-support z-macro z-rust">include_bytes!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>memory.x<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-source z-rust"> <span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">unwrap</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo:rustc-link-search=<span class="z-constant z-other z-placeholder z-rust">{}</span><span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-separator z-rust">,</span> out<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">display</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo:rerun-if-changed=memory.x<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo:rustc-link-arg-bins=--nmagic<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo:rustc-link-arg-bins=-Tlink.x<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-support z-macro z-rust">println!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>cargo:rustc-link-arg-bins=-Tdefmt.x<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></code></pre> <p>This task is still in-progress.</p> <h3 id="peripheral-bringup">peripheral bringup</h3> <h4 id="ontology">ontology</h4> <p>The embedded ontology de-facto settled upon by Rust embedded projects is very generic:</p> <ul> <li>A <strong>p</strong>eripheral <strong>a</strong>ccess <strong>c</strong>rate (aka "pac", <a href="https://github.com/nrf-rs/nrf-pacs/blob/90977499146de8444579538e7ad2466d1d9823db/pacs/nrf52833-pac/src/lib.rs">e.g. for nRF52833</a>) is written (usually generated using <a href="https://github.com/rust-embedded/svd2rust"><code>svd2rust</code></a>). This is a register-level interface to the MCU.</li> <li>A <strong>h</strong>ardware <strong>a</strong>bstraction <strong>l</strong>ayer (aka "hal", <a href="https://github.com/embassy-rs/embassy/blob/ee1aa80e3063de35a6f68c918a18b506d7f49539/embassy-nrf/src/lib.rs">e.g. for nRF</a>) is (usually hand-) written that wraps the pac and makes it ergonomic to use — this usually means adapting it to Rust embedded conventions and interfaces. The pac will contain your SPI control register definition and access, the hal will make it look like an <code>embedded_hal_async::spi::SpiBus</code>. <ul> <li>A common convention in hals is providing a <code>Peripherals</code> struct that contains unique handles to the pac registers. On startup, you run an <code>init</code> function exactly once to receive a <code>Peripherals</code> instance, and then destructure it into relevant fields that you can use to construct the hal types you need. E.g.:</li> </ul> </li> </ul> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Pull in the HAL GPIO types. </span></span><span class="z-source z-rust"><span class="z-keyword z-other z-rust">use</span> <span class="z-meta z-path z-rust">embassy_nrf<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">gpio<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-keyword z-operator z-arithmetic z-rust">*</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> p<span class="z-punctuation z-separator z-rust">:</span> <span class="z-meta z-path z-rust">embassy_nrf<span class="z-punctuation z-accessor z-rust">::</span></span>Peripherals <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">embassy_nrf<span class="z-punctuation z-accessor z-rust">::</span></span>init<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-support z-type z-rust">Default</span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>default<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Construct a new HAL gpio::Output type (which has e.g. </span></span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Output::{set_high, set_low, toggle}) </span></span><span class="z-source z-rust"><span class="z-storage z-type z-rust">let</span> <span class="z-storage z-modifier z-rust">mut</span> led <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">Output<span class="z-punctuation z-accessor z-rust">::</span></span>new<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> gpio::Output requires a handle to a pin, which we can only </span></span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> get from an embassy_nrf::Peripherals </span></span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> p<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-constant z-other z-rust">P0_13</span><span class="z-punctuation z-separator z-rust">,</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> <span class="z-meta z-path z-rust">Level<span class="z-punctuation z-accessor z-rust">::</span></span>Low<span class="z-punctuation z-separator z-rust">,</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"> <span class="z-meta z-path z-rust">OutputDrive<span class="z-punctuation z-accessor z-rust">::</span></span>Standard<span class="z-punctuation z-separator z-rust">,</span> </span></span><span class="z-source z-rust"><span class="z-meta z-group z-rust"></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> SPI buses, I2C, USB, timers, ADCs, etc. are all constructed </span></span><span class="z-source z-rust"><span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> following a similar pattern. </span></span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-keyword z-control z-rust">loop</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> led<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">toggle</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">Timer<span class="z-punctuation z-accessor z-rust">::</span></span>after_millis<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-constant z-numeric z-integer z-decimal z-rust">300</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span>await<span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></code></pre> <ul> <li>Interface crates are a level higher and what the hals are written against, and typically only contain trait definitions and common helper functions. They exist as common definitions to decouple dependencies and improve compatibility. (Examples: <code>embedded_hal{,_async}</code>, <code>embedded_io{,_async}</code>, <code>embedded_nal{,_async}</code>, etc., which provide bus definitions, an embedded version of <code>io::{Read, Write, Seek}</code>, network interfaces, and more)</li> <li>Bus peripheral drivers and applications are ideally written on top of the interface crates for portability, compatibility, and decoupling. E.g. the <a href="https://docs.rs/sx127x_lora/latest/sx127x_lora/"><code>sx127x</code></a> LoRa radio driver is written against the generic <code>embedded_hal::spi::SpiBus</code> definition and can run on anything that can provide one (including Linux! as their examples point out — there is an <a href="https://github.com/rust-embedded/linux-embedded-hal"><code>embedded_hal</code> interface</a> for Linux userspace).</li> </ul> <p>While this stack is well-designed and great to use once you understand it, it can take quite a while to understand how it wants to be used and configured. It also requires repetitive setup of the same things, when across most projects you just want a quick, low-overhead way to e.g. get access to the SPI bus.</p> <h4 id="hiding-the-stack">hiding the stack</h4> <p>By contrast to the above, Arduino doesn't tell us anything about the abstraction stack or require us to configure it beyond selecting our board. Your interface to Arduino as a user is <code>Wire</code>, <code>Serial</code>, <code>SPI</code>, <code>{analog,digital}{Write,Read}</code>, etc. I want to make it similarly easy to access Rust peripherals without requiring this explicit understanding or direct bringup of the stack.</p> <p>However, I want to strike a good balance re: not going too far in the Arduino direction and making assumptions willy-nilly. A nice interface looks like this to me:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-meta z-annotation z-rust"><span class="z-punctuation z-definition z-annotation z-rust">#</span><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-variable z-annotation z-rust">molybdos</span>::<span class="z-variable z-annotation z-rust">main</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span> </span><span class="z-source z-rust">async <span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">main</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"> <span class="z-storage z-modifier z-rust">mut</span> <span class="z-variable z-parameter z-rust">m</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-meta z-path z-rust">molybdos<span class="z-punctuation z-accessor z-rust">::</span></span>Molybdos, </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-path z-rust">molybdos<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">molybdos<span class="z-punctuation z-accessor z-rust">::</span></span>info<span class="z-keyword z-operator z-logical z-rust">!</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>started up<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> spi <span class="z-keyword z-operator z-assignment z-rust">=</span> m<span class="z-punctuation z-accessor z-dot z-rust">.</span>spi<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-constant z-numeric z-integer z-decimal z-rust">0</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">init</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-path z-rust">molybdos<span class="z-punctuation z-accessor z-rust">::</span></span>SPIConfig <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> mosi<span class="z-punctuation z-separator z-rust">:</span> <span class="z-constant z-numeric z-integer z-decimal z-rust">1</span><span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> miso<span class="z-punctuation z-separator z-rust">:</span> <span class="z-constant z-numeric z-integer z-decimal z-rust">2</span><span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> sck<span class="z-punctuation z-separator z-rust">:</span> <span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>P0.12<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">pin</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-separator z-rust">,</span> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> Supported by a trait -- molybdos::PinLookup. </span></span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> cs<span class="z-punctuation z-separator z-rust">:</span> <span class="z-constant z-numeric z-integer z-decimal z-rust">4</span><span class="z-punctuation z-separator z-rust">,</span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-operator z-range z-rust">..</span><span class="z-support z-type z-rust">Default</span><span class="z-meta z-path z-rust"><span class="z-punctuation z-accessor z-rust">::</span></span>default<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-group z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> peripheral lookup by string name -- could support BSPs as well as IC pinout names </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> m<span class="z-punctuation z-accessor z-dot z-rust">.</span>gpio<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">named</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>P0.13<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">toggle</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> resolve pin name to id to avoid repeated lookup </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> pin_id <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">molybdos<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">platform<span class="z-punctuation z-accessor z-rust">::</span></span>lookup_pin<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>P0.13<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> m<span class="z-punctuation z-accessor z-dot z-rust">.</span>gpio<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span>pin_id<span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">toggle</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> &quot;take&quot; a pin from the molybdos::Molybdos instance to reserve it exclusively. </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> When exclusive handle is dropped, becomes available to take again. </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> <span class="z-storage z-modifier z-rust">mut</span> pin <span class="z-keyword z-operator z-assignment z-rust">=</span> m<span class="z-punctuation z-accessor z-dot z-rust">.</span>gpio<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">take</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>pin_id</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-keyword z-operator z-rust">?</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">into_output</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-meta z-path z-rust">Level<span class="z-punctuation z-accessor z-rust">::</span></span>Low<span class="z-punctuation z-separator z-rust">,</span> <span class="z-meta z-path z-rust">DriveStrength<span class="z-punctuation z-accessor z-rust">::</span></span>Standard</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> pin<span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">set_high</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-keyword z-control z-rust">loop</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> numeric indexing if already known </span></span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> m<span class="z-punctuation z-accessor z-dot z-rust">.</span>gpio<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-constant z-numeric z-integer z-decimal z-rust">1</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">toggle</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-meta z-path z-rust">embassy_time<span class="z-punctuation z-accessor z-rust">::</span></span><span class="z-meta z-path z-rust">Timer<span class="z-punctuation z-accessor z-rust">::</span></span>after_millis<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-constant z-numeric z-integer z-decimal z-rust">300</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span>await<span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p>This interface implies type-erased peripherals — I want to present peripherals with duplicates uniformly rather than specialized to their pac type as the normal Rust stack does.</p> <p>The configuration interface I'm aiming for would be as follows:</p> <pre data-lang="toml" class="language-toml z-code"><code class="language-toml" data-lang="toml"><span class="z-source z-toml"><span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> Cargo.toml</span> </span><span class="z-source z-toml"> </span><span class="z-source z-toml"><span class="z-punctuation z-definition z-table z-begin z-toml">[</span><span class="z-meta z-tag z-table z-toml"><span class="z-entity z-name z-table z-toml">dependencies</span></span><span class="z-punctuation z-definition z-table z-end z-toml">]</span> </span><span class="z-source z-toml"><span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">molybdos</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-punctuation z-definition z-inline-table z-begin z-toml">{</span> <span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">version</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>...<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span><span class="z-punctuation z-separator z-inline-table z-toml">,</span> <span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">features</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-punctuation z-definition z-array z-begin z-toml">[</span><span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>nrf52833<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span><span class="z-punctuation z-definition z-array z-end z-toml">]</span> <span class="z-punctuation z-definition z-inline-table z-end z-toml">}</span> <span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> only need to specify MCU</span> </span></code></pre> <p>Still working on this — focusing on developing the nRF platform to completion currently.</p> <h2 id="aside-curse-of-abstraction-zero-cost-abstraction">aside: curse of abstraction / zero-cost abstraction</h2> <p>There's a "curse of abstraction" in many programming environments, where people accept abstractions having a cost / this is in the culture and basic assumptions. But if every library has a 2% cost to your expressive capability, and your transitive dependency graph has 50 libraries in it, all of a sudden you have 36% of your original capabilities (assuming that 2% is multiplicative, which it probably isn't), because everything's making tiny "probably true" assumptions for "convenience", not all of which are actually true, but you're stuck with them unless you actually fork the repo, go read the datasheet in detail to make the thing do what you want, and basically redo all the work you were trying to avoid by using a library. Ask me how I know.</p> <p>One of Rust's mantras, borrowed from C++ with some additional flavor, is that of zero-cost abstraction: if you don't use it, it doesn't cost you. Illustratively, Java does not have zero-cost abstractions. You pay for the hundreds of megabytes of runtime loading on every process startup. If you want to run a program to add two integers and print the result, the whole GC still loads, the whole class loading mechanism, etc. But if you run a {Rust, C, C++} program, it just runs and does exactly what you want. The <code>class</code> mechanism in C++ is relatively minimal and doesn't depend on any runtime components, as a specific example. An enhancement of the zero-cost principle is that even abstractions that you <em>do</em> use shouldn't impose any additional cost over hand-writing the concretized version yourself. This is what Rust aims for. See the Godbolt embedded below for an example — in Rust, functional combinators <em>are equivalent to for loops</em> after compiler optimization.</p> <iframe width="1000px" height="600px" src="https://godbolt.org/e#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:rust,selection:(endColumn:40,endLineNumber:21,positionColumn:40,positionLineNumber:21,selectionStartColumn:40,selectionStartLineNumber:21,startColumn:40,startLineNumber:21),source:'%23%5Bno_mangle%5D%0A%23%5Binline(never)%5D%0Apub+fn+sum_of_squares_loop(nums:+%26%5Bi32%5D)+-%3E+i32+%7B%0A++++let+mut+sum+%3D+0%3B%0A%0A++++for+num+in+nums+%7B%0A++++++++sum+%2B%3D+num+*+num%0A++++%7D%0A%0A++++sum%0A%7D%0A%0A%23%5Bno_mangle%5D%0A%23%5Binline(never)%5D%0Apub+fn+sum_of_squares(nums:+%26%5Bi32%5D)+-%3E+i32+%7B%0A++++nums.into_iter().map(%7Cn%7C+n+*+n).sum()%0A%7D%0A%0A%0Apub+fn+main()+%7B%0A++++let+x+%3D+sum_of_squares(%26%5B1,+2,+3,+4%5D)%3B%0A++++let+y+%3D+sum_of_squares_loop(%26%5B1,+2,+3,+4%5D)%3B%0A++++println!!(%22%7Bx%7D+%7By%7D%22)%3B%0A%7D'),l:'5',n:'0',o:'Rust+source+%231',t:'0')),k:50,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((g:!((h:compiler,i:(compiler:r1640,filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:1,lang:rust,libs:!(),options:'-C+opt-level%3D3+-C+no-vectorize-loops',overrides:!(),selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:'5',n:'0',o:'+rustc+1.64.0+(Editor+%231)',t:'0')),k:50,l:'4',m:50,n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compilerName:'rustc+1.64.0',editorid:1,fontScale:14,fontUsePx:'0',j:1,wrap:'1'),l:'5',n:'0',o:'Output+of+rustc+1.64.0+(Compiler+%231)',t:'0')),header:(),l:'4',m:50,n:'0',o:'',s:0,t:'0')),k:50,l:'3',n:'0',o:'',t:'0')),l:'2',n:'0',o:'',t:'0')),version:4"></iframe> <p>(Had to disable loop autovectorization to make the equivalence legible.)</p> <p>You'll notice that there's only one function in the disassembly, <code>sum_of_squares</code>. The compiler optimized the combinator loop to the exact same assembly as the for loop. (On a newer Rust compiler, it was actually able to unroll the combinator loop (and not the for loop), so I had to roll it back to an older version to get this result.)</p> <p>In this spirit, having all the knobs available is absolutely, 100% the right thing for the embedded ecosystem in Rust to have done. None of the libraries make assumptions for you, at least not that you can't reconfigure. However, we want to end up with high-level wrapper libraries that <em>do</em> make those assumptions for you — they can let you get started quickly, and you can sub them out for the lower- level interfaces as needed. Rust doesn't currently have these, and that's what I'm aiming to write.</p> <h2 id="etymology-molubdos">etymology: μόλυβδος</h2> <p>μόλυβδος (<em>molybdos</em>) is Greek for lead. "Batteries-included" -&gt; lead-acid batteries -&gt; lead. I just like the word (and the evident but unexpected connection to molybdenum).</p> 2024-03-14T00:00:00+00:00 2024-03-21T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/mudlrs/ <p><a href="https://public.git.npry.dev/molybdos">https://public.git.npry.dev/molybdos</a></p> <p>This is a work-in-progress port of <a href="https://github.com/jakeread/mudlink">Jake's MUDL library</a> to <a href="https://rust-lang.org">Rust</a>.</p> <pre data-lang="toml" class="language-toml z-code"><code class="language-toml" data-lang="toml"><span class="z-source z-toml"><span class="z-comment z-line z-number-sign z-toml"><span class="z-punctuation z-definition z-comment z-toml">#</span> Cargo.toml</span> </span><span class="z-source z-toml"><span class="z-punctuation z-definition z-table z-begin z-toml">[</span><span class="z-meta z-tag z-table z-toml"><span class="z-entity z-name z-table z-toml">dependencies</span></span><span class="z-punctuation z-definition z-table z-end z-toml">]</span> </span><span class="z-source z-toml"><span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">mudl</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-punctuation z-definition z-inline-table z-begin z-toml">{</span> <span class="z-meta z-tag z-key z-toml"><span class="z-entity z-name z-tag z-toml">git</span></span> <span class="z-punctuation z-definition z-key-value z-toml">=</span> <span class="z-string z-quoted z-double z-basic z-toml"><span class="z-punctuation z-definition z-string z-begin z-toml">&quot;</span>https://public.git.npry.dev/molybdos<span class="z-punctuation z-definition z-string z-end z-toml">&quot;</span></span> <span class="z-punctuation z-definition z-inline-table z-end z-toml">}</span> </span></code></pre> <h2 id="rust-codec">rust: <code>Codec</code></h2> <p>There are multiple versions of a generic <code>codec</code> concept in Rust crates:</p> <ul> <li><a href="https://docs.rs/tokio-util/latest/tokio_util/codec/index.html"><code>tokio_util::codec</code></a> (<a href="https://tokio.rs/">tokio</a>-specific)</li> <li><a href="https://docs.rs/asynchronous-codec/latest/asynchronous_codec/"><code>asynchronous_codec</code></a></li> <li><a href="https://github.com/matthunz/futures-codec"><code>futures_codec</code></a> (defunct)</li> </ul> <p>The concept interacts with Rust's <code>Stream</code> and <code>Sink</code> types, which represent sources and sinks (respectively) of values, which may be unbounded in length and can be iterated or submitted to asynchronously.</p> <p>A <code>Decoder&lt;T&gt;</code> implementation wraps an <code>io::AsyncRead</code> and converts it to a <code>Stream&lt;T&gt;</code>. An <code>Encoder&lt;T&gt;</code> wraps an <code>io::AsyncWrite</code> and converts it to a <code>Sink&lt;T&gt;</code>.</p> <p>Concretely, we might have <code>Decoder&lt;serde_json::Json&gt;</code> which decodes bytes into the generic json inductive type, or <code>Encoder&lt;String&gt;</code>, a trivial <code>Encoder</code> that encodes strings as (for instance) utf-8 bytes.</p> <p>This is the abstraction I would like to use for my implementation of <code>mudl</code>, as it's extremely generic and abstracts exactly the concept I'm aiming for. Unfortunately, existing implementations of this type depend on rust's full stanadard library, which isn't generally available on embedded targets.</p> <h2 id="week-of-3-14-2024">Week of 3/14/2024</h2> <p>I forked and began rewriting <code>asynchronous_codec</code> to support <code>embedded-io-async</code>'s <code>Read</code> and <code>Write</code> traits instead of <code>AsyncRead</code> and <code>AsyncWrite</code> (standard-library-dependent traits) — you can see this in the repo. Unfortunately, the signatures for <code>Stream</code> and <code>Sink</code> aren't readily compatible with the embedded traits' <code>read</code> and <code>write</code> methods. I haven't decided yet if I'm going to adapt them to one another or write a specialized <code>embedded_codec</code> crate instead.</p> <h2 id="week-of-3-21-2024">Week of 3/21/2024</h2> <p>This week I realized <code>mudl</code>'s approach doesn't agree with my needs, so I decided to diverge from it.</p> <p>The project I'm writing now (to be renamed) has the same goals (establishing a plug-and-play link over Serial), but uses FEC rather than checksumming and has packet segmentation + reassembly built-in.</p> <p>I'm using Reed-Solomon as an ECC and COBS still for delimiting frames.</p> <p>The message encoding stack is as follows:</p> <pre class="z-code"><code><span class="z-text z-plain">| Original data | </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> COBS Encode </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> </span><span class="z-text z-plain">| COBS | COBS | COBS | COBS | 0 | </span><span class="z-text z-plain"> |____________ </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> Reed-Solomon </span><span class="z-text z-plain"> (each frame) </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> </span><span class="z-text z-plain">| COBS | Parity | (one frame) </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> </span><span class="z-text z-plain"> COBS Encode </span><span class="z-text z-plain"> | </span><span class="z-text z-plain"> v </span><span class="z-text z-plain"> </span><span class="z-text z-plain">| COBS | 0 | </span></code></pre> <p>I.e. we split the original packet into COBS subpackets (can be done iteratively), calculate Reed-Solomon for each subpacket, then COBS encode that. This gives a natural way to do segmentation while only requiring a single subframe in memory at any time (applications may choose to fully reassemble) the complete original frame if desired, but this is not required for the protocol to work.</p> <p>The double-COBS wrapping is an attempt to mitigate corruptions of the sentinel.</p> <p>The Reed-Solomon ECC overhead can be tuned based on the physical link characteristics to mitigate packet corruption or loss without stateful negotiation or a control channel in the protocol.</p> <p>I'm still in the middle of implementing this.</p> 2024-03-01T00:00:00+00:00 2024-03-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/heat-press/ <p><strong>NOTE</strong>: This project is relatively expensive for the course budget (~$350 / person) and isn't strictly necessary for my system, so I'm not including it as a component I'm committing to.</p> <p>A heat press for flattening or forming small pieces of sheet stock.</p> <h2 id="specifications">specifications</h2> <p>(subject to adjustment)</p> <ul> <li> <p>Stock dimensions &lt;= 200mm x 200mm x 10mm, must be rectilinear</p> </li> <li> <p>Conveyor or roller feed in/out in a north-south direction</p> </li> <li> <p>50C &lt; Max temperature &lt; 100C</p> </li> <li> <p>1N &lt; Max closing force &lt; 10N</p> </li> <li> <p>Package dimensions: &lt;= 250mm x 250mm x 250mm</p> </li> <li> <p>DIN rail mountable</p> </li> <li> <p>M4 machine screw mounting holes in corners</p> </li> <li> <p>Power interface: 12V, 5A barrel jack</p> </li> </ul> <h3 id="heat-forming-dies">heat forming dies</h3> <p>Machine is configurable with low-relief heat-forming dies &lt; 50mm x 50mm.</p> <ul> <li>Low-pressure only! Not for stamping or punching unless very malleable material</li> <li>Must be sufficiently heat-conductive</li> <li>Die holder geometry TBD -- currently envisioning a replaceable section of the heating plates</li> </ul> <h3 id="communication-interface">communication interface</h3> <ul> <li>Speaks <a href="https://protobuf.dev">Protobuf</a> (<a href="../misc/protobuf">plug</a>) over UART</li> <li>12-pin IDC connector (<a href="../misc/pinout">candidate standardized pinout</a>)</li> <li>Digital pin control (preconfigured temperature, closing height, feed distance) <ul> <li>In <ul> <li>Feed / Not Stop</li> <li>Close / Not Open</li> <li>Heat / Not Cool</li> </ul> </li> <li>Out <ul> <li>Overheat</li> <li>Motion complete</li> <li>General fault</li> </ul> </li> </ul> </li> </ul> <h3 id="cost-complexity">cost/complexity</h3> <ul> <li>On the order of $100 in parts, most COTS, some 3d printed, PCB</li> <li>Assembly time: an afternoon</li> </ul> <h2 id="work-in-progress-bom">work-in-progress BoM</h2> <ul> <li> <p>$32 <a href="https://www.digikey.com/en/products/detail/sparkfun-electronics/COM-11288/6569360">resistive heaters x 8</a></p> </li> <li> <p>$20 <a href="https://www.mcmaster.com/products/shafts/linear-motion-shafts-5/">shafts (~10mm?)</a></p> </li> <li> <p>$10 <a href="https://www.mcmaster.com/products/bushings/plain-bearings~/oil-embedded-sleeve-bearings-7/system-of-measurement~metric/">bushings</a></p> </li> <li> <p>$15 <a href="https://www.mcmaster.com/products/springs/compression-springs-7/system-of-measurement~metric/id~10-6-mm/">springs</a></p> </li> <li> <p>OR: $10 <a href="https://www.amazon.com/dp/B08B4JDB67">v rollers</a></p> </li> <li> <p>$30? 8020 frame + assembly hardware</p> </li> <li> <p>$5 3d prints</p> </li> <li> <p>$10 electrical components</p> </li> <li> <p>$15 <a href="https://www.amazon.com/dp/B08JPM29FD">lead screw x2</a></p> </li> <li> <p>$12 <a href="https://www.amazon.com/dp/B00PNEQ9T4">NEMA 12 stepper</a></p> </li> <li> <p>$9 <a href="https://www.amazon.com/dp/B07BRKZGMS">GT2 Belt</a></p> </li> <li> <p>$7 <a href="https://www.amazon.com/dp/B077GNZK3J">GT2 Pulleys</a></p> </li> </ul> <p>Total ~$150 at current estimate.</p> 2024-03-01T00:00:00+00:00 2024-03-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/pcb-system/ <p><a href="../clank-build">update: clank build</a></p> <p><a href="../casette">update: casette build</a></p> <script type="module" src="https://ajax.googleapis.com/ajax/libs/model-viewer/3.1.1/model-viewer.min.js"></script> <p>Desktop-scale PCB maker that completes a 2-layer board in under an hour.</p> <h2 id="state-of-the-world-why">state of the world / why</h2> <ul> <li>PCBs from China are cheap and fast (JLC, PCBWay) <ul> <li>Still too slow for iterating effectively</li> </ul> </li> <li>PCBs from the US are expensive and slow, but required sometimes for export control</li> <li>DIY options have major drawbacks <ul> <li>Approaches <ul> <li>Mill</li> <li>Lasercut</li> <li>Chemical etch</li> <li>Print conductive ink</li> </ul> </li> <li>&lt; 1 day turnaround, but at the cost of babysitting and obtuse tooling</li> <li>Low quality <ul> <li>Process variability</li> <li>Resolution limits</li> </ul> </li> <li>Process limitations: <ul> <li>2-layer is difficult, &gt; 2 infeasible</li> <li>Masking is difficult</li> <li>Silks are difficult</li> </ul> </li> </ul> </li> </ul> <p>The product I want can take a KiCad project and produce a consistent board (with mask, no assembly) within the hour without supervision.</p> <h2 id="requirements">requirements</h2> <ul> <li>At least 200um trace width</li> <li>2 layers</li> <li>(Nice-to-have) selectively applies solder mask</li> <li>(Nice-to-have) conductive vias</li> <li>If milling <ul> <li>Mesh bed leveling</li> <li>Automatic tool changer</li> </ul> </li> </ul> <h2 id="design-draft">design draft</h2> <p><model-viewer src="blockout.glb" shadow-intensity="1" camera-controls touch-action="pan-y" style="width: 900px; height: 600px;"></model-viewer></p> <p>Currently planning on using most recent revision of <a href="https://clank.tools">Clank</a> (stretch variant) as the platform.</p> <p>Additional features:</p> <ul> <li> <p>Vacuum holddown</p> </li> <li> <p>Toolchanger</p> <ul> <li>Isolation: V-bit</li> <li>Cutout: endmill</li> </ul> </li> <li> <p>Stock loading and manipulation (ER arm)</p> </li> </ul> <h3 id="anticipated-flow">anticipated flow</h3> <ul> <li> <p>Upload KiCad board file to website hosted by rpi attached to clank</p> <ul> <li><a href="https://docs.kicad.org/8.0/en/cli/cli.html">Export gerbers</a></li> <li>Run <a href="https://modsproject.org/">mods</a> or <a href="https://github.com/pcb2gcode/pcb2gcode">pcb2gcode</a> as CAM -&gt; GCode</li> <li>Auto-tabs (require at least 2)</li> </ul> </li> <li> <p>GCode translation / edits as required -- working with Jake</p> <ul> <li>Trying MAXL</li> <li>Fallback: <a href="https://github.com/grbl/grbl">GRBL</a> or similar on a COTS controller + motor driver board</li> </ul> </li> <li> <p>Stock handling</p> <ul> <li> <p>Goals:</p> <ul> <li>Load sheets from stack of stock, index to consistent position</li> <li>Flip stock for second side of board, reindex <em>stock outline</em> to same position</li> </ul> </li> <li> <p>Want to use <a href="https://www.elephantrobotics.com/en/mycobot-en/">ER mycobot arm</a> with suction cups (vacuum)</p> <ul> <li>Probably need to reserve some real-estate on the stock for clean pickup points</li> </ul> </li> <li> <p>Open-loop stock indexing: pins, push into corner</p> </li> <li> <p>Indexing side 2</p> <ul> <li>Cutouts for X-Y probing?</li> <li>Could do CV, but not really a fan. Maybe the right thing to do here though.</li> <li>Maybe just measure width of stock, compute where board should be, fix x zero</li> </ul> </li> <li> <p>Outfeed to stack by machine</p> </li> </ul> </li> <li> <p>Vacuum holddown</p> <ul> <li>Just a plate with hole pattern and a plenum underneath. Use a shop vac with a relay.</li> <li>Selected because it seems most straightforward way to automatically control holddown</li> </ul> </li> <li> <p>Autoleveling</p> <ul> <li>Probe with Clank's load cell</li> </ul> </li> <li> <p>Machining sequence</p> <ul> <li>V-bit isolation (front)</li> <li>Flip</li> <li>V-bit isolation (back)</li> <li>Cutout</li> </ul> </li> <li> <p>Tool changing</p> <ul> <li>Use "fork" design suggested by Jake</li> <li>Interpose a holdable U slot shape in the Kleat interface stackup</li> <li>Several forks mounted to the bed</li> <li>Lower the U of the tool onto the fork, release the Kleat, pull back</li> <li>Inverse for pickup</li> </ul> </li> </ul> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;u_holder.e8be58ed48e82c1b.jpg"> </div> <p><model-viewer src="u_holder.glb" shadow-intensity="1" camera-controls touch-action="pan-y" style="width: 900px; height: 600px;"></model-viewer></p> <h3 id="solder-mask">Solder mask</h3> <p>Not in first rev of the machine. If the two-sided milling works, will add.</p> <p>Concept:</p> <ul> <li>squeegee liquid mask through screen for consistent application amount</li> <li>cure with UV light mounted to machine or on tool head</li> <li>selectively mill off with <a href="https://www.youtube.com/watch?v=wr7l67sd3NM">springloaded v-bit</a></li> </ul> <p>Sequencing: after isolation on each layer.</p> <h3 id="vias">Vias</h3> <p>Not in first rev of the machine. If the two-sided milling works, will add.</p> <p>Concept:</p> <ul> <li>rivets</li> <li>anvil / die at a fixed location mounted to bed</li> <li>cobot picks up and holds stock, referencing gerbers or pcb file (** cobot probably insufficient for precision)</li> <li>custom end effector with a rivet magazine and punch</li> </ul> <p>Sequencing: after both sides isolated, before cutout.</p> 2024-03-01T00:00:00+00:00 2024-03-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/machines/stock-elevator/ <p>An elevator for feeding stacked sheet stock sheet-by-sheet.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sketch.e2363a6f2c434628.jpg"> </div> <h2 id="specifications">specifications</h2> <p>(subject to adjustment)</p> <ul> <li> <p>Accepts vertical 100mm stack of stock</p> </li> <li> <p>Dimensional tolerance across stackup +- 2mm in XY</p> </li> <li> <p>Stock dimensions &lt;= 200mm x 200mm x 10mm, must be rectilinear</p> </li> <li> <p>Outfeed at the top of the stack, height TBD</p> </li> <li> <p>Package dimensions: &lt;= 250mm x 250mm x 250mm</p> </li> <li> <p>DIN rail mountable</p> </li> <li> <p>M4 machine screw mounting holes in corners</p> </li> <li> <p>Power interface: 12V, 5A barrel jack</p> </li> </ul> <h3 id="communication-interface">communication interface</h3> <ul> <li> <p>Speaks <a href="https://protobuf.dev">Protobuf</a> (<a href="../misc/protobuf">plug</a>) over UART, 115200 baud</p> </li> <li> <p>12-pin IDC connector (<a href="../misc/pinout">candidate standardized pinout</a>)</p> </li> <li> <p>Digital pin control (preconfigured temperature, closing height, feed distance)</p> <ul> <li>In <ul> <li>Feed once (edge triggered)</li> </ul> </li> <li>Out <ul> <li>Feeding</li> <li>Out of stock</li> <li>General fault</li> </ul> </li> </ul> </li> </ul> <h3 id="cost-complexity">cost/complexity</h3> <ul> <li>On the order of $100 in parts, most COTS, some 3d printed, PCB</li> <li>Assembly time: an afternoon</li> </ul> <h2 id="work-in-progress-bom">work-in-progress BoM</h2> <ul> <li> <p>$20 <a href="https://www.mcmaster.com/products/shafts/linear-motion-shafts-5/">shafts (~10mm?)</a></p> </li> <li> <p>$10 <a href="https://www.mcmaster.com/products/bushings/plain-bearings~/oil-embedded-sleeve-bearings-7/system-of-measurement~metric/">bushings</a></p> </li> <li> <p>OR: $10 <a href="https://www.amazon.com/dp/B08B4JDB67">v rollers</a> with 8020</p> </li> <li> <p>$30? 8020 frame + assembly hardware</p> </li> <li> <p>$10 3d prints</p> </li> <li> <p>$10 electrical components</p> </li> <li> <p>$15 <a href="https://www.amazon.com/dp/B08JPM29FD">lead screw x2</a></p> </li> <li> <p>$12 <a href="https://www.amazon.com/dp/B00PNEQ9T4">NEMA 12 stepper</a></p> </li> <li> <p>$9 <a href="https://www.amazon.com/dp/B07BRKZGMS">GT2 Belt</a></p> </li> <li> <p>$7 <a href="https://www.amazon.com/dp/B077GNZK3J">GT2 Pulleys</a></p> </li> </ul> 2023-12-29T00:00:00+00:00 2024-08-12T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/edf/ <div style="display: flex; flex-direction: column; align-items: center; padding: 1rem" class="vidwrap"> <video src="tvc_drone.webm" muted controls class="hover_controls" style="width: 480px; border-radius: 1rem" > </video> <i style="margin-top: 0.5rem"> <p>inspiration (<a href="https://youtube.com/watch?v=u2cETOyuJ20">youtube</a>, <a href="https://www.printables.com/model/722967-ducted-fan-thrust-vectoring-drone">docs</a>)</p> </i> </div> <p>I've been into controls for a year or so and thought this would be a great project to experiment with. I should be able to (literally) get it off the ground for design validation using <a href="https://docs.px4.io/main/en/">PX4</a> — they use it in this video, just running PID. I have a flight controller to use from work on <a href="../omnidrone">omnicopter</a>.</p> <p>I'm aiming to implement LQR with an observer from scratch running on a microcontroller, then bring in more advanced approaches in <a href="https://underactuated.mit.edu">underactuated robotics</a> (I was a listener in Spring 2024).</p> <h2 id="progress">progress</h2> <p>I've been iterating on mechanical for a long time, more or less whenever I've had a spare moment in the past 6 months. Many many revisions of the nacelle, mostly to work out fitment and assembly around the servo mounting and control vanes.</p> <p>I'm currently dealing with an apparent mismatch on the nacelle and vane dimensions — the vane shaft is too long to the point it collides with the servo. It looks wrong, but the measurements I've taken all line up with the CAD, which doesn't look wrong and suggests the servo should fit. I've had other things to do for a few weeks so have just left it in this state for now.</p> 2023-12-19T00:00:00+00:00 2023-12-19T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/final-tracking/ <script type="module" src="https://ajax.googleapis.com/ajax/libs/model-viewer/3.1.1/model-viewer.min.js"></script> <p><video src='final_video.mp4' type="video/mp4" loop muted autoplay style="width: 600px"></video></p> <p><strong>vr cockpit simulator</strong></p> <ul> <li> <p><em>welded steel frame</em></p> </li> <li> <p><em>adjustable chair</em></p> </li> <li> <p><em>mfd button bezel</em></p> </li> <li> <p><em>mfd test interface</em></p> </li> </ul> <p><a href="https://blog.npry.dev/class/htm/final-tracking/mfd_controller.ino">mfd controller arduino sketch</a></p> <p><a href="https://blog.npry.dev/class/htm/final-tracking/mfd.tar.gz">mfd design files</a></p> <p><a href="https://blog.npry.dev/class/htm/final-tracking/mfd_test_interface.tar.gz">mfd interface</a></p> <p><a href="https://blog.npry.dev/class/htm/final-tracking/chair.step">chair + frame design files (STEP)</a></p> <p><a href="https://blog.npry.dev/class/htm/final-tracking/final_slide.pdf">summary slide</a></p> <p>Seat model viewer:</p> <p><model-viewer src="chair.glb" shadow-intensity="1" camera-controls touch-action="pan-y" style="width: 640px; height: 480px;"></model-viewer></p> <p>MFD model viewer:</p> <p><model-viewer src="mfd.gltf" shadow-intensity="1" camera-controls touch-action="pan-y" style="width: 640px; height: 480px;"></model-viewer></p> <p><em>Early render (previous revision):</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chair.486ad0f7036396cb.jpg"> </div> <p>I built a flight simulator cockpit designed for VR. It integrates:</p> <ul> <li>Position-adjustable mounts for components I had prior to the class (flight stick, throttle, rudder pedals)</li> <li>Multi-function display ("MFD") button bezels that present to the host computer as 25-button gamepads over USB</li> <li>A highly position-adjustable seat, supporting independently setting: <ul> <li>The height of the front of the seat</li> <li>The height of the back of the seat</li> <li>Seat back angle</li> </ul> </li> <li>A test interface for the MFDs</li> </ul> <p>Problems I'm solving:</p> <ul> <li>Setup and teardown cost of my existing peripherals is high (attaching/detaching to desk and putting back into storage). I want a fixed, desk-independent setup where everything is in position by default.</li> <li>Using rudder pedals for an extended period of time in a normal chair causes you to lean back on your tailbone. Not ergonomic over any meaningful amount of time -- chair is adjustable to allow me to find a reasonably comfortable sitting position.</li> <li>For similar reasons, control manipulator (throttle, rudder pedals, joystick) position is important relative to sitting position -- these should be finely adjustable.</li> <li>VR-controller-based cockpit interaction is very clunky. I want physical buttons instead, where possible. MFDs are the clearest pain point -- I use them a lot to interact with menuing, and they're impractical to bind to existing surplus buttons.</li> </ul> <h2 id="prior-art">prior art</h2> <p>There is extensive prior art in building simulated cockpits online. A conceptual inspiration for me is <a href="https://thewarthogproject.com/">The Warthog Project</a>, building a simulator for an A-10C II Warthog, who I've watched extensively on YouTube.</p> <p>Worth also putting in this section that I already had my primary flight controls before even starting the class and had desk mounts for them.</p> <h2 id="production-summary-bom">production summary + bom</h2> <h3 id="seat">seat</h3> <ul> <li>MIG welded steel tube (1.25" OD x 0.125" wall thickness, ~30' from CBA shop stock)</li> <li>FDM-printed bearing and interface blocks (PLA, produced on ResEnv Prusas and my personal Ender 3)</li> <li>1/2-13 threaded rod (<a href="https://www.amazon.com/dp/B07N91CGYB">Amazon</a>, $13 per 2), with <a href="https://www.amazon.com/dp/B009EE2SN0">nuts</a> and <a href="https://www.amazon.com/dp/B009OJI0XC">washers</a></li> <li>M8 and 5/16" (nearly the same OD, so functionally interchangeable in my project) bolts, nuts, and washers (various lengths, some from <a href="https://www.amazon.com/dp/B01C3KUGVC">Amazon</a>, some from Home Depot)</li> <li>8mm ground shaft -- <a href="https://www.amazon.com/dp/B01NCOMFLT">Amazon</a></li> <li>Skateboard bearings (8mm x 22mm x 7mm) -- <a href="https://www.amazon.com/dp/B08XVFSZTF">Amazon</a></li> <li>Latex foam matress topper (seat, unknown provenance -- received for free)</li> <li>3/4" plywood (seat, unknown provenance -- received for free)</li> </ul> <h3 id="flight-controls-i-already-owned-all-from-virpil-controls">flight controls (i already owned, all from <a href="https://virpil-controls.us.com/">virpil controls</a>)</h3> <ul> <li><a href="https://virpil-controls.us.com/vpc-mongoost-50cm2-grip.html">MongoosT-50CM2 Grip</a></li> <li><a href="https://virpil-controls.us.com/vpc-mongoost-50cm3-base.html">MongoosT-50CM3 Stick Base</a></li> <li><a href="https://virpil-controls.us.com/vpc-flightstick-extension-200mm.html">VPC Flightstick Extension (200mm)</a></li> <li><a href="https://virpil-controls.us.com/vpc-mongoost-50cm3-throttle.html">MongoosT-50CM3 Throttle</a></li> <li><a href="https://virpil-controls.us.com/vpc-ace-flight-pedals.html">VPC ACE Pedals</a></li> </ul> <h3 id="mfd-panel">mfd panel</h3> <ul> <li>22ga sheet steel (cold-rolled), lasercut and hemmed in CBA shop (see <a href="../wildcard/">wildcard week</a>)</li> <li>FR1 copper boards, double-sided (<a href="https://www.sparkfun.com/products/14979">SparkFun</a>) -- milled on ResEnv PCB mill with 20 deg v-bits</li> <li>FDM-printed MFD frame (PLA, ResEnv Prusas)</li> <li>M4 heat-set inserts and machine screws (from ResEnv inventory)</li> <li>12mm momentary buttons (from ResEnv inventory)</li> <li>SLA-printed button heads (ResEnv Form 3, Clear V4 resin)</li> </ul> <h3 id="software">software</h3> <ul> <li>Autodesk Inventor (CAD)</li> <li>OnShape (CAD, switched from Inventor)</li> <li>KiCad (EDA)</li> <li>Blender (misc renders)</li> <li>Arduino (controller firmware)</li> <li>pygame (test interface)</li> </ul> <h2 id="mfds">mfds</h2> <p><em>Early concept:</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd.0104aa52284938d5.jpg"> </div> <h3 id="summary">Summary</h3> <p>"Multi-function display" -- displays in cockpit with buttons around them that a pilot can press for various menued functions. Since I fly in VR, I don't need the display element itself, just the buttons.</p> <p>I designed the MFD in 4 modular parts that fit together with dovetails. Each side mounts a PCB:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;board_fit.b3bb8345cf8cae58.jpg"> </div> <p>and has 5 buttons:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;boards_inplace.538db757baa31aa4.jpg"> </div> <p>The boards interface with IDC connectors which are connected to a controller board. The controller is a RasPi Pico that reads the digital state of all of its pins and connects to a host computer over USB as a generic gamepad.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;controller_assembled.a48fe03e55dfc3f9.jpg"> </div> <h3 id="v1-button-boards-frame">v1 (button boards + frame)</h3> <h4 id="dovetails">dovetails</h4> <p>I started by printing a test piece for the corner dovetails (zero offset made a nice tight fit):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;corner_test.8b92d54e593c1be3.jpg"> </div> <p>With heatsets installed and M3 screws:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;corner_test_heatset.b2ec8eb6edccdd54.jpg"> </div> <p>First version with full sides (wrong size, mitered corners):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;full_edges.e695d8ac03a224ce.jpg"> </div> <h4 id="button-assembly">button assembly</h4> <p>I printed heads for 12mm pushbuttons using the Form 3 out of clear resin:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;button_heads.7c00852b139ccba0.jpg"> </div> <p>Assmbled:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;button_assembled.f858b52edb4d8d37.jpg"> </div> <p>Zero offset was also just right for these.</p> <h4 id="pcb">pcb</h4> <p>I transfered the relevant outline from Inventor and designed the boards to fit within the available space. I marked mounting holes where the heatsets would be.</p> <p>I did some test patterns because I was seeing axis-aligned inconsistency in my cuts:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;test_patterns.f1363de62bf22d09.jpg"> </div> <p>First try was a bit fuzzy:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milling_burrs.0346a171eb73ee23.jpg"> </div> <p>Some more attempts:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milling_attempts.1fde8412bc44b7bb.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milling_attempts_2.f6856b59ab721064.jpg"> </div> <p>Finally a successful board:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milled_board_ok_inplace.cc708e0bcbbaa978.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milled_board_ok.487eadbfeed894b8.jpg"> </div> <h3 id="buttons-final">buttons (final)</h3> <p>The board needed a minor rev after I updated the layout of the controller board to change the order of the pinout. I also increased trace width and isolation to make the boards easier to mill and solder:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;buttons_inplace.002118d8f0ac4617.jpg"> </div> <p>To get the buttons in the right spot, I placed them in the frame upside-down and put a dot of superglue onto each one:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;superglue_applied.e68849e6e947eae3.jpg"> </div> <p>Then I screwed the pcb into the frame and let the superglue dry. I took the whole assembly out once it was dry and had the buttons in exactly the right place:</p> <p>Then I soldered them:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;buttons_soldered.2a50b6a8b30897c7.jpg"> </div> <p>I discovered eventually that all of the boards always reported button 1 pressed. This was because of this mounting hole (rightmost):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;short.852d15bd1c4f37f4.jpg"> </div> <p>The threaded insert would short the ground plane to the trace next to the hole, making it look like the right button was always pressed. So I applied superglue as conformal coating:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;conformal.6aed17c65c47a4ef.jpg"> </div> <p>This worked.</p> <h3 id="controller">controller</h3> <p>Milled controller board:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd_controller_milled.c8e077d6152d0eda.jpg"> </div> <p>Cleaned up:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd_controller_milled2.9c76bc82fbd94dec.jpg"> </div> <p>Forgot to individually isolate pads on pico reverse, so as in the button boards, applied superglue as conformal coating:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;superglue_rp2040.8f23775e59ae0c82.jpg"> </div> <p>Pico soldered:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;soldered_rp2040.e9895601c70a779d.jpg"> </div> <p>Assembled with IDC connectors:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;controller_assembled.a48fe03e55dfc3f9.jpg"> </div> <p>You'll note I'm using 2-layer boards with through-hole components -- as I described in <a href="../elec-production/">electronics production</a>, I used a small drill bit (~3mm OD) by hand to chamfer / countersink the holes on the reverse side of the board so the pins wouldn't make contact. If you're deliberate about it, this approach is very consistent in ensuring the pins don't short to the back plane.</p> <h3 id="firmware">firmware</h3> <p>Uses the rp2040 port of the Arduino <code>Joystick</code> library to represent the mfd as a gamepad. Very simple -- polling-based. Slight optimization I made that drastically improves responsiveness is setting manual reporting and doing change tracking myself — naive approach sends a USB packet for every button it scans.</p> <p>Sketch <a href="https://blog.npry.dev/class/htm/final-tracking/mfd_controller.ino">here</a>.</p> <h3 id="interface">interface</h3> <p>I made <a href="https://blog.npry.dev/class/htm/final-tracking/mfd_test_interface.tar.gz">an interface</a> in pygame to validate the function of the MFD controllers.</p> <p>This is functionally duplicative of the Windows gamepad tester -- I really only made this to fulfill the requirement that I personally implement the interface.</p> <p>Plugging and unplugging a controller:</p> <p><video src='plug_unplug.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Shorting a button gpio to ground (emulating button press):</p> <p><video src='basic_demo.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>MFDs are hotpluggable and multiple are supported simultaneously:</p> <p><video src='second_mfd.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <h3 id="controller-enclosure">controller enclosure</h3> <p>I 3d-printed an enclosure for the controller out of PLA:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pcb_enclosure.50620401fffa00fb.jpg"> </div> <p>Cable routing (reverse):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pcb_enclosure_wiring.86c1451d91a8b978.jpg"> </div> <h2 id="frame">frame</h2> <p>I made the frame out of 1 1/4" OD x 1/8" wall round pipe. I cut the pieces I need on the horizontal bandsaw:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;bandsaw.6a47c59220041daa.jpg"> </div> <p>Result:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pieces_cut.a39acde521e41b38.jpg"> </div> <p>I chamfered them on the belt sander:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;belt_sander.9b8eb2fcec12ca51.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chamfered.d9acc422ed47f3f0.jpg"> </div> <p>And used an angle grinder with a flap disk to clean the scale off the surfaces to prepare for welding:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;angle_grinder.928c2e94c0d4410a.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weld_cleaned.fd242ae270985a2e.jpg"> </div> <p>I milled cutouts on several of the T-joints to improve fitment:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milling_corner.3b97f46fe3d1ab68.jpg"> </div> <p>I needed through-holes in several parts, which I did on the drill press.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;thru_holes_center.0bd2095e51ea2220.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;thru_holes.84999f1b6bd1c022.jpg"> </div> <p>I didn't do a great job controlling weld heat, so the T-joints on the upright warped the frame upwards. I added feet made out of scrap to level the piece:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;welded_feet.c8a24fbba42104be.jpg"> </div> <h3 id="mfd-front-panel">mfd front panel</h3> <p>I stiffened the front panel I made in <a href="../wildcard/">wildcard week</a> using MIG welding and some small square tube:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;stiffened_welds.c189022df8fc7494.jpg"> </div> <p>Obviously, it's not perfect -- nowhere close to rigid -- but I was able to take most of the warp out of it that I put into it from hammering the hem.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;stiffened_panel.8bc97a4e84f720fd.jpg"> </div> <h2 id="chair-joints">chair joints</h2> <p>The joints are 3d printed and have bearings pressed into them that ride on 8mm shaft.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;3dprints_assembled.af457f8a1953ecbd.jpg"> </div> <p>The chair legs are height-adjustable via nuts on threaded rod.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;nut_interface.c1202820ca35aa93.jpg"> </div> <p>The top of the threaded rod is captured by a clevis block with a bearing that allows the connected part of the chair to move vertically:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;joint.647bc09e0f78f1df.jpg"> </div> <p>Together, these blocks permit fore-and-aft vertical adjustment of the seat base and angular adjustment of the seat back.</p> <h2 id="controls-mounting">controls mounting</h2> <p>The controls mount with custom blocks that friction fit (tightly) onto the tube — adjusting the position of the controls means wiggling them on the tube they're mounted on.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;panel_mount.ccfee0ea576f06aa.jpg"> </div> <p>This is the rudder mount being printed:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;printing_rudder_mount.5188649d99da2635.jpg"> </div> <p>It is the one mount that needs to be tapped in with a hammer because there's so much contact area.</p> <h2 id="problems">problems</h2> <h3 id="racking">racking</h3> <p><video src='frame/frame_racking.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>The clevis joints on the frame are nowhere near sturdy enough to resist racking laterally — I could tell they were going to snap. So I sacrificed a couple of degrees of freedom and welded the front of the chair in place. This made the chair sturdy enough, but still left me the back screws to adjust.</p> <h3 id="3d-printing">3d printing</h3> <h4 id="broken-heater">broken heater</h4> <p>I mostly used Responsive Environments' fdm printers for my 3d printing needs. On one of them, the wires fatigued off of the heating element because the heater block wasn't screwed into the heat brake tightly:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;hotend_broken.be771cdd67967ba6.jpg"> </div> <p><a href="https://fab.cba.mit.edu/classes/863.10/people/brian.mayton/index.html">Brian</a> and I fixed this up with spare parts he brought from home.</p> <h4 id="clevis-split">clevis split</h4> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;split_clevis.bcdb979d57bba180.jpg"> </div> <p>These clevis blocks were printed in a convenient-but-weak orientation and split when I pressed bearings into them.</p> <h2 id="how-evaluated">how evaluated</h2> <p>The project's internal evaluation norms are whether I'm comfortable in the seat and if it's sufficiently adjustable to put my body where it needs to be to use the controls, but the adjustability shouldn't permit it to move if I'm not adjusting it. I also needed it to be minimally portable (I need to be able to move it in my car).</p> <p>The project succeeds on the comfort and portability axes — I built it for everything to come off of the frame, so it will fit in my car. The latex foam makes it very comfortable.</p> <p>It's not perfectly stable — I didn't handle lateral stability well. I'm considering fine-tuning the position and then welding the back legs of the chair in place to make it fully rigid.</p> <p>It doesn't entirely succeed on the adjustability axis either — I was able to get pretty close to what I want, but I put the uprights for the front panel slightly in the way of where my legs want to be to use the rudder pedals, and the joystick is too far forward (I may be able to fix this with more padding on the seat back).</p> <h2 id="implications">implications</h2> <p>There are minimal procedural or research implications from the work — this was instead primarily a fabrication project and learning experience for me. Personally, the learnings are to simplify more aggressively, and intend + plan to iterate more.</p> 2023-12-13T00:00:00+00:00 2023-12-13T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/wildcard/ <p><a href="https://cad.onshape.com/documents/5dc9365a8ee70304f1b05067/w/76d905231d4bc180fafdc1a7/e/34fe706dffdfdb7ae7433d47">onshape design</a></p> <p><a href="https://blog.npry.dev/class/htm/wildcard/wildcard-step-files.tar.gz">step files</a></p> <p><a href="https://blog.npry.dev/class/htm/wildcard/wildcard-dxfs.tar.gz">dxfs</a></p> <h2 id="requirements">requirements</h2> <ul> <li>design, cut, and assemble a sheet metal part <ul> <li>the design should include at least one hem or bend</li> <li>and should require spot welding to assemble</li> </ul> </li> </ul> <h2 id="summary">summary</h2> <p>I designed the front panel for my final project that will hold the two mfds.</p> <h2 id="v1">v1</h2> <p>I made my design in OnShape and only exported a <em>face</em> as dxf to import into the laser software the first time.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_inlaser_v1.09da6905a5bcaf99.jpg"> </div> <p>Since I only exported the face, the design was missing all of the material for the bends.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_v1.6dbaf28f009dc475.jpg"> </div> <h2 id="v2">v2</h2> <p>Successfully unfolded the sheet metal design as dxf and exported.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_inlaser_v2.ae618b105b3ae498.jpg"> </div> <p>Hemmed, bent, and spot-welded together:</p> <p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_spot_welded_bottom.c4056e7c1d913c5c.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_spot_welded_top.4e82d085efc17116.jpg"> </div> </p> <p>With the mfd outline in place:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutout_with_panel.3cc68c26fb8372d5.jpg"> </div> <h2 id="welding">welding</h2> <p>I spent most of a day self-teaching welding on both mig and tig.</p> <h3 id="mig">mig</h3> <p>Some miscellaneous experiments out of scrap:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;misc_experiments_1.0994b94a9d31a3ff.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;misc_experiments_2.0d883424e14f71eb.jpg"> </div> <p>Real attempts at nicer joints:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;butt_joint.f2fb73435042f1a9.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;round_tube.d010a54c3d669a4d.jpg"> </div> <h3 id="scraper">scraper</h3> <p>I tried to make a scraper to clean the welding spatter off of the table out of scrap:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;scraper.ce5865c781de1e37.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;scraper_2.363f9b01ad17c645.jpg"> </div> <p>But the spatter is very hard, and my scraper was mild steel, so the edge mostly just deformed:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;scraper_edge.a72a4564ee32fad8.jpg"> </div> <h3 id="tig">tig</h3> <p>There was some warp in my panel and I wanted to take it out by welding stiffeners to it. I figured I'd need to use tig to do this -- I practiced on scrap 22ga:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;tig_experiments.c2a5a84f3978e83f.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;tig_experiments_p2.9fcb129493bd83fc.jpg"> </div> 2023-12-06T00:00:00+00:00 2023-12-06T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/mechanical/ <p><a href="https://blog.npry.dev/class/htm/mechanical/bridge.tar.gz">serial-nats bridge</a></p> <p><a href="https://blog.npry.dev/class/htm/mechanical/COBSNATS.ts">modular things nats client</a></p> <p><a href="https://blog.npry.dev/class/htm/mechanical/install.sh">raspi setup script</a></p> <p><a href="https://fab.cba.mit.edu/classes/863.23/CBA/machine/">cba section site</a></p> <p><a href="https://gitlab.cba.mit.edu/classes/863.23/CBA/machine">section repo</a></p> <p>We built a machine for producing video clips of a subject simultaneously from multiple angles, and compositing these clips into a single video (set to music).</p> <h2 id="remote-modular-things">remote modular things</h2> <p><em>system diagram (2 concepts)</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;system_diagram.791c041ea8aa2261.jpg"> </div> <p>I wrote a bridge that enables you to centrally control modular things plugged into many different devices from a single instance of the web interface.</p> <p><video src='bridge_demo.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>The bridge is a python script that you run on as many devices as you want. It talks to a message broker (<a href="https://nats.io">NATS</a>). When you plug modular things into a device with the bridge running, the bridge discovers the serial connection, announces it on the broker, subscribes to a <code>write</code> topic for the thing, and publishes any data sent by the thing to a <code>read</code> topic.</p> <p>I adapted a version of the WebSerial connector in the modular-things frontend to connect to the message broker instead of WebSerial and automatically discover devices. You can then use the frontend as normal.</p> <p>Unfortunately, we're not using this bridge in the live system because I ran out of time to debug some issues (discussed below).</p> <h3 id="why-this-approach">why this approach</h3> <p>The point of this was to get rid of some wires. Currently, all of the modular things need to be plugged into the single computer running the frontend because they have to talk over webserial. This is annoying, and we have raspis on each of the systems anyway to talk to the cameras, so I wanted to just move the usb cables onto the raspis instead.</p> <h4 id="socat"><code>socat</code></h4> <p>Originally, I wanted to use <code>socat</code> as a point-to-point bridge over TCP. Something like:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> remote (with modular things plugged in)</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> socat<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>d</span> /dev/ttyACM0,raw,echo=0 TCP-LISTEN:0.0.0.0:1234</span> </span><span class="z-source z-shell z-bash"> </span><span class="z-source z-shell z-bash"><span class="z-comment z-line z-number-sign z-shell"><span class="z-punctuation z-definition z-comment z-begin z-shell">#</span></span><span class="z-comment z-line z-number-sign z-shell"> on host running modular things frontend</span><span class="z-comment z-line z-number-sign z-shell"> </span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> socat<span class="z-variable z-parameter z-option z-shell"><span class="z-punctuation z-definition z-parameter z-shell"> -</span>d</span> TCP:remote:1234 PTY,link=/dev/ttyV1,raw,crnl</span> </span></code></pre> <p>I was hoping that Chrome would connect to <code>/dev/ttyV1</code> on the second host, but it seems that the webserial implementation will <em>only</em> connect to devices that the host kernel identifies as having serial drivers, so this doesn't work.</p> <h3 id="issues">issues</h3> <p>I got the bridge implementation working with a single servo board initially, only really testing the discovery mechanism by plugging and unplugging the thing, and verifying that it showed up and disappeared from the frontend when I did that, without throwing errors in js or python. Discovery requires bidirectional packet transfer between the thing and the frontend, so I figured this would be a good place to start.</p> <p>This worked fine, but when I added more serial ports, I ran into problems. Specifically, the python bridge started throwing exceptions when more than one serial port was connected in quick succession (e.g. because a USB hub with with multiple things was plugged in). I was pretty sure I had written the bridge in a way that precluded race conditions (the obvious diagnosis for this symptom), but I investigated this and a few other plausible causes.</p> <p>Retrying the serial connection if it fails is eventually what fixed the problem. I figured there was a deeper issue with my code (not releasing an old port properly was the thread I was chasing for a long time), but based on what I saw, I'm guessing that:</p> <ul> <li>The Linux usb serial driver creates the device node for the port immediately when it sees a cdc-acm device on the bus</li> <li>The dev node is created in an 'unready' state, causing the exceptions I was seeing in the Python code</li> <li>There's another configuration step in the driver that occurs after bus discovery, which makes the dev node ready to act as a serial port. This configuration step has some latency and happens serially, port-by-port.</li> </ul> <p>This would explain the behavior and why retries resolve the issue -- a single device won't cause the problem because there's very little latency between the appearance of the device on the bus and the second configuration step, where the dev node is "ready". A bunch of devices at once lead to several of them being unready while devices ahead of them in the queue are configured.</p> <p>All inference made to fit this set of symptoms, so I don't know for sure if it's right, but the fact that connection retry works makes me pretty confident this actually isn't a bug in my code.</p> <h2 id="24v-interface-boards">24v interface boards</h2> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24v_alan.5a220558677fc3c2.jpg"> </div> <p>We wanted the linear axes to move faster than the modular things boards could do with their onboard power supplies. There's an existing design for a 24v power board that would give us this extra speed -- I soldered connectors onto these boards.</p> <p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24v_disasm.9e18c3fc8f5fe19e.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24v_soldered.ee261ce41b19bf7e.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24vx4.917a0c36aae09397.jpg"> </div> </p> <p>Spacers for interposing the 24v boards into the stackup:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24v_spacer.20a8172c5cc472a8.jpg"> </div> <p>Alan 3d printed these spacers and I cleaned them up. This is approximately how they looked stacked up with the modular things boards, though this image has a different spacer part in it:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;24v_stackup.16f89e3a2fcf194a.jpg"> </div> <h2 id="raspi-setup">raspi setup</h2> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;flashing_raspis.9d0443dd00f77c52.jpg"> </div> <p>I helped configure the final raspis. Lancelot reflashed them near the end, and I:</p> <ul> <li>helped him set them up with static IPs</li> <li>set up my laptop as an optional router with NAT to its wifi network <ul> <li>this internet access wasn't required for the final working configuration, but was used for installing dependencies</li> </ul> </li> <li>wrote <a href="https://blog.npry.dev/class/htm/mechanical/install">a simple script</a> to install the basic dependencies</li> </ul> <h3 id="static-ips">static ips</h3> <p>Surprisingly, the static IP configuration had unanticipated problems. I normally only need a static IP on a temporary basis, so I typically go with something like:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ip link set dev ethz up</span> </span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> ip a add xxx.xxx.xxx.xxx/yy dev ethz</span> </span></code></pre> <p>We did this manually to be able to reach them over ssh, then Lancelot made this a systemd unit so they'd have IPs on reboot, but it unfortunately didn't work properly -- two of the three raspis would lose their configuration spontaneously. Most likely the problem was some combination of not having disabled NetworkManager and that if the link ever went down (cable momentarily unplugged), the settings would be lost.</p> <p>So instead, since NetworkManager was running anyway, we used it:</p> <pre data-lang="bash" class="language-bash z-code"><code class="language-bash" data-lang="bash"><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-shell"><span class="z-variable z-function z-shell">$</span></span><span class="z-meta z-function-call z-arguments z-shell"> nmcli con mod ethz <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"> ipv4.addresses xxx.xxx.xxx.xxx/yy <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"> ipv4.gateway www.www.www.www <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"> ipv4.dns 1.1.1.1 <span class="z-punctuation z-separator z-continuation z-line z-shell">\ </span></span></span><span class="z-source z-shell z-bash"><span class="z-meta z-function-call z-arguments z-shell"> ipv4.method manual</span> </span></code></pre> 2023-11-29T00:00:00+00:00 2023-11-29T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/apps-ui/ <p><a href="https://blog.npry.dev/class/htm/apps-ui/main.py">ui script</a></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;ui.884e7f57ac21a455.jpg"> </div> <p>I wrote this one using Python's tkinter bindings. It's a UI for my <a href="../input-devices/">previous</a> <a href="../output-devices/">weeks'</a> Mifare Classic 1K card cloner. Not doing anything special -- just I/O over the text serial port with regex / string matching to determine what the board is doing, and direct serial port writes in response to button clicks.</p> <p>The button functionality mirrors what I describe in the <a href="../output-devices/">output devices</a> section re: modes.</p> <p><video src='ui.webm' type="video/webm" loop muted autoplay style="width: 200px"></video></p> <p>(NB: for logistical filming reasons, these two videos aren't simultaneous. Also note the "write" button not causing a mode change with an empty key is an intentional part of the embedded functionality.)</p> <p><video src='physical_demo.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Another note: it was easier for me at the time to set this up on my breadboard version — it works on the milled board just as well.</p> <h2 id="tkinter">tkinter</h2> <p>I picked tkinter because it's fast and extremely easy to hack something in -- far nicer than web (which requires a whole browser), and built-in to most headed Python distributions.</p> <p>It's very old-fashioned -- everything is mutable state, there's no asynchrony, you drive the event loop manually, and there's no markup language to make design easier, but I really haven't found anything better for rapidly building small, dependency-free<sup class="footnote-reference"><a href="#1">1</a></sup> cross-platform UI with a code size footprint of kilobytes<sup class="footnote-reference"><a href="#2">2</a></sup>.</p> <div class="footnote-definition" id="1"><sup class="footnote-definition-label">1</sup> <p>Up to requiring a tkinter-enabled Python install — obviously it has this runtime dep, but no third-party packages that a user would have to install.</p> </div> <div class="footnote-definition" id="2"><sup class="footnote-definition-label">2</sup> <p>Again, discounting the size of the supporting Python distribution, but even so, this is much much more minimal and resource-efficient than a browser.</p> </div> 2023-11-22T00:00:00+00:00 2023-11-22T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/networking-comms/ <p><a href="https://blog.npry.dev/class/htm/networking-comms/networking-design-files.tar.gz">design files</a></p> <p><a href="https://blog.npry.dev/class/htm/networking-comms/networking-elixir.tar.gz">elixir projects</a></p> <p><em>mcu som</em>: esp32c3 xiao</p> <p><em>erlang vm</em>: <a href="https://www.atomvm.net/">atomvm</a></p> <p>This week is an extension of the <a href="../embedded/">first embedded assignment</a>, in which I functionally completed the networking part of this week's tasks. This week, I designed and built a board to support the Erlang version of the firmware I wrote (which ran on a breadboard previously), and extended the firmware to be able to show new networking functionality for this week.</p> <p><em>Erlang node running</em>:</p> <p><video src='running.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p><em>Boot sequence</em>:</p> <p><video src='bootseq.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Lights in order:</p> <ul> <li>Booted</li> <li>Wifi connected</li> <li>IP acquired</li> <li>NTP sync</li> </ul> <p>The blinking LED runs on an infinite loop independently.</p> <p>The "booted" light can be controlled over UDP using the Erlang client I wrote for the earlier assignment.</p> <h2 id="firmware-improvements">firmware improvements</h2> <p>Beyond designing and milling a board, I added the following improvements to the firmware:</p> <ul> <li> <p>Nonvolatile storage of a well-known remote ip. The device sends a UDP packet to this address with its own IP every time it's assigned one -- the idea is that at some point you store your (hopefully somewhat stable IP) on the device, and it notifies you so you can easily find it without needing to be connected to it.</p> </li> <li> <p>A ping-pong mode -- if you send the node the atom <code>:ping</code>, it responds <code>:pong</code>. Timing with both my laptop and the node on the same WiFi network is bimodal -- half of the packets roundtrip in about 30ms, and the other half take 225ms or so. <strong>This is the fresh networking functionality that I intended to on its own cover this week!</strong></p> </li> </ul> 2023-11-15T00:00:00+00:00 2023-11-15T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/output-devices/ <p><a href="https://blog.npry.dev/class/htm/output-devices/cardcloner.ino">arduino sketch (breadboard pins)</a></p> <p><a href="https://blog.npry.dev/class/htm/output-devices/cardcloner_milled.ino">arduino sketch (milled board pins)</a></p> <p><a href="../input-devices/cardreader-design.tar.gz">board design</a></p> <p>mcu som: rp2040 xiao</p> <p>Reader Module: <a href="https://amazon.com/dp/B07VLDSYRW">HiLetgo RFID Kit</a></p> <p>Test Cards: <a href="https://amazon.com/dp/B0895Y5LGT">LEXI UID PVC Blanks</a></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cardreader_on.d2ea7e567777d6e6.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cardreader_board.f2d04c021c6308dd.jpg"> </div> <p>This week, I upgraded the reader I made <a href="../input-devices/">last week</a>. It now supports cloning the UID of a Mifare Classic 1K card to a new card, wiping the card, and unlocking certain cards for writing. The cloner mode can be changed with the buttons, and the current mode is displayed on the colored LED, as well as over serial.</p> <p>This is an output device in the sense that we're using the reader in a write mode, or from a human interface perspective in the sense that the LED indicates the mode.</p> <p>Colors:</p> <ul> <li>light blue: reader, no key or default key loaded</li> <li>dark blue: reader, non-default key loaded</li> <li>yellow: unlock mode</li> <li>pink: writer mode</li> <li>orange: write default key</li> </ul> <p>Button input scheme (1 to 3, top to bottom respectively):</p> <ul> <li>1: read mode</li> <li>2: unlock mode</li> <li>3: write mode (fails if no key has been read)</li> <li>1 + 2: clear stored key</li> <li>2 + 3: write default key</li> </ul> <p>Milled board (read):</p> <p><video src='../input-devices/cardreader_board.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Milled board (write):</p> <p><video src='cardcloner_board_write.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Milled board (unlock):</p> <p><video src='cardcloner_board_unbrick.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Going through all the operations on the breadboard version:</p> <p><video src='cardreader_demo.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <h2 id="serial-output-event-trace">serial output / event trace</h2> <pre class="z-code"><code><span class="z-text z-plain">read card (sak: 0x08), uid: 0925263e </span><span class="z-text z-plain">[int] mode: write </span><span class="z-text z-plain">overwriting card: 0925263e </span><span class="z-text z-plain">wrote card </span><span class="z-text z-plain">new serial: 0925263e </span><span class="z-text z-plain">[int] mode: unbrick </span><span class="z-text z-plain">unbricked uid sector </span><span class="z-text z-plain">[int] mode: write </span><span class="z-text z-plain">[int] entered write-zero mode </span><span class="z-text z-plain">[int] mode: write </span><span class="z-text z-plain">overwriting card: 01020304 </span><span class="z-text z-plain">wrote card </span><span class="z-text z-plain">new serial: a5a5a5a5 </span><span class="z-text z-plain">[int] mode: write </span><span class="z-text z-plain">[int] erased key </span><span class="z-text z-plain">[int] mode: read </span></code></pre> <h3 id="summary">summary</h3> <ol> <li> <p>Read a card, storing the UID.</p> </li> <li> <p>a. Press the write button, entering write mode</p> <p>b. Present the same card, reading the serial</p> <p>c. Overwrite it with the same serial (no-op, for demo)</p> </li> <li> <p>a. Enter unbrick (unlock) mode</p> <p>b. Present card, unbrick ok (no-op)</p> </li> <li> <p>a. Press write and unbrick buttons (write-zero mode)</p> <p>b. Present card, overwrite UID with a5a5a5a5 (dummy sequence)</p> </li> <li> <p>Press read button, returning to read mode</p> </li> </ol> <p><code>[int]</code> lines are interrupt-triggered button presses.</p> <h2 id="security-notes">security notes</h2> <p>In general, for <em>secured</em> card systems (those which store and use cryptographic material onboard the cards), a capability which Mifare Classic 1K supports, producing a card with a duplicate UID does not pose a security risk. Cards with cloned UIDs have no capacity to authenticate the user without the key material.</p> <p>That said, Mifare Classic 1K has been cracked -- it is possible to exfiltrate key material and fully clone a card -- but this process takes time, as the card must be attacked repeatedly, and my system does not attempt to do this.</p> <p>If, however, an institution were to be so obtuse as to <em>only</em> use the world-readable and trivially-writable UID as the sole source of authentication information, it would be possible to use this device to functionally replicate user cards freely and, for instance, share card access between potentially-unauthorized principals.</p> <p>I don't know of an institution like that, though.</p> <h2 id="board-design-notes">board design notes</h2> <p>I used 2x8 0.1"-pitch SMD header sockets to accept both the card reader and the MCU, in order to allow me to reuse them between board revisions, if required.</p> 2023-11-08T00:00:00+00:00 2023-11-08T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/input-devices/ <p><a href="https://blog.npry.dev/class/htm/input-devices/cardreader.ino">arduino sketch (breadboard pins)</a></p> <p><a href="https://blog.npry.dev/class/htm/input-devices/cardreader-design.tar.gz">board design</a></p> <p>mcu som: rp2040 xiao</p> <p>Reader Module: <a href="https://amazon.com/dp/B07VLDSYRW">HiLetgo RFID Kit</a></p> <p>Test Cards: <a href="https://amazon.com/dp/B0895Y5LGT">LEXI UID PVC Blanks</a></p> <p>First breadboard version:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cardreader_on.7ec3b3b884ef464b.jpg"> </div> <p>Milled board:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cardreader_board.3b6c1db944f73cc5.jpg"> </div> <p>This week, I made a reader for Mifare cards (of the type used by MIT) with a COTS 13.56MHz card reader. The reader prints the UID of any card presented to it over serial.</p> <p><video src='cardreader_board.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>Note that the LED changes color to a darker blue to indicate that it has succeeded in reading a card.</p> <p>My XIAO board runs a simple Arduino sketch communicating with the reader over SPI, using the MFRC522v2 library.</p> <p>Sample output when one of the test cards is presented:</p> <pre class="z-code"><code><span class="z-text z-plain">read card (sak: 0x08), uid: a5a5a5a5 </span></code></pre> <p>I have plans to add additional I/O to the board, including supporting multiple modes (such as writing cards), so I included buttons on the board that are wired to unused pins.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cardreader_off.926e3f0319f3f3e5.jpg"> </div> <p>There is an IRQ line on marked on the reader module. This is connected as well, and I intend to use it to configure interrupt-driven card reads, though I didn't get to this this week. Notably, it seems to affect the function of the reader if I let it float (detecting card presence when there isn't one), though the documentation suggests it should be an output from the reader IC. I pull it low in the sketch and this appears to make everything work fine.</p> <p>The RGB LED on the board blinks when it reads a card as feedback to the user, and changes to a different shade of blue once it has read a valid card. It flashes red if the read fails (card moving too quickly).</p> <h2 id="milling">milling</h2> <p>I didn't originally mill a board this week -- I came back to this later once I had time to get the board milling process right. This and week was done with a breadboard because development was much faster.</p> <p>Please note: I did <em>design</em> a board for this week to fulfill this requirement -- the design files are available above.</p> 2023-11-01T00:00:00+00:00 2023-11-01T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/machining-something-big/ <p><a href="https://blog.npry.dev/class/htm/machining-something-big/something-big-design-files.tar.gz">design files</a></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chair_complete.3f5e3f04805d9a7c.jpg"> </div> <p><em>cnc router</em>: ShopBot 5' x 10'</p> <p><em>cam</em>: vCarve Pro</p> <p>In pursuit of my final project, I made a chair to calibrate sitting position relative to my rudder pedals. I need several degrees of freedom (primarily chair tilt and back tilt relative to seat base). I went through several design iterations but ended up concerned about structural integrity for all of them, so I just settled on a normal, but short chair that I could block up on the front and the back.</p> <p>The seat back I don't anticipate to require too much iteration, so it's attached with screws and can be adjusted by unscrewing and reattaching.</p> <h2 id="cuts-complete">cuts complete</h2> <p>Here are the parts cut out on the ShopBot:</p> <p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cuts_part1.fbb03b3b32278c38.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cuts_part2.6de4b27371b81f1b.jpg"> </div> </p> <h2 id="chip-out">chip-out</h2> <p>A huge chunk separated from the OSB aggregate during cutting:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chipout.3571e59b28775a94.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chipout_part.d82d3d7197584671.jpg"> </div> <p>I didn't feel it affected structural integrity too much, so I didn't recut the part.</p> <h2 id="autotabs">autotabs</h2> <p>I used autotabs in vCarve Pro, which made it easier to place my parts, but several of the tabs ended up in annoying spots:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;autotabs.6b24a072cf67878d.jpg"> </div> <p>It was relatively easy to cut these out with the corner of the oscillating saw.</p> <h2 id="complete">complete</h2> <p>The fitment ended up quite good -- most of the joints are quite tight. I used an 0.1mm offset on each of the joints.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chair_complete.3f5e3f04805d9a7c.jpg"> </div> 2023-10-25T00:00:00+00:00 2023-10-25T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/machining-casting/ <p>CNC: large-bed ShopBot</p> <p><a href="https://blog.npry.dev/class/htm/machining-casting/machining_casting_design_files.tar.gz">design files (tarball)</a></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;complete_top.7bf96f4b5447c7ab.jpg"> </div> <p>I made a center scribe tool this week. It has a pair of pins with a hole at their midpoint — you line it up on a part or piece of stock you want to find center on and rotate it so the pins touch either side of the piece. Put a pencil or scribe in the center and drag the whole assembly, and you'll mark center on the piece.</p> <p>I did the assignment in two iterations to end up with a metal result that couldn't be produced with &lt;= 3-axis machining. Steps:</p> <ul> <li>CNCed wax positive</li> <li>Cast two-part silicone mold</li> <li>Cast plaster part</li> <li>Cleaned up / finished plaster part and drilled through-hole</li> <li>Cast one-piece silicone cut mold around plaster part</li> <li>Cast metal part in one-piece cut mold</li> </ul> <h2 id="milling">milling</h2> <p>The CAM software we trained on was ShopBot vCarve, using functionality to cut a part in a half and CNC out each half. Initially, I tried to follow this approach, using a baseplate with locating pins in it for each mold-half.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;partial_model.50b1c188c9d339e9.jpg"> </div> <p>Unfortunately, vCarve saw the whole item as the model and tried to route around the border of the baseplate to separate it from the rest of the stock. I didn't want this — I just wanted the faceplate to sit in a pocket.</p> <p>John and I worked on this and found that using my original assembly (from which the plate models were derived) would work if we adjusted the vCarve settings.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;model.e7fdef1c8622e7df.jpg"> </div> <p>I used the large format ShopBot in the CBA shop to mill the design:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;milling.a26332fbeb7a80b9.jpg"> </div> <p>Partway through roughing, communications failed with the ShopBot:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;shopbot_error.e8506b9da2b70544.jpg"> </div> <p>John and I wrote down the gcode line we were on and hoped we would be able to resume the job, but the machine had lost its XY zero after restart. You can see on the final result that it drove the endmill straight through the far wall after we restarted:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;complete.0efff242059cb784.jpg"> </div> <p>We rezeroed it in XY after that, and though that zero wasn't perfect, the roughing pass had left enough excess stock in most areas that the finishing cut was able to recover the part well. The large pins had small bites taken out of them in one layer, but this was okay for my purposes.</p> <p>You can see that the ShopBot wasn't able to cut the through-hole in the bottom part above — I add that later manually.</p> <h2 id="silicone">silicone</h2> <p>I cast a silicone mold from the wax positive:</p> <p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;bottom.0d55f279e4286547.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;top.a2d622e12301ad81.jpg"> </div> </p> <p>In order to fill the mold, I made two of the handles into pour holes/sprues:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cut_through.498f9738bd3031da.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pour_spouts.d9e09ba1d2ebc5b5.jpg"> </div> <p>To keep it together, I made a cardboard and tape holder with slight preload:</p> <p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mold_holder_top.8763e3cc29f8893a.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mold_holder_high_side.07e8c21d3e474e19.jpg"> </div> </p> <h2 id="plaster">plaster</h2> <h3 id="attempt-1">attempt 1</h3> <p>Here is the mold filled with plaster:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;poured.34f561851e3f5502.jpg"> </div> <p>I weighted it down to try to minimize flash:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weighted.c60f74130ff278fd.jpg"> </div> <p>The first pour had a huge bubble in it:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;bubble.e7f031c7398be769.jpg"> </div> <p>And one of the bottom posts didn't fill due to an air bubble:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;post_bubble.3a15829f839b866b.jpg"> </div> <h3 id="attempt-2">attempt 2</h3> <p>I repoured, this time directly filling the bottom posts before closing the mold. I also left the mold on the vibratory plate for much longer and rotated it a lot to try to ensure I got all the air out. I caught a small bubble on the top:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clean_top_init.92e45bd80dc74942.jpg"> </div> <p>And another few small ones on the bottom posts:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;clean_bottom_init.43a3b48d1fb4c474.jpg"> </div> <p>But these were small enough not to bother me.</p> <h3 id="touchups">touchups</h3> <p>I tried touching up both pours by filling the voids with additional plaster:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;retouched.29eb88129090d6be.jpg"> </div> <p>Clearly the first mold couldn't be made functional (as the post was almost entirely missing), but I wanted to see how well the large void on top would fill and whether it would crack. I haven't cleaned this up yet, but it seems not to have cracked, somewhat to my surprise.</p> <p>Here's the nicer one after the touchups cured and I went over the whole piece with some fine sandpaper:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;touched_up.4c0f8ab614844d06.jpg"> </div> <p>I then added the through-hole for the scribe with a dremel:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;hole_drilled.648d902b4d9b671c.jpg"> </div> <h2 id="one-piece-cut-mold">one-piece cut mold</h2> <p>I put the nicer plaster model on a cardboard base, then poured silicone around it to produce a mold that captures the scribe-hole and all my retouching:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cut_mold_pour.89c4a065d313c111.jpg"> </div> <p>I used hot glue to attach the piece to the base, and I whittled a couple of the actual hot glue sticks to make vents.</p> <p>Cut it open to extract the positive:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cut_mold_open.8c2b38dafc139cf8.jpg"> </div> <p>The plaster survived but has little bits of silicone stuck in it everywhere:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;post_remold.06f30d0c277aa900.jpg"> </div> <p>Here's the mold closed by hand with most of the parting lines vanishing:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cut_mold.aeab78c0e9748f7b.jpg"> </div> <p>Top-down view of the result (filled vent is obscuring the hole).</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;casting_fresh_top.7ff52e4484b7db82.jpg"> </div> <p>Side view:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;casting_fresh_side.a87b224115d143bd.jpg"> </div> <p>I cut off the bulk of the excess material with a hacksaw:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;cutoffs.852724e043192a3d.jpg"> </div> <p>And refinished the rest with a file in a pair of soft jaws:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;filing.a2f7af9ff17688f4.jpg"> </div> <p>Here's the completed part:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;complete_top.7bf96f4b5447c7ab.jpg"> </div> <p>Unfortunately, the low-temperature alloy I cast with was softer than I expected, and I squeezed one of the pins in the vice to file the top. It deformed pretty badly:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;complete_bottom.f7bfa145fb49fb86.jpg"> </div> 2023-10-18T00:00:00+00:00 2023-10-18T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/elec-production/ <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;board_complete.3d7d8f15be49f211.jpg"> </div> <p><a href="https://blog.npry.dev/class/htm/elec-production/elec_production_design_files.tar.gz">design files (tarball)</a></p> <p>Recall that as part of my final project, I am making an I/O board with button-bearing daughterboards that will handle the buttons on an MFD:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd.c40d6618c31a11af.jpg"> </div> <p>Daughterboard and I/O master board designed last week:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;button_daughterboard.1204d6f7e57f0d3a.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;io_master.6256c938099e18b8.jpg"> </div> <p>I milled the I/O master board this week in Reponsive Environments' PCB router:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pcb_router.ed5960ac7f9c0c86.jpg"> </div> <h2 id="partial-redesign">partial redesign</h2> <p>I redesigned the boards this week because I realized last week's was needlessly complicated — I wasn't making use of the fact that the GPIOs have pullups, which meant I routed power to each daughterboard and needed to add resistors for current-limiting.</p> <p>I removed that requirement, cutting out two wires per daughterboard connection (I had rounded up to 8 wires using two grounds, since I didn't want an odd number of pins in my connector). More importantly, the lack of power going to all connectors drastically simplified the single-layer routing topology problem and allowed me to use larger traces (much nicer for PCB milling).</p> <p>I also added SMD debounce capacitors (22μF — just what I could find around ResEnv in quantity 25) to the I/O master, as I've never implemented debouncing in hardware before and wanted to try this. Unfortunately, these additional footprints along with my desire to keep the design compact caused me to <em>decrease</em> my trace width and spacing significantly. This would come back to bite me later.</p> <h3 id="debounce-verification">debounce verification</h3> <p>I built a prototype of the debounce circuit before I milled anything to verify behavior:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;button_debounce.62f5bcd9dd2c3f42.jpg"> </div> <p>Here's a plot of a button actuation at the measurement point on my scope, full vertical range 0V - 3.3V, 10ms/div:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;debounce_scope.401e24f120bc6738.jpg"> </div> <p>I tried a bunch and couldn't produce a button press that was noticeably noisy.</p> <p>Then I built the same circuit using the SMD caps I had on some protoboard — back:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;protoboard_debounce_back.9035907ab458c01e.jpg"> </div> <p>And front, with button:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;protoboard_debounce_front.6485cda97b2df734.jpg"> </div> <p>I saw similar performance with this protoboard version of the circuit, validating the design.</p> <h3 id="aside-tantalum-caps">aside: tantalum caps</h3> <p>I believe the capacitors I found are tantalums. It's hard to know for sure, as they were in an unmarked reel-tape, but they do have a polarity marking. Tantalums have the opposite polarity-marking convention as electrolytics, so this makes deciding which way to orient them a dilemma.</p> <p><em>Prima facie</em>, that they are in an SMT package suggests that the caps <em>are</em> tantalums, as to my knowledge elecrolytic caps are not packaged for SMT this way. However, I could be wrong, so I wanted to do some investiagion.</p> <p>I used a multimeter to check the capacitance in both directions, hoping something about their polarization would cause the reading to be obviously different one way. This wasn't the case — I got 22μF both ways.</p> <p>I installed them in my test circuit under the assumption they were tantalums, and nothing blew up, so that lends some credence. They're marked 5V as well, and my circuit is at 3.3V, so it's not like they're way under their rating.</p> <p>On the other hand the resistor in this test circuit limits current to 2mA maximum (at 3.3V), so let's generously say the capacitor could convert 10mW to heat under the worst conditions. This seems unlikely to generate enough temperature differential to cause a catastrophic failure, supposing the caps are of a different type.</p> <p>So, altogether hard to say, though it seems circumstantially likely that they are tantalums.</p> <h2 id="milling">milling</h2> <p>I used FlatCAM as my CAM tool this week and Candle as my machine controller (communicating to the router over USB serial).</p> <p>I had a lot of trouble getting my boards to mill properly. Initially, I wasn't getting enough depth of cut — the first run didn't make it through the copper. A later run was well-enough calibrated (but still wrong) that it only <em>burnished</em> the top surface of the copper without cutting.</p> <p>I had difficulty debugging these problems because FlatCAM and Candle are both new to me, so attribution of the behavior was difficult. I'd think I had solved one problem, but it would surface another one, and I couldn't tell e.g. if I wasn't cutting deep enough because I was zeroing the machine incorrectly (or upsetting the zero, etc.) or because FlatCAM wasn't setting a deep enough cut depth in the first place.</p> <p>Eventually I understood what each tool wanted and got everything working, including Candle's heightmap feature:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;candle_heightmap.b3779aeffad09357.jpg"> </div> <p>Red areas are high, blue are low — for our PCB mill, the bed slopes down to the right, so the zero is correct on the left, but drastically off on the right.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;candle_heightmap_table.b6f193b7cc0f0b64.jpg"> </div> <p>This is the table of each probe point (in mm). Our depth of cut is only 0.15mm, so we would expect to stop cutting entirely halfway across the bed. In practice, this doesn't actually happen, which (along with a tendency to mill overly-wide paths with our v-bits) leads me to believe our zero process has some bias. In any case, there is a lot of drop-off wrt. our depth-of-cut across the bed, so this mesh bed-leveling process should be helpful.</p> <p>Once I got to this point, I quickly realized my design wasn't going to work. The trace width and trace spacing reduction (both 0.25mm) I had made to accommodate the debounce caps made the traces too narrow for our mill — they were either very stringy (tending to get grabbed by the mill and ripped off) or missing entirely.</p> <h2 id="reredesign">reredesign</h2> <p>I redesigned again, this time omitting the debounce caps entirely and just resolving to handle this in firmware. The I/O master board is very simple now:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;new_io_master.439e040332892deb.jpg"> </div> <p>It just forwards ground and 5 button IOs to a pin header connector. This is at the very least nicer for my application than directly plugging the button IOs into the Pico as we can share ground in groups of 5 IOs rather than 4.</p> <p>NB: there is 1 extra button group of 5 IOs for auxiliary functions on the MFD (day/night, brightness encoder, contrast).</p> <p>I increased the trace width to a full 1mm and minimum clearance to 0.5mm to ensure we would mill cleanly.</p> <h2 id="milling-part-2">milling, part 2</h2> <h3 id="shifting">shifting</h3> <p>The last hurdle to clear was the board shifting during milling. I had seen this several times, and am still not sure why, beyond potentially inconsistent application of double-stick tape. I even tried my first attempt with halved feedrate in an attempt to minimize tool force on the part, but it still shifted:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;shifting.bed8b90e975edab1.jpg"> </div> <p>(This is on the back of my successful board — ignore the pins.)</p> <p>The pads are all meant to be the same size as the six on the right, but you can see that the last four get successively smaller as the double-stick tape started to release and the board really started to move, at which point I killed the job.</p> <h3 id="success">success</h3> <p>The next attempt worked. I didn't change anything beyond making sure I held firm pressure on the board for 30-45 seconds to ensure it had the best bond with the tape possible.</p> <h2 id="drilling">drilling</h2> <p>Operationally, drilling proceeded smoothly. I could keep the same zero and heightmap and just start it. I was conservative and started at 33% feedrate, and slowly ramped to ensure nothing would break. It completed without shifting or any other issues from the machine.</p> <h3 id="drill-depth">drill depth</h3> <p>However, functionally, I did hit problems. First, I hadn't set the drilling depth deep enough (1.7mm, should have used 2mm), so the drill failed to pierce the copper on the back side of my FR1. I hadn't noticed this until I had pulled the part off of the mill, or I would have just re-drilled it. Instead, I finished the drilling manually with the same bit in a Dremel — the existing holes made this easy.</p> <p>The downside to doing this was that I didn't have a backer board, so I had little copper tags attached to most of the holes. This was an issue because they would almost certainly contact the header pins and short all of them to each other. I removed them by hand using a drill bit as a deburring and slight countersink tool.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chamfer_bit.092e746269a72093.jpg"> </div> <p>This had the added benefit of relieving the copper at the edges of the holes, making incidental contact between pins and the bottom plane of the board almost impossible.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chamfered_holes.4650341a9d14455e.jpg"> </div> <h3 id="oversize-holes">oversize holes</h3> <p>The second problem was larger: the holes were oversize. Nominally, they should have been 1mm, but the endmill I had measured 1.06mm. I didn't think this would be too much of an issue, as the thinnest annular width I had for any pads was 0.35mm — the oversized endmill should have only affected this by 0.03mm per side, i.e. &lt; 10%.</p> <p>Unfortunately, I actually totally lost most of my small pads. If you recall, I wasn't able to mill traces at 0.25mm, so 0.03mm was 33% of the way from our 0.35mm to a known non-working configuration — suddenly much more significant. That's not to say that a 1mm endmill would necessarily have done the trick, but it's likely we're playing with the border of process stability, so that small change was much more significant than I expected.</p> <h2 id="soldering">soldering</h2> <p><em>better known as: i sure wish i had some solder mask</em></p> <p>The result of this drilling mishap is that I spent several hours soldering and continuity-testing the board. Perhaps a better term than soldering would be "solder sculpting" — to get the solder to bridge only to the header pin I wanted across a void where a pad should be and without solder mask (mostly: without bridging to my ground pour), I had to develop some techniques.</p> <p>It is first worth noting that I had all my trouble connecting the header pins, which are the connectors for the daughterboards, and are through-hole. The castellated edge on the Pico was very straightforward and took me all of two minutes.</p> <h3 id="techniques">techniques</h3> <ul> <li> <p>General principles:</p> <ul> <li>Solder "likes" heat — it tends to move towards the hot thing</li> <li>Effective heat conduction increases nearly as a stepfunction when solder melts — as a liquid, solder drastically increases its surface area with the iron <em>and other solder</em>, meaning the iron is more heat-efficient and more solder is exposed. This is a cascading effect.</li> <li>Electrical nets are correlated to thermal nets</li> <li>A hot board / still-hot solder melts much more rapidly</li> <li>In general, for "atypical" soldering techniques I'm discussing here: if you don't get the result you want, don't keep trying — remove the iron immediately, wait for the board to cool, and try again. It only gets more difficult to be precise the hotter the board is.</li> </ul> </li> <li> <p>"Flicking" solder: build up an oversized blob of solder on a trace, then lift it with the point of the soldering iron. The bottom of the blob stays stuck to the trace, and gravity keeps most of the mass there. You end up with a tail of solder that you can lay on top of the pin you want to solder to and remove the iron so as to elongate the tail. The joint with the pin (if any) will be cold, so you will need to touch it up. It can help to build a blob, wait and let it cool (not just to where it solidifies, but for 10 or 20 seconds so it loses residual heat), and only then flick it — hotter solder is runnier, and we want it to be viscous here.</p> </li> <li> <p>"Tapping": in most cases, the cascading increase in heat conduction due to solder melting is helpful. However, if we want to touch up a joint, this effect can lead to everything becoming one big contiguous puddle of solder very quickly. With a well-timed application of the iron you can sometimes manage to affect only part of a joint, or to quickly bridge two parts together without wrecking the rest of the solder structure. Suppose we've "flicked" a tail near a pin (but not touching). We can connect the tail and the pin by flicking a tail from the pin and tapping to weld them together. This works best if there is a natural heat brake — a piece of (non-solder) metal in the conduction pathway can stall other parts of the solder body from melting and give you some time to work locally.</p> </li> <li> <p>Preheating: for both flicking and tapping, if you can selectively preheat the part you won't be acting on, it makes it much easier to produce a solid joint — it will tend to attract solder.</p> </li> <li> <p>"Towering": it's possible to build a solder tower by tapping successive blobs on top of each other. This is useful if you can establish a known-non-shorted base blob on a trace and then tower up (usually once) to flick to a pin, because it means you need much less of a large blob.</p> </li> <li> <p>"Pin blobbing": I discovered over time that this was the most consistent approach for most pins. Rather than trying to flick from a trace, build up a blob on a pin, ideally let it cool <em>somewhat</em>, and flick to the trace. Traces are usually packed more closely to other traces and the ground plane than pins, which have breathing room for the pad, so building a blob on the pin is preferable. Flicking quickly and at the right timing after placing the blob makes this work — a blob with some heat will tend to pull solder towards it, and if you make the flick fast (i.e. cold), you will minimize risk of bridging to an unintended net. Again, a preheated target trace will tend to improve the chances of a nice joint without needing to touch up.</p> </li> </ul> <h3 id="ground-connections">ground connections</h3> <p>The ground connections were the absolute worst to solder. They have thermal relief intentionally and a copper pathway for solder to spill to the ground plane, so it's impossible to keep a solder blob within the pad. I needed to tower for these, for the most part. They also need to be done first, because the quantity of solder you need to make these connections means that they will frequently bridge to other already-complete pin connections and melt them into a big blob.</p> <h3 id="connectivity">connectivity</h3> <p>I verified my joints with a multimeter and microscope. To my knowledge, everything is electrically connected properly, except one GPIO that is shorted to ground. I believe that issue must be underneath the Pico, as I've scoured all along the visible parts of it and can't find anything wrong.</p> <p>I specifically checked every connection against bridging to ground and the board's nominally floating reverse plane. I didn't do a pairwise pin-pin check for shorts, and I haven't checked against power, either. Each assigned GPIO on the Pico <em>does</em> have continuity to its corresponding pin on the headers.</p> <p>There is only one GPIO that is shorted to the reverse side's copper plane, so other than being a big antenna, it should work properly. The reverse plane is not shorted to ground.</p> <p>Unfortunately, there are 6 test points on the reverse of the Pico that I didn't account for in my design — I anticipate they are shorted together and to ground. I haven't checked the schematic for what they connect to, but I would expect that it breaks the board.</p> <h2 id="programming">programming</h2> <p><strong>NB: To the extent this matters for the grade, I did successfully program a nearly-equivalent board for my <a href="../final-tracking/">final project</a> with almost exactly this firmware.</strong></p> <p>Unsurprisingly, given that I think the board wouldn't power on, I didn't program the board for this week. It's very basic firmware for what I need — could just be a polling loop:</p> <pre data-lang="c++" class="language-c++ z-code"><code class="language-c++" data-lang="c++"><span class="z-source z-c++"><span class="z-comment z-line z-double-slash z-c"><span class="z-punctuation z-definition z-comment z-c">//</span> This firmware prototype intended for use with Arduino framework. </span></span><span class="z-source z-c++"> </span><span class="z-source z-c++"><span class="z-meta z-preprocessor z-include z-c++"><span class="z-keyword z-control z-import z-include z-c++">#include</span> <span class="z-string z-quoted z-other z-lt-gt z-include z-c++"><span class="z-punctuation z-definition z-string z-begin z-c++">&lt;</span>Joystick.h<span class="z-punctuation z-definition z-string z-end z-c++">&gt;</span></span> </span></span><span class="z-source z-c++"> </span><span class="z-source z-c++">Joystick_ <span class="z-meta z-function z-c++"><span class="z-meta z-toc-list z-full-identifier z-c++"><span class="z-entity z-name z-function z-c++">joystick</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-punctuation z-terminator z-c++">;</span> </span><span class="z-source z-c++"> </span><span class="z-source z-c++"><span class="z-storage z-modifier z-c++">constexpr</span> <span class="z-support z-type z-stdint z-c">uint8_t</span> N_BUTTON <span class="z-keyword z-operator z-assignment z-c">=</span> <span class="z-constant z-numeric z-integer z-decimal z-c++">25</span><span class="z-punctuation z-terminator z-c++">;</span> </span><span class="z-source z-c++"> </span><span class="z-source z-c++"><span class="z-storage z-modifier z-c++">const</span> <span class="z-storage z-modifier z-c++">static</span> <span class="z-support z-type z-stdint z-c">uint8_t</span> PIN_MAP<span class="z-meta z-brackets z-c++"><span class="z-punctuation z-section z-brackets z-begin z-c++">[</span>N_BUTTON<span class="z-punctuation z-section z-brackets z-end z-c++">]</span></span> <span class="z-keyword z-operator z-assignment z-c">=</span> <span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-begin z-c++">{</span> </span></span><span class="z-source z-c++"><span class="z-meta z-block z-c++"> <span class="z-comment z-line z-double-slash z-c"><span class="z-punctuation z-definition z-comment z-c">//</span> elided </span></span></span><span class="z-source z-c++"><span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-end z-c++">}</span></span><span class="z-punctuation z-terminator z-c++">;</span> </span><span class="z-source z-c++"> </span><span class="z-source z-c++"><span class="z-storage z-type z-c">void</span> <span class="z-meta z-function z-c++"><span class="z-meta z-toc-list z-full-identifier z-c++"><span class="z-entity z-name z-function z-c++">setup</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-meta z-function z-c++"> </span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-begin z-c++">{</span></span></span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> <span class="z-keyword z-control z-c++">for</span> <span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span><span class="z-storage z-type z-c">auto</span> pin <span class="z-keyword z-operator z-ternary z-c">:</span> PIN_MAP<span class="z-punctuation z-section z-group z-end z-c++">)</span></span> <span class="z-meta z-function-call z-c++"><span class="z-variable z-function z-c++">pinMode</span><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-function-call z-c++"><span class="z-meta z-group z-c++">pin<span class="z-punctuation z-separator z-c++">,</span> INPUT_PULLUP</span></span><span class="z-meta z-function-call z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-punctuation z-terminator z-c++">;</span> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> joystick<span class="z-punctuation z-accessor z-dot z-c++">.</span><span class="z-meta z-method-call z-c++"><span class="z-variable z-function z-member z-c++">begin</span><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-method-call z-c++"></span><span class="z-meta z-method-call z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-punctuation z-terminator z-c++">;</span> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"></span></span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-end z-c++">}</span></span></span> </span><span class="z-source z-c++"> </span><span class="z-source z-c++"><span class="z-storage z-type z-c">void</span> <span class="z-meta z-function z-c++"><span class="z-meta z-toc-list z-full-identifier z-c++"><span class="z-entity z-name z-function z-c++">loop</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-function z-parameters z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-meta z-function z-c++"> </span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-begin z-c++">{</span></span></span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"> <span class="z-keyword z-control z-c++">for</span> <span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span><span class="z-storage z-type z-c">auto</span> i <span class="z-keyword z-operator z-assignment z-c">=</span> <span class="z-constant z-numeric z-integer z-decimal z-c++">0</span><span class="z-punctuation z-terminator z-c++">;</span> i <span class="z-keyword z-operator z-comparison z-c">&lt;</span> N_BUTTON<span class="z-punctuation z-terminator z-c++">;</span> i<span class="z-keyword z-operator z-arithmetic z-c">++</span><span class="z-punctuation z-section z-group z-end z-c++">)</span></span> <span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-begin z-c++">{</span> </span></span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-meta z-block z-c++"> <span class="z-storage z-type z-c">auto</span> pin <span class="z-keyword z-operator z-assignment z-c">=</span> PIN_MAP<span class="z-meta z-brackets z-c++"><span class="z-punctuation z-section z-brackets z-begin z-c++">[</span>i<span class="z-punctuation z-section z-brackets z-end z-c++">]</span></span><span class="z-punctuation z-terminator z-c++">;</span> </span></span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-meta z-block z-c++"> <span class="z-storage z-type z-c">auto</span> state <span class="z-keyword z-operator z-assignment z-c">=</span> <span class="z-meta z-function-call z-c++"><span class="z-variable z-function z-c++">digitalRead</span><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-function-call z-c++"><span class="z-meta z-group z-c++">pin</span></span><span class="z-meta z-function-call z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-punctuation z-terminator z-c++">;</span> </span></span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-meta z-block z-c++"> </span></span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-meta z-block z-c++"> joystick<span class="z-punctuation z-accessor z-dot z-c++">.</span><span class="z-meta z-method-call z-c++"><span class="z-variable z-function z-member z-c++">setButton</span><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-begin z-c++">(</span></span></span><span class="z-meta z-method-call z-c++"><span class="z-meta z-group z-c++">i<span class="z-punctuation z-separator z-c++">,</span> state</span></span><span class="z-meta z-method-call z-c++"><span class="z-meta z-group z-c++"><span class="z-punctuation z-section z-group z-end z-c++">)</span></span></span><span class="z-punctuation z-terminator z-c++">;</span> </span></span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-meta z-block z-c++"> <span class="z-punctuation z-section z-block z-end z-c++">}</span></span> </span></span></span><span class="z-source z-c++"><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"></span></span><span class="z-meta z-function z-c++"><span class="z-meta z-block z-c++"><span class="z-punctuation z-section z-block z-end z-c++">}</span></span></span> </span></code></pre> <p>Ideally I'd make it work with interrupts, but this would be fine.</p> <p>As I said, I would have tested this, but I'm pretty sure the board I have would die if I plugged it into power, and I'm out of time for this week to debug it or produce another.</p> <h2 id="improvements">improvements</h2> <p>The easiest and most significant improvement I think would have been not using through hole parts. I thought this would be interesting, but it really didn't work. Surface-mount connectors and I could have been done with the soldering in less than 15 minutes, and I wouldn't have needed to drill at all (not that this took that long).</p> <p>The better project this week would have been the daughterboards, as these are simple and lend themselves much more readily to exploring milling a board, but they're larger than the capacity of resenv's PCB mill, so I would have needed to use the CBA one. Unfortunately, there were multiple people lined up to use it every time I stopped by, so I couldn't do it this week.</p> 2023-10-11T00:00:00+00:00 2023-10-11T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/elec-design/ <p><a href="https://blog.npry.dev/class/htm/elec-design/elec_design_files.tar.gz">design files</a></p> <p>I used KiCad to design a pair of boards for my <a href="../final-tracking">final project</a>. These will be button I/O boards for the MFDs:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd.6bd146b127bd488f.jpg"> </div> <h2 id="daughterboards">daughterboards</h2> <p>First I designed 4 daughterboards, each of which handles one side of the MFD (5 buttons).</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;button_daughterboard.f4920673bfb58d58.jpg"> </div> <p>Each button is low-passed with a 1uF capacitor and a 10k resistor for debounce. In theory, this should lead to rolloff starting at around 15Hz.</p> <p>These boards will mount on the backside of the MFD bezel with screws. The hole pattern is TBD based on the final MFD design.</p> <h2 id="i-o-master">i/o master</h2> <p>I designed the master board based on a Raspberry Pi Pico as a SoM:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;io_master.c52970f35087ab3f.jpg"> </div> <p>It interfaces with the daughterboards using 8-pin JST connectors, providing 3.3v, 2x ground, and 5x button outputs.</p> <p>The Pico is soldered to the board using the castellated edge, though I'm considering redoing the layout with a pair of header sockets to make it swappable.</p> <p>I chose the Raspberry Pi Pico for its high available GPIO count (26 available pins), meaning each MFD can be serviced by one Pico.</p> <p>I intend to have this board communicate with the host computer using the USB port on the Pico.</p> 2023-10-04T00:00:00+00:00 2023-10-04T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/3dprint/ <p>I designed and printed a captive pair of diagonal racks as a fidget toy.</p> <p><a href="https://blog.npry.dev/class/htm/3dprint/rack_design_files.tgz">design files (tarball)</a></p> <p>I used my own 3d printers for this week. I both wanted to try an SLA print here (CBA shop training hasn't covered this yet), and be able to take my time/not worry about blocking other people's prints.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;finished_sla.797ba0db5a94395c.jpg"> </div> <p>The cage and each rack are separate parts, but the design has them printed in place. The cage slides along both racks simultaneously, and each rack engages with and slides along the teeth of the other.</p> <p><video src='rack_anim.webm' type="video/webm" loop muted autoplay style="width: 600px"></video></p> <p>The design couldn't be manufactured subtractively because the racks are captive in the cage, and the cage is one piece. (Probably you could do this with very careful application of wire EDM, but this design at least couldn't be <em>machined</em>).</p> <p>Obviously, the difficult part of this is getting the print-in-place to work without bridging the parts together. So far, I haven't succeeded.</p> <h3 id="attempt-1-sla">attempt 1: sla</h3> <p>The first attempt was on my Anycubic Photon S with a generic SLA resin I bought on Amazon.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;anycubic_table.d1641b85c4d9dea2.jpg"> </div> <p>I printed the model at a 45 degree angle with the rack teeth oriented vertically. I was hoping this would eliminate any directional bias / sag due to weight and keep the teeth separate.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_slicer.873f13e185bdb184.jpg"> </div> <p>I designed the model with an 0.5mm gap between all the moving elements in order to reduce the chances of unintended bridges between parts. I verified that this gap was correctly sliced into the model:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_layer_with_separation.60241bbf5d5e7257.jpg"> </div> <p>The above image is the core of the mechanism: the cage (outer green ring) containing both racks, which are engaged with each other in this layer. The notable thing is that all the parts are separated by several black pixels, meaning that there should be free space between them.</p> <p>In principle, I'm relying on the rigidity of the printed structure to maintain the gaps in the model, at least sufficiently that the parts aren't bridged together. Unfortunately, pre- or partially-cured resin is somewhat flexible, and a structure that is intended to be three separate parts has almost no rigidity.</p> <p>Bow in one of the racks:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_bow.89517be489ad448c.jpg"> </div> <p>The model can also be shifted by the contact with the tank membrane as it is lowered back against the screen.</p> <p>The printed structure bridged in many places. On this side, the cage bridged directly to the bottom plane of the rack:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_welded_cage_top.bc03ba44f32e9f1d.jpg"> </div> <p>Note the top seam is too tight / there is no gap, where there should be 0.5mm.</p> <p>In this image, we're showing a healthy gap between the side of the cage and the rack, suggesting that the parts may have been free and independent initially, before they eventually bridged:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_gap.c9df08d22bbf0287.jpg"> </div> <p>Rack teeth bridged together:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;sla_welded_teeth.b6a3880d364c322d.jpg"> </div> <p>I was not surprised that there was bridging, but I was hopeful that it would be intermittent enough that I could break the bridges and get the mechanism to move. I tried flexing the part and pushing each rack both along its axis and along the axis of its teeth, but I wasn't able to break it loose. I'm fairly confident, however, that both racks are fully or mostly bridged along their back plane onto the cage, meaning it'd be unlikely I could ever get this apart without very involved surgery.</p> <p>If I were to do this again, I would pre-bridge all of the parts together in a way that fixed and rigidified their intended relationships in the interfacing region. I would design this bridging to be easy to remove and clean up after the fact.</p> <h3 id="attempt-2-fdm">attempt 2: fdm</h3> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;ender3_midprint.d9d57b862594ca92.jpg"> </div> <p>I didn't have time to redesign and reprint the part before class, but I figured I could try the same print in FDM, so I printed the same design (0.5mm separation) on my Ender 3 in PLA+.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fdm_sliced.74bf002d534d3fd5.jpg"> </div> <p>I chose to print with the cage flat against the bed. This required significant manual support painting, as I exported the assembly (both racks + cage) as a single STL object in order to maintain alignment -- PrusaSlicer had no way of knowing that I didn't want parts to rest or sag onto each other.</p> <p>On reflection, I should probably have printed this standing up, as I think this would have minimized surface area for tolerance-critical supports, though that trades off against a less stable / higher aspect-ratio print.</p> <p>Painted supports on either side of the bottom rack, bridging over the bottom of the cage (cutaway):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fdm_slice_bridge.bc60c926bb9b80f1.jpg"> </div> <p>I chose to paint support material under the teeth within the cage, which couldn't be supported from the bed. I reasoned that having some low-density material here that could be broken away would be better than potential hard bridges:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fdm_slice_cutaway_supports.8663db334d6187e1.jpg"> </div> <p>Airgap between teeth:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fdm_slice_airgap.de52ac4a6c212c9e.jpg"> </div> <p>Unfortunately, the bridges here sagged too much and I didn't have my supports dialed in well enough -- I couldn't get it apart.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fdm_complete.9ccd465043b3832d.jpg"> </div> <h2 id="scan">scan</h2> <p>I scanned an eraser and an RS232 programmer with the Leo:</p> <script type="module" src="https://ajax.googleapis.com/ajax/libs/model-viewer/3.1.1/model-viewer.min.js"></script> <p><model-viewer src="remeshed.glb" shadow-intensity="1" camera-controls touch-action="pan-y" style="width: 640px; height: 480px;"></model-viewer></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;eraser.86f456076c26b727.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;programmer.2e7419dc69340d45.jpg"> </div> 2023-10-02T00:00:00+00:00 2025-10-14T00:00:00+00:00 Nathan Perry https://blog.npry.dev/tourmaline/ <p>I started this project in response to my experience with <a href="/class/htm/embedded">my how-to-make embedded project</a>, which was an exercise in being disappointed by <a href="https://www.atomvm.net/">atomvm</a>.</p> <p><code>tourmaline</code> is an attempt to port <a href="https://erlang.org">Erlang</a> to <code>#![no_std]</code> Rust, split into several crates, presently: a BEAM file serializer/deserializer, an ETF serializer/deserializer, BIF implementations, interface traits, native term types, and a runtime.</p> <p>I did a good chunk of work by the time I got pulled off into other things — I was hoping to be able to evaluate some simple bytecode soon. I plan to get back to this, but frankly the amount of mental RAM I need to page in from very stale cache is daunting, so it may take a long time.</p> <h2 id="concept">concept</h2> <p>The short version is that I think it'd be neat and useful to be able to embed Erlang into more contexts — as kind of a very-high-functioning scripting language that could run in other software and on embedded devices. Joe Armstrong got most of the primitives right.</p> 2023-09-27T00:00:00+00:00 2023-09-27T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/embedded/ <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;blinky.29c7197f9e4df6c1.jpg"> </div> <p><strong>dev board</strong>: esp32-c3 xiao</p> <p><em>note: reviewing this week, I realized I didn't demonstrate a video of the board working in this documentation. Please see <a href="../networking-comms/">networking</a> for a video of a later version of this board design working.</em></p> <p>I took this week in the direction of doing two implementations in two different languages.</p> <p>Source code listings are included as a tarball <a href="https://blog.npry.dev/class/htm/embedded/src.tgz">here</a>.</p> <h2 id="rust">rust</h2> <p>I wrote a <a href="https://rust-lang.org">rust</a> implementation first using Espressif's <a href="https://github.com/esp-rs">esp-rs</a> tooling.</p> <p>My first approach here was the <code>esp_idf_hal</code> crate<sup class="footnote-reference"><a href="#1">1</a></sup>, which is implemented on top of Espressif's C SDK (ESP-IDF). This was easy to get up and running -- I was able to blink an LED and poll <a href="https://httpbin.org">httpbin</a> to verify WiFi connectivity, while outputting to a terminal via the virtual USB serial port.</p> <p>This took some doing, but the overhead was much lower than for the original ESP32 or the S series, as the upstream Rust compiler has support for RISC-V, but not for Xtensa. You still do need to install <code>esp-idf</code> itself in order to build, which is annoying, because it's a huge tentacle monster of git submodules and custom build tooling. Rust build scripts in the <code>esp_idf_hal</code> crate mostly handle this, but I run <a href="https://nixos.org">NixOS</a>, so my system is as a rule not amenable to random build processes being able to mutate the system, install their own dependencies, and also assume that bash lives in <code>/bin/</code>. I was able to hack it in eventually by excising several heuristic checks in the esp-idf build scripts that didn't believe that they weren't already in a virtualenv.</p> <p>In other news, I discovered some nice tooling here -- <code>cargo-espflash</code> gives a single-command compile-upload-and-monitor without also forcing you to live with a whole monolithic blob of dead weight like PlatformIO. So nice to have tooling developed by people who believe in clear, decoupled interfaces; Unix philosophy, etc. etc.</p> <h3 id="part-1-5-pure-rust">part 1.5: pure rust</h3> <p><code>esp_idf_hal</code> was not particularly satisfying -- it is, for one thing, mostly C. While much of the world is built on C, I prefer Rust if I can get it, and there is a pure-Rust implementation of most everything <code>esp_idf_hal</code> gives you in <code>esp32**_hal</code> (in our case <code>esp32c3_hal</code>, though there is a crate for each Espressif MCU model). Furthermore, Rust has a burgeoning community of embedded libraries and projects that actually attempt to interoperate with each other.</p> <p><code>esp_idf_hal</code> does make an attempt to participate, but I didn't find it that effective -- ideally, it would handle chip-specifics and then get out of your way to make using the generic interfaces as usable as possible, but Espressif seems more interested in implementing a whole HTTP stack from scratch on their own instead, and then having you use that. Not really my cup of tea -- I am desperately hoping for a world where I can use the same HTTP client on a Linux environment as on an MCU.</p> <p>Main, relevant open-source Rust projects:</p> <ul> <li> <p><code>embedded-rust</code> is a github org with a set of interface crates that abstract different parts of the computational stack</p> <ul> <li><code>embedded-hal{,-async}</code> (abstracting hw peripherals)</li> <li><code>embedded-io{,-async}</code></li> <li><code>embedded-nal{,-async}</code> (<strong>N</strong>etwork <strong>A</strong>bstraction <strong>L</strong>ayer)</li> <li><code>embedded-time</code></li> </ul> </li> <li> <p><code>embassy</code>: embedded async runtime, notably including</p> <ul> <li><code>embassy-executor</code> (async executor itself)</li> <li><code>embassy-sync</code> (synchronization primitives -- mutexes, channels)</li> <li><code>embassy-net</code> (network abstraction)</li> </ul> </li> <li> <p><code>smoltcp</code>: runtime-agnostic/userspace network stack</p> </li> </ul> <p>The holy grail is to be easily able to develop a portable embedded program (as in: nearly the whole body of the program is <em>entirely</em>, character-by-character, identical on an ESP32 and an RP2040) that uses an async executor to schedule network I/O, disk/flash I/O, <em>and</em> peripheral access.</p> <p>In the scheme of things, we're close, with Rust. <code>smoltcp</code> is parametric over both its physical medium (Ethernet, IP packets (virtual medium), etc.) <em>and</em> the implementation -- I can write a new raw socket interface and it will work fine. <code>embassy-net</code> and <code>embedded-nal</code> are themselves generic over their tcp and udp socket types -- even the DNS implementation. <code>embedded-hal</code> gets us peripheral bus access that is abstracted from the MCU -- you can actually write a generic driver in Rust against a clearly- and well-defined interface.<sup class="footnote-reference"><a href="#2">2</a></sup></p> <p>I mention all of this because I received a painstakingly clear picture of where things stand for the ESP32C3. Things <em>are</em> close, but the edges are still very rough. It is posssible to write a program that uses an asynchronous executor to do HTTP requests and blink LEDs and at least try to connect to an MQTT broker all at the same time. However, the HTTP requests take tens of seconds each, TLS doesn't work, and I never did get the MQTT broker to connect.</p> <p>The fact that it works at all, however, gives me hope -- that such a thing works at all means that this highly distributed and mutually-abstracted implementation is <em>mostly right</em>.</p> <p>Anyway, some other things I ran into:</p> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-storage z-type z-rust">const</span> <span class="z-constant z-other z-rust">HEAP_SIZE</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-storage z-type z-rust">usize</span> <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-constant z-numeric z-integer z-decimal z-rust">64</span> <span class="z-keyword z-operator z-arithmetic z-rust">*</span> <span class="z-constant z-numeric z-integer z-decimal z-rust">1024</span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">static</span> <span class="z-storage z-modifier z-rust">mut</span> <span class="z-constant z-other z-rust">HEAP_MEM</span><span class="z-punctuation z-separator z-rust">:</span> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-storage z-type z-rust">u8</span><span class="z-punctuation z-separator z-rust">;</span> <span class="z-constant z-other z-rust">HEAP_SIZE</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span> <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-constant z-numeric z-integer z-decimal z-rust">0</span><span class="z-storage z-type z-numeric z-rust">u8</span><span class="z-punctuation z-separator z-rust">;</span> <span class="z-constant z-other z-rust">HEAP_SIZE</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-annotation z-rust"><span class="z-punctuation z-definition z-annotation z-rust">#</span><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-variable z-annotation z-rust">global_allocator</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">static</span> <span class="z-constant z-other z-rust">HEAP</span><span class="z-punctuation z-separator z-rust">:</span> Heap <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">Heap<span class="z-punctuation z-accessor z-rust">::</span></span>empty<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">main</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span>, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-constant z-other z-rust">HEAP</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">init</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-constant z-other z-rust">HEAP_MEM</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_ptr</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> <span class="z-keyword z-operator z-rust">as</span> <span class="z-storage z-type z-rust">usize</span><span class="z-punctuation z-separator z-rust">,</span> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> <span class="z-constant z-other z-rust">HEAP_MEM</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">len</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> elided </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p>We're looking at the initialization of my heap data structure and its backing memory. I expected this to work, but in fact I was getting clear memory corruption (behavior-dependent, occasional-crashes, store/load exception messages, etc.). Thought it could be the stack, but it didn't actually seem to be.</p> <p>The actual solution to the problem was this:</p> <pre data-lang="ld" class="language-ld z-code"><code class="language-ld" data-lang="ld"><span class="z-source z-linker"><span class="z-keyword z-control z-linker">SECTIONS</span> { </span><span class="z-source z-linker"> <span class="z-variable z-other z-linker">.heap</span> (<span class="z-variable z-other z-linker">NOLOAD</span>) : <span class="z-keyword z-control z-linker">ALIGN</span>(<span class="z-constant z-numeric z-integer z-linker">4</span>) { </span><span class="z-source z-linker"> <span class="z-variable z-other z-linker">__heap_start</span> = <span class="z-variable z-language z-linker">.</span>; </span><span class="z-source z-linker"> <span class="z-variable z-language z-linker">.</span> += <span class="z-constant z-numeric z-integer z-linker">128K</span>; </span><span class="z-source z-linker"> <span class="z-variable z-other z-linker">__heap_end</span> = <span class="z-variable z-language z-linker">.</span>; </span><span class="z-source z-linker"> } &gt; <span class="z-variable z-other z-linker">RWDATA</span> </span><span class="z-source z-linker">} </span><span class="z-source z-linker"><span class="z-variable z-other z-linker">INSERT</span> <span class="z-variable z-other z-linker">AFTER</span> <span class="z-variable z-other z-linker">.stack_end</span>; </span></code></pre> <pre data-lang="rust" class="language-rust z-code"><code class="language-rust" data-lang="rust"><span class="z-source z-rust"><span class="z-keyword z-other z-rust">extern</span> <span class="z-string z-quoted z-double z-rust"><span class="z-punctuation z-definition z-string z-begin z-rust">&quot;</span>C<span class="z-punctuation z-definition z-string z-end z-rust">&quot;</span></span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">static</span> __heap_start<span class="z-punctuation z-separator z-rust">:</span> <span class="z-storage z-type z-rust">u8</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">static</span> __heap_end<span class="z-punctuation z-separator z-rust">:</span> <span class="z-storage z-type z-rust">u8</span><span class="z-punctuation z-terminator z-rust">;</span> </span></span><span class="z-source z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-annotation z-rust"><span class="z-punctuation z-definition z-annotation z-rust">#</span><span class="z-punctuation z-section z-group z-begin z-rust">[</span><span class="z-variable z-annotation z-rust">global_allocator</span><span class="z-punctuation z-section z-group z-end z-rust">]</span></span> </span><span class="z-source z-rust"><span class="z-storage z-type z-rust">static</span> <span class="z-constant z-other z-rust">HEAP</span><span class="z-punctuation z-separator z-rust">:</span> Heap <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-path z-rust">Heap<span class="z-punctuation z-accessor z-rust">::</span></span>empty<span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span><span class="z-source z-rust"> </span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-function z-rust"><span class="z-storage z-type z-function z-rust">fn</span> </span><span class="z-entity z-name z-function z-rust">main</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-begin z-rust">(</span></span><span class="z-meta z-function z-rust"><span class="z-meta z-function z-parameters z-rust"><span class="z-punctuation z-section z-parameters z-end z-rust">)</span></span></span></span><span class="z-meta z-function z-rust"> <span class="z-meta z-function z-return-type z-rust"><span class="z-punctuation z-separator z-rust">-&gt;</span> <span class="z-meta z-generic z-rust"><span class="z-support z-type z-rust">Result</span><span class="z-punctuation z-definition z-generic z-begin z-rust">&lt;</span><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-punctuation z-section z-group z-end z-rust">)</span>, <span class="z-keyword z-operator z-rust">_</span><span class="z-punctuation z-definition z-generic z-end z-rust">&gt;</span></span></span> </span><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-modifier z-rust">unsafe</span> <span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-begin z-rust">{</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> start <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>__heap_start</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_ptr</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-storage z-type z-rust">let</span> end <span class="z-keyword z-operator z-assignment z-rust">=</span> <span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span><span class="z-keyword z-operator z-bitwise z-rust">&amp;</span>__heap_end</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">as_ptr</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span></span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> <span class="z-constant z-other z-rust">HEAP</span><span class="z-punctuation z-accessor z-dot z-rust">.</span><span class="z-support z-function z-rust">init</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-begin z-rust">(</span>start<span class="z-punctuation z-separator z-rust">,</span> end <span class="z-keyword z-operator z-arithmetic z-rust">-</span> start</span><span class="z-meta z-group z-rust"><span class="z-punctuation z-section z-group z-end z-rust">)</span></span><span class="z-punctuation z-terminator z-rust">;</span> </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"><span class="z-meta z-block z-rust"> </span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> </span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"> <span class="z-comment z-line z-double-slash z-rust"><span class="z-punctuation z-definition z-comment z-rust">//</span> elided </span></span></span></span><span class="z-source z-rust"><span class="z-meta z-function z-rust"><span class="z-meta z-block z-rust"></span><span class="z-meta z-block z-rust"><span class="z-punctuation z-section z-block z-end z-rust">}</span></span></span> </span></code></pre> <p>Theoretically, <code>HEAP_MEM</code> in my first example should have statically allocated the space I requested, meaning no other symbol should have intruded upon it. If the problem was running out of space, the heap data structure would fail mallocs, and I'd seen that in the logs for other reasons before, so I had been fairly confident that wasn't happening.</p> <p>Instead, I'm pretty sure this was UB -- there was nowhere <code>HEAP_MEM</code> was actually getting <em>used</em> for anything, so the Rust compiler wasn't able to reason about it and simply didn't reserve the memory in <code>.bss</code>. Specifically, <code>HEAP_MEM.as_ptr() as usize</code> totally erases any association to the backing array by degrading to an integer type. Hence, <code>malloc</code>s were stomping over other memory.</p> <p>I'm fairly confident in this because after using the linker to reserve the space, the problem went away -- no more corruption.</p> <h3 id="defmt"><code>defmt</code></h3> <p>This is a nice embedded logging utility available in Rust that I discovered as part of this implementation. It's essentially a very aggressive string-interner that shoves the interned strings <em>into a debug section</em> and replaces them in the actual binary with their indices -- when the binary gets flashed, there's very little overhead from logging (code size, or runtime memory/I/O). You need the original binary in order to decode the logs, but <code>defmt</code> comes with a tool <code>defmt-print</code> that you can pipe them through. It supports interpolation and does compression on top of that, too.</p> <h2 id="elixir-erlang-on-atomvm">elixir / erlang on <a href="https://github.com/atomvm/AtomVM">atomvm</a></h2> <p>I have mixed feelings about erlang/elixir because of their typing-indecisiveness. They don't give you many tools, as languages, to prove correctness -- in an environment like erlang that's intentionally designed to encourage dynamism of behavior, this spooks me more than a little bit.</p> <p>However, I also in my heart believe that actor systems are essentially correct as a way to build distributed systems (at least up to hard performance requirements). WiFi-enabled microcontrollers represent an environment that is not terribly computationally demanding (if you really cared about power (hence computational overhead), you wouldn't be using WiFi) and could benefit from this model.</p> <p>Maybe most attractive here is that all data in Erlang is represented as a single inductive type (<code>term</code>), which can be binary-encoded and decoded with a single function call (<code>:erlang.term_to_binary</code>, <code>:erlang.binary_to_term</code>) -- you get this for free, for all data, always -- so the overhead of communicating to remote nodes is very low. Similarly it's two function calls to send a UDP packet:</p> <pre data-lang="elixir" class="language-elixir z-code"><code class="language-elixir" data-lang="elixir"><span class="z-source z-elixir"><span class="z-meta z-sequence z-tuple z-elixir"><span class="z-punctuation z-section z-sequence z-begin z-elixir">{</span><span class="z-constant z-other z-symbol z-elixir"><span class="z-punctuation z-definition z-constant z-elixir">:</span>ok</span><span class="z-punctuation z-separator z-sequence z-elixir">,</span> sock<span class="z-punctuation z-section z-sequence z-end z-elixir">}</span></span> <span class="z-keyword z-operator z-assignment z-elixir">=</span> <span class="z-constant z-other z-symbol z-elixir"><span class="z-punctuation z-definition z-constant z-elixir">:</span>gen_udp</span><span class="z-punctuation z-separator z-method z-elixir">.</span>open<span class="z-punctuation z-section z-function z-elixir">(</span>port<span class="z-punctuation z-section z-function z-elixir">)</span> </span><span class="z-source z-elixir"><span class="z-constant z-other z-symbol z-elixir"><span class="z-punctuation z-definition z-constant z-elixir">:</span>gen_udp</span><span class="z-punctuation z-separator z-method z-elixir">.</span>send<span class="z-punctuation z-section z-function z-elixir">(</span>sock<span class="z-punctuation z-separator z-object z-elixir">,</span> ip<span class="z-punctuation z-separator z-object z-elixir">,</span> port<span class="z-punctuation z-separator z-object z-elixir">,</span> data<span class="z-punctuation z-section z-function z-elixir">)</span> </span></code></pre> <p>The socket then even <em>sends data to your processes as messages</em>:</p> <pre data-lang="elixir" class="language-elixir z-code"><code class="language-elixir" data-lang="elixir"><span class="z-source z-elixir"><span class="z-meta z-module z-elixir"><span class="z-keyword z-control z-module z-elixir">defmodule</span> <span class="z-entity z-name z-class z-elixir">MyModule</span> <span class="z-keyword z-control z-module z-elixir">do</span></span> </span><span class="z-source z-elixir"> <span class="z-keyword z-control z-elixir">use</span> <span class="z-entity z-name z-class z-elixir">GenServer</span> </span><span class="z-source z-elixir"> </span><span class="z-source z-elixir"><span class="z-comment z-line z-number-sign z-elixir"> <span class="z-punctuation z-definition z-comment z-elixir">#</span> ... elided ... </span></span><span class="z-source z-elixir"> </span><span class="z-source z-elixir"><span class="z-meta z-function z-elixir"> <span class="z-keyword z-control z-module z-elixir">def</span> <span class="z-entity z-name z-function z-public z-elixir">handle_info</span><span class="z-punctuation z-definition z-parameters z-elixir">(</span><span class="z-meta z-sequence z-tuple z-elixir"><span class="z-punctuation z-section z-sequence z-begin z-elixir">{</span><span class="z-constant z-other z-symbol z-elixir"><span class="z-punctuation z-definition z-constant z-elixir">:</span>udp</span><span class="z-punctuation z-separator z-sequence z-elixir">,</span> sock<span class="z-punctuation z-separator z-sequence z-elixir">,</span> addr<span class="z-punctuation z-separator z-sequence z-elixir">,</span> port<span class="z-punctuation z-separator z-sequence z-elixir">,</span> packet<span class="z-punctuation z-section z-sequence z-end z-elixir">}</span></span><span class="z-punctuation z-section z-function z-elixir">)</span> <span class="z-keyword z-control z-module z-elixir">do</span></span> </span><span class="z-source z-elixir"><span class="z-comment z-line z-number-sign z-elixir"> <span class="z-punctuation z-definition z-comment z-elixir">#</span> ... elided ... </span></span><span class="z-source z-elixir"> <span class="z-keyword z-control z-elixir">end</span> </span><span class="z-source z-elixir"><span class="z-keyword z-control z-elixir">end</span> </span></code></pre> <p>The model is really so straightforward -- it captures something deep.</p> <h3 id="atomvm">atomvm</h3> <p>I had come across AtomVM probably a couple of years ago looking at embedded projects and wanted to try it but never found a fit. I saw it supported ESP32 and figured I'd give it a shot for this week.</p> <p>This was not easy. AtomVM is alpha-readiness, open-source software and to my knowledge not commercially-supported. It builds off of esp-idf (discussed above), which I luckily already had installed. Notionally, it also supports esp32c3 (even though they mostly explicitly talk about the original esp32), but the installer images don't work if you follow their instructions directly.</p> <p>For some background, AtomVM is a binary firmware image that you can load into flash. It won't do anything, though, unless you put a <code>.avm</code> (AtomVM precompiled Erlang bytecode) image at a different flash offset. Then (after a reboot) the base image loads the bytecode and runs it -- you're off to the races.</p> <p>Now that we have this context, we can get to the incorrect instructions. You may imagine it's critical that you load each of these images at the correct offset so that the first one is picked up by the Espressif bootloader and the second one is picked up by the first. The base offset for the esp32 is 0x1000. For all other models of esp (as far as I can tell) there is no offset -- load to 0x0. The default tooling and all the instruction say to put the image at 0x1000.</p> <p>I didn't figure out this was the problem until I had cloned atomvm and fully scratch-rebuilt freshest master, where the <code>flashimage.sh</code> script for the esp32c3 platform actually shows (once you build it) that its offset is 0x0.</p> <p>After I did this I was able to run erlang/elixir on the MCU. This was nice, but it was followed up by several hours of tracing back exactly how AtomVM differs from BEAM/OTP (the canonical erlang distribution, runtime, and standard library).</p> <p>There were many subtle features I discovered here, like that the AtomVM folks didn't implement <code>:gen_server.start_link/4</code>, but they <em>did</em> implement <code>:gen_server.start_link/3</code> and the name registry. You can call <code>:gen_server.start_link/3</code> and then call <code>:erlang.register/2</code> with the same name you would have passed to <code>start_link/4</code>, and it's as if you had called <code>start_link/4</code>. Why there isn't just a <code>start_link/4</code> perhaps I'll never know.</p> <h3 id="elixir">elixir</h3> <p>Elixir seems to mostly have been added to AtomVM as an afterthought. There's almost no overhead to doing so, as the bytecode is the same, but almost none of the Elixir standard library works. This is fine, as it turns out, as most of the Elixir standard library is just an opinionated wrapper around the Erlang core.</p> <p>In the abstract, I knew this, but I hadn't been so aware of how little extra Elixir gives you until I had to go without most of it. It's mostly trying to be magical and that ends up being confusing -- I gained a much clearer appreciation for what the "actual" Erlang API looks like as a part of this.</p> <p>I did some patching by copy-pasting parts of the Elixir standard library into my project, then stripping out anything not supported by the AtomVM runtime. As a result, I have my own <code>GenServer</code> and <code>Supervisor</code> that work on AtomVM, though I ended up just using <code>:supervisor</code> directly from erlang because the implementation is really not complete on the AtomVM side -- there's a lot hard-coded -- so adapting <code>Supervisor</code> to all possible use-cases is a pain.</p> <h3 id="result">result</h3> <p>The final functional result for this implementation are some indicator LEDs that show the WiFi status (and NTP -- AtomVM will grab this for you as part of the network configuration), plus one that's controlled over a UDP socket. I wrote a UDP client also in Elixir (it's pretty much the 2 lines from above) and they just pass terms directly via binary. Really the easiest RPC I've ever done, and it'd be trivial to wire more actors into the system.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;blinky.29c7197f9e4df6c1.jpg"> </div> <div class="footnote-definition" id="1"><sup class="footnote-definition-label">1</sup> <p><em>crate</em> = Rust package.</p> </div> <div class="footnote-definition" id="2"><sup class="footnote-definition-label">2</sup> <p>Note: by contrast, I do <em>not</em> consider Arduino to be clean or well-defined.</p> </div> 2023-09-20T00:00:00+00:00 2023-09-20T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/final-project-concept/ <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chair.183debeec9fad55d.jpg"> </div> <p>Current idea for my final project is a flight simulator cockpit ("simpit"). I enjoy flying in flight sims, both military (e.g., <a href="https://www.digitalcombatsimulator.com/en/">DCS World</a>, <a href="https://vtolvr.bdynamicsstudio.com/">VTOL VR</a>) and civilian (<a href="https://www.flightsimulator.com/">MSFS 2020</a>). I already have gear from <a href="https://virpil-controls.us.com/">Virpil Controls</a> -- specifically a flight stick, throttle, and rudder pedals. I also have a <a href="https://store.steampowered.com/valveindex">Valve Index</a> VR headset (flight sims are in my opinion one of the best applications for VR currently).</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;flightstick.369326e58a4d85bb.jpg"> </div> <p><em>Flight stick</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;throttle.b42615d0e66fe92d.jpg"> </div> <p><em>Throttle</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;rudder_pedals.7e7f6f6acaa6d410.jpg"> </div> <p><em>Rudder pedals</em></p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;vr_headset.eef48c95c8673776.jpg"> </div> <p><em>VR Headset</em></p> <h2 id="major-limitations">major limitations</h2> <p>I don't fly sims as much as I would like because:</p> <ul> <li> <p>setup and teardown overhead is high</p> <ul> <li>clamp flight stick and throttle to my desk</li> <li>secure rudder pedals with paracord</li> <li>get VR headset back out, plugged in, and snake umbilical so it's out of the way</li> <li>this totally interferes with my normal usage of my desk, so i need to tear the whole setup down after every time i use it</li> </ul> </li> <li> <p>my chair is the opposite of ergonomic for VR and flight sims</p> <ul> <li>wheels are not helpful for maintaining consistent body positioning in VR and relative to controls</li> <li>anatomics of rudder pedals raised off of the floor combined with a normal chair mean I end up closer to balancing on my tailbone than sitting flat</li> <li>I sometimes need to use a mouse and keyboard for input and I have to lean over my controls and sit on the edge of my seat to do this. Not ergonomic -- causes muscle aches / mild strains if I do it a lot.</li> </ul> </li> <li> <p>controls positioning isn't quite correct</p> <ul> <li>rudder pedals move on me all the time / I can't push very hard on them</li> <li>controls shift a bit each time I set it up -- big deal in VR</li> </ul> </li> </ul> <h3 id="addressing-limitations">addressing limitations</h3> <p>The core of the project (what I need most) would address these limitations with:</p> <ul> <li>an ergonomic seat (reclined, probably adjustable, correct relationship to all controls, ideally easy to get in and out of)</li> <li>solid control mounts that don't move relative to the seat</li> <li>a spot to keep my VR headset that is easily accessible while sitting, but isn't in the way</li> <li>should fit in one spot I have picked out in my room next to my PC (measurement pending)</li> <li>a spot for a mouse and keyboard that's easily accessible from the seat <em>and</em> doesn't interfere with the controls</li> </ul> <h2 id="additional-desiderata">additional desiderata</h2> <h3 id="more-physical-controls">more physical controls</h3> <p>VR is great for visualization and immersion. It gives a much better feel for the dynamics of flight when you can see the whole world moving around you (including some peripheral vision) and you're not just staring through a clunky-to-move player camera PoV. A VR perspective enables you to take glances and quickly scan the ground or a part of the sky.</p> <p>However, <em>controlling</em> planes using VR interaction metaphors is a poor experience. Typically, VR flight sim controls involve pointing at virtual targets with the hand controllers and clicking. This is difficult in flight sims because the cockpits being simulated are very dense -- it takes careful aim and a steady hand to select exactly the button you wanted to click. Some form of haptic feedback is usually provided when your controller target changes (slight bump), but this falls drastically short of the real-world ability to find physical controls by touch memory and relative position only.</p> <p>For these reasons, I bind as much as possible onto the physical controls I already have, but there are still a lot of inputs remaining that I have to actuate using VR controls. Illustratively, a typical startup sequence involves 5 minutes of carefully lining up my controller at half of the buttons in the cockpit and trying to get only the relevant virtual switches and buttons to actuate.</p> <p>High-button-density controls like OSBs (on-screen buttons) around multi-function displays (MFDs):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;mfd.c0739f1aec95b8fe.jpg"> </div> <p>are also not worth mapping to HOTAS controls both because there are a lot of them (typ. 20 per MFD, x 2 or 3 MFDs) and because they rely on their physical position around the display to supply semantic context, which is totally absent if you move the buttons to a different control.</p> <p>I'm planning on making two or three MFDs with dummy screens (for VR use -- buttons only, functional screens not required). I intend to make the dummy screen a modular swap for a 7" square screen (typical of these MFDs) in case I want this in the future.</p> <p>I'm considering adding one or two additional boxes with button and switch arrays to augment what I already have.</p> <h3 id="portability">portability</h3> <p>I am aiming to make this setup portable. As a result, I want it to break down into small modular pieces interconnected with consistent power and data buses. If possible, I will do everything with USB-C (using USB-PD if required).</p> <p>However, I still want it to feel solid -- I will be investigating significant use of tensile members to keep the structure rigid.</p> <p>I expect it will be straightforward to produce low-part-count control mounts that bolt directly to the rest of the setup, so the main concern here is the chair. Design ideas are still percolating, but probably I will make it possible to fully disassemble the joints that make the chair adjustable, which will let it break down in relatively small pieces.</p> <h2 id="prior-art">prior art</h2> <p>There is <em>extensive</em> prior art amongst the flight sim hobbyist community for building simpits. While I will draw at a high level here for inspiration and possible approaches, I will most likely directly make use of several existing systems host-side to get external signals into the flight sims. Most notably: <a href="https://dcs-bios.readthedocs.io/en/latest/">DCS-BIOS</a>.</p> <h2 id="renders">renders</h2> <p>Below is a render of what this project might look like as a combined system:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;chair.183debeec9fad55d.jpg"> </div> <p>This image was produced directly from the CAD assembly (linked below), exported as an STL and rendered in Blender using Cycles.</p> <h2 id="design-files">design files</h2> <p>Design files can be found <a href="https://blog.npry.dev/class/htm/final-project-concept/design_files.zip">here</a>.</p> 2023-09-20T00:00:00+00:00 2023-09-20T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/laser/ <p>Laser cutter: 30W GCC</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;box_multiple_sizes.6365c56bd965a63a.jpg"> </div> <p><em>Final result</em></p> <h2 id="settings">settings</h2> <p>Using the suggested settings as a baseline, I arrived at the following refined numbers for 1/8" cardboard:</p> <table><thead><tr><th>speed</th><th>2.3%</th></tr></thead><tbody> <tr><td>power</td><td>100</td></tr> <tr><td>ppi</td><td>220</td></tr> </tbody></table> <p>The largest item causing variance in cut quality was focus -- my cardboard sheet was bowed up, causing me to lose focus in the middle of the sheet, leading to a black burn on the upper surface blooming from the cut location and loss of effective cut power. I noticed this by comparison as I was watching Cayden and Lancelot cut their projects.</p> <h2 id="kerf-characterization-part-1">kerf characterization (part 1)</h2> <p>I initially tried to measure kerf with arrays of interlocking fingers of increasing kerf compensations.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fit_test_2.b88a9fa67ef67d2e.jpg"> </div> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;fit_test.a53441f6e4c448ff.jpg"> </div> <p>I measured the thickness of the cardboard using a set of calipers and found that it was approximately 4.15mm thick. The finger widths thus started at 4.15mm and increased in 0.2mm increments. I anticipated that this would make the first two indices too small, as Neil told us that the beam waist was in the ballpark of 0.010". 0.1mm is approximately 0.004", so I would have expected an interference fit between indices 2 and 3. However, index 1 fit perfectly (no kerf compensation).</p> <p>I realized the error of my ways after the fact as I was building my project: the precision of my measurement was reliant on my ability to measure cardboard thickness precisely with calipers, and on cardboard having a consistent thickness in the first place. I remedied this later.</p> <h2 id="project-summary-or-kerf-characterization-part-2">project summary (or: kerf characterization part 2)</h2> <p>I made parametric cardboard holders. Their function is simply to elevate an object. I started out making small boxes using box-jointed edges and realized that (obviously) they would not hold with just a box joint (I'm used to using adhesive).</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;kerf_good_fit.2008fd13b0090e20.jpg"> </div> <p>This, however, let me dial in my kerf, as the precision in the box joint is entirely in the vertical axis and not dependent on the thickness of the cardboard at all. I binary searched, printing repeated joints, and arrived at a kerf compensation of 0.15mm (= approx 0.006"), giving an interference fit inasmuch as one can be said to exist in cardboard.</p> <h2 id="wedged-joints">wedged joints</h2> <p>Given that the joint was not going to hold as-is, I added a joint (topmost on the edge) that could accept a wedge.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;small_box_no_wedge.93123f54e60165b6.jpg"> </div> <p>Wedges installed:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;box_wedge_final.711957b177d94065.jpg"> </div> <p>The complete support is relatively sturdy for what it is. Holding a power supply on my desk:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;box_holding_power_supply.5cebbd540415ca45.jpg"> </div> <p>I don't believe the wedges are actually in any significant shear loading while the structure is bearing weight -- I think the increased friction of the joint as a result of this construction is actually what's providing most of the stability.</p> <h2 id="cutting-wedges">cutting wedges</h2> <p>The wedges were difficult to cut, small as they were:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;wedge_wrong_axis.c5b53c6d7836cb1f.jpg"> </div> <p>The above wedge failed because it was cut <em>along</em> the axis of the cardboard corrugations and could easily twist off of the single line of glue. I soon realized this and changed them to be cut across the corrugations.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;wedge_good_axis.866c57af3f78fb6e.jpg"> </div> <p>I still had some failures this way due to delamination, but under 20%.</p> <p>Originally, I was cutting the wedges one-by-one in left-over areas on the cardboard between the walls, but I decided to develop a way to pack them more densely.</p> <p>First, I simply went for a dense packing in an array:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;wedges_array.574705ad27c7046f.jpg"> </div> <p>Then I built a "sprue tree" out of cardboard to retain several wedges as one complete unit that could be extracted from the laser cutter more easily.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;wedges_sprue.49962245e6b6db24.jpg"> </div> <p>Surprisingly for how thin the connecting member is, these came out without tearing any of the "sprues" very consistenly.</p> <h2 id="parametricity">parametricity</h2> <p>Adjustable parameters:</p> <ul> <li>Height</li> <li>Width</li> <li>Leg height</li> <li>Number of box fingers</li> <li>Cardboard thickness</li> </ul> <p>The cross-member thickness is a proportion of the width or height of the relevant direction.</p> <p>A small box and a big box patterned from the same design file:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;box_multiple_sizes.6365c56bd965a63a.jpg"> </div> <h2 id="corel-draw-tricks">corel draw tricks</h2> <p>The best way I could figure out to use Corel Draw was as follows:</p> <ul> <li>Set the "paper" as the full size of the bed</li> <li>Pick a color that is your no-cut color (I picked blue) and configure the printer not to cut it (uncheck vector, raster in the color configuration)</li> <li>Draw a rectangle within the bed outline that is the size of your cardboard (colored no-cut) as a reference</li> <li><em>Keep working off of this one file</em>: each time you print a part, mark it no-cut but leave it in-place. Now you know what parts of the sheet you've used and can squeeze in other parts quite precisely.</li> </ul> <p>Additional note: there is a palette of recent colors in the bottom left. Right-click a color to set the currrently-selected curve to that color (left-click is fill).</p> <h2 id="design-files">design files</h2> <p><a href="https://blog.npry.dev/class/htm/laser/laser_design_files.zip">Here</a>.</p> 2023-09-20T00:00:00+00:00 2023-09-20T00:00:00+00:00 Nathan Perry https://blog.npry.dev/class/htm/vinyl/ <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;window.a4501e5589ff5f82.jpg"> </div> <p>I cut this window sticker with the Roland vinyl cutter. The pattern I used was the last stanza of The Lord of the Rings' Ring Poem:</p> <blockquote> <p><em>One ring to rule them all, one ring to bind them</em></p> <p><em>One ring to bring them all and in the darkness bind them</em></p> </blockquote> <p>or as more directly rendered in the Black Speech:</p> <blockquote> <p><em>Ash nazg durbatulûk, ash nazg gimbatul</em></p> <p><em>Ash nazg thrakatulûk agh burzum-ishi krimpatul</em></p> </blockquote> <p>or finally the Black Speech in the Sindarin <em>tengwar</em> alphabet (actual cut pattern):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;pattern.e019944681b1d8ce.jpg"> </div> <p>The circular Ring Poem pattern is common in Lord of the Rings art, but rather than use something preexisting, I made the figure myself in Adobe Illustrator using the venerable <a href="https://www.dafont.com/tengwar-annatar.font">Tengwar Annatar font</a> (input method documented <a href="https://www.elfico.com.br/wp-content/uploads/2013/12/tngandoc.pdf">here</a>).</p> <hr /> <p><strong><em>Tengwar</em> notes</strong></p> <ul> <li>A <em>tengwa</em> is a single character (<em>tengwar</em> being the plural) representing a consonant</li> <li><em>Tehtar</em> (singular <em>tehta</em>) are diacritics that appear above and below <em>tengwar</em> representing vowels</li> </ul> <p><strong>Typography notes</strong></p> <ul> <li>Vertical character stems are known as <em>ascenders</em> or <em>descenders</em> (depending on direction)</li> </ul> <hr /> <h2 id="corel-draw-import">corel draw import</h2> <p>I followed the instructions for the Roland vinyl cutter and ran into two issues.</p> <p>First, DXF v2018, the default DXF export option for current versions of Illustrator is (unsurprisingly) not valid in our version of Corel Draw (2017). Exporting as v2013 solved this problem.</p> <p>Secondly, my image contained self-intersecting segments from overlapping characters:</p> <table><thead><tr><th> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;intersect.cfa19dcfb673cb5f.jpg"> </div> </th></tr></thead><tbody> <tr><td>Selected <em>tehta</em> (blue) overlaps unselected (black).</td></tr> </tbody></table> <p>Cutting the image with these self-intersections would have produced undesired segmentation in the final pattern. I eliminated these intersections by using the path union tool in Illustrator.</p> <h2 id="sample-pattern">sample pattern</h2> <p>I cut a sample piece first to test my process using a section of the final pattern. I selected the sample pattern to intentionally include many of the elements I expected would be most recalcitrant (thin, long ascenders, disconnected <em>tehtar</em>, looping/spiral elements), to build confidence that the full pattern would be feasible.</p> <p>I cut at 20 mm/second and 80 grams-force of pressure (default recommendation on the Roland). I found that 80 grams-force was slightly too light -- I was having to fight to shear the vinyl in some sections as I was weeding it. As a result, I increased the pressure to 85 grams-force for the final cut.</p> <p>Just as I was starting to weed:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weeding.1b96602c79c5b992.jpg"> </div> <p>You can see that I subdivided the vinyl I needed to weed using a mat knife in order to enable smaller, individually-completable weeding actions in which I could control.</p> <p>Weeding complete:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weeded.17be27cfbe7b0b0f.jpg"> </div> <p>I lost a portion of the /a/ <em>tehta</em> on the left -- it should look like the one in the middle (three approximately-vertical marks). I wasn't careful touched the adhesive with my finger -- it lost enough stick as a result that it moved significantly when I placed it back down and loosely stuck to the middle mark. I didn't want to lose this one too, so I left them stuck together.</p> <p>On the transfer:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;transferred.20b1caa245246719.jpg"> </div> <p>I peeled the backing right after applying it to ensure I had applied enough pressure and that there wouldn't be any issues with the difficult pattern elements. There weren't, but I should have either taken the sample to completion and applied it to glass or not removed the backing to preserve the adhesive. I went halfway instead, and regret doing so (though it didn't result in any adverse consequences in this case).</p> <h2 id="full-pattern">full pattern</h2> <p>At this point I started on the complete pattern. As far as I could find, the shop was out of black vinyl (the color I wanted) except for a few strips and a ~300x400mm sheet with a crease in it that caused the vinyl to bulge. You can see this crease/bulge here (after I cut the pattern):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;bulge.51d03cea7f964e98.jpg"> </div> <p>I knew this would cause some difficulties, but I tried it anyway. An additional feature of this full cut that I didn't see on the sample pattern was scoring apparently due to the knife dragging on the vinyl between pattern elements. I suspect this is because the vinyl was not very flat.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;scoring.62f9f4b3b25f5031.jpg"> </div> <p>In the previous two images you can see that I had started to segment the non-pattern vinyl to make easier peels as I had done in the sample. This image provides some more detail on how I did this:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;segmentations.a861e32e43a7822e.jpg"> </div> <p>I cut a ring inside the <em>tengwar</em> descenders, then I separated the outside excess vinyl from the inside but cutting between characters. I made an cut from the tip of each descender and ascender to the inner ring or the outer edge of the vinyl, respectively. This was to ensure that I could pull each vinyl segment as much aligned with the axis of each ascender / descender as possible, to avoid these high aspect-ratio elements tearing or deforming.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;tehtar_cutouts.f70de3d105ac4849.jpg"> </div> <p>This image shows the weeding partially done, and showcases protective cells I cut around each <em>tehta</em>. This technique allowed me to peel the bulk of the vinyl fairly quickly by avoiding these delicate, high-detail areas. I peeled them at the very end.</p> <p>Here is a more zoomed out shot of the state of the weeding at this point (interior mostly complete):</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weeding_mostly_done.80e9b7f94bf50dac.jpg"> </div> <p>I had weeded my sample using a pair of tweezers, but I discovered as I was weeding the complete pattern that I prefer to use the sharp corner of a mat knife to catch the vinyl. This gave me much more dexterity, and I almost never peeled anything I didn't mean to.</p> <p>Fully weeded:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;weeding_done.93e6d404d5c9d82b.jpg"> </div> <p>Transfer applied:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;transfer.b9bd1d642cb2550b.jpg"> </div> <p>I used the side of the mat knife (retracted) to apply heavy pressure on the whole pattern to ensure it would all pull off of the backing.</p> <h2 id="sample-pattern-window-application">sample pattern window application</h2> <p>At this point, I still had the sample pattern with its backing removed. I went to the window I wanted to transfer to and made a first try with the sample pattern on the other pane.</p> <p>Sample applied:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;window_transfer.474987e95bc520af.jpg"> </div> <p>I also rubbed this with the side of the mat knife to ensure the vinyl was as well-adhered as possible to the window.</p> <p>I had no issues peeling the transfer -- I went very slowly and used the mat knife to catch anything that wanted to lift. I varied my peel angle to minimize lifting torque (generally aiming to peel <em>along</em> the axis of the typographic elements).</p> <p>Sample transfer peeled:</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;window.cb4bd09945c040dd.jpg"> </div> <h2 id="full-pattern-window-application">full pattern window application</h2> <p>I then prepped the window for the full pattern by cleaning the application area with isopropyl alcohol in an attempt to improve adhesion.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;window_cleaning.c81d167782d6d237.jpg"> </div> <p>Approach was the same as the sample -- I went slow and carefully ensured each pattern element released from the transfer cleanly.</p> <div class="centered_image"> <img src="https:&#x2F;&#x2F;blog.npry.dev&#x2F;processed_images&#x2F;window.a4501e5589ff5f82.jpg"> </div> <p>To my knowledge, I didn't lose any of the tiny <em>tehtar</em>, and the ascenders/descenders are in-place mostly unmolested.</p> <h2 id="design-files">design files</h2> <p><a href="https://blog.npry.dev/class/htm/vinyl/vinyl_design_files.zip">Here</a>.</p> 2023-01-20T00:00:00+00:00 2024-08-10T00:00:00+00:00 Nathan Perry https://blog.npry.dev/resenv/antrelay/ <p><a href="https://ironman-007.github.io/FZ-portfolio/astroant.html">Fangzheng's AstroAnt</a> is going to the moon:</p> <ul> <li>Aboard <a href="https://www.lunaroutpost.com/rovers">Lunar Outpost's MAPP Rover</a>: <ul> <li>Aboard Intuitive Machines' <a href="https://www.intuitivemachines.com/missions">IM-2 lander mission</a>: <ul> <li>Launched by a <a href="https://www.spacex.com/vehicles/falcon-9/">Falcon 9</a> near the end of 2024</li> </ul> </li> </ul> </li> </ul> <p>I wrote a software payload called <code>antrelay</code> which runs onboard the MAPP-1 rover to control the AstroAnt's motion, decode its telemetry downlink, and ensure recovery from unexpected errors.</p> <p>Block diagram and more complete descrption forthcoming.</p> <!-- TODO: block diagram !-->