Karl Herrick

A technologist and web developer | Posts about technology encountered along the journey.

Fast Traxx Pi

I thought it was good time to revisit trying to control an RC car’s handheld remote, so I returned to the community assistance I first started at and gave it a try. In the end, I just had to wire up some transistors to the remote control as well as a few resistors leading back to the GPIO pins on the Pi.

The software side is fairly straightforward as it implements basic driving functionality and requires only a few Node.js dependencies (the rpio library and an experimental one to handle keyup and keydown events). Running the main script from the github repo sets up four pins as outputs, and are triggered when the arrow keys are pressed. Ctrl+C can be used to exit.

Controlling the car directly would be more efficient, but as far as a proof of concept, doing it indirectly through the remote control works really well. Adding the Camera Module would be a good next step, but even at this point the process has got me thinking that a Pi Zero would be a nice addition to a platform like RC car that you can buy at the store — especially something like this Fast Traxx. Driving it with a keyboard over SSH is such a cool experience.


TensorFlow.js Component Playground

A progressive web app with pwgen.

After experimenting with the AIY Vision kit and the Coral USB Accelerator I decided to try “edge computing” from another angle by wrapping up TensorFlow.js with LitElement to make a few Web Components for testing. The tfjs-backend-wasm package is loaded to use WebAssembly for the backend and while it seems similar to WebGL for lite models, it performs worse when using medium-sized ones. Fortunately, they’re commited to supporting the platform and will continue to improve it.

The models are setup with little modification to the configuration, so watching what’s detected and how things are classified before diving into the actual building and changing of them is interesting. Google’s AutoML project might be something to check out next. Each component has methods exposed so the user can provide images or video to inference—for example:

The last thing of note is that all image classification, object, and facial detection is completed client-side. It’s by design, more private by not sending the data to the server—kind of neat.


Compiling pwgen to WebAssembly

A progressive web app with pwgen.

While there are many ways to generate strong passwords, I’ve been a fan of using pwgen for systems that I stand up. It’s usually been an “apt-get install” away, but there have been times while away from a Linux machine where I couldn’t access it like I normally would; right on the cli.

After coming across a Docker image that sets up most of the environment to compile a C/C++ project using Emscripten, it got me thinking that it might be easier than I thought to build a Wasm version of the original pwgen. It progressed something like this, “I can currently use it on the Linux command line—but with WebAssembly on Node.js and Wasmer, I could run it on Mac OS X, Windows, and really anywhere a runtime isI think I can wrap this in a custom element.”

So, I gave it a shot, and I couldn’t be more pleased with how easy the results are to use and in how many environments it runs on. Does the system already have a recent setup of npm/npx installed? Start generating passwords with the command below (wapm is similar), or pass “‐‐help” for additional options to be printed.

npx pwgen

What about from the browser?

The PWA works offline, includes a minimal view for displaying passwords, some sliders to adjust the settings, and the x-pwgen Web Component that wraps up everything. At first I was a bit surprised that the JavaScript wrapper that Emscripten provides to load the module is larger than the Wasm itself, but it still loads fast. To use it in React, Angular or anywhere else HTML likes to hide out, declare the following:

<x-pwgen></x-pwgen>

<script type="module">
  import 'https://unpkg.com/pwgen'
</script>

Finally, I felt like this was a good opportunity to investigate Web Bundles [1 ,2] seeing how the hosted version is a just a set of static files. If you use Chrome 80 or higher and want to test it, set your brower’s chrome://flags/#web-bundles flag to enabled, download the pwgen.wbn file, and then drag and drop it onto a Chrome window.

Checkout the project at Github, or browse some demos [1, 2] to find out more.