Challenges with the firmware: Mostly just learning embedded rust. It's a bit different from regular rust because your don't have access to std (which means no Vec!).

I remember having the hardest time just organizing the code. As in, I wanted to divide everything up into logical segments like, "LEDs", "multiplexers", "infrared", etc and rust makes it kinda hard to do that without making everything it's own little crate. Specifically, if you want your code to be device-agnostic. If you only care about your one board then it's easy and doesn't matter so much 🤷

I got the boards made at JLCPCB because they're the cheapest and seemed good enough 🤷