A small project I did for fun at the start of the lock downs.
It is a 3x3 macro pad with a RGB LED that I hand wired with a Proton-C controller (ARM STM32F303). I programmed it to have 4 layers, and the LED changes color depending on what layer its on.
QMK is an opensource C based framework that lets you program micro controllers. https://docs.qmk.fm/#/
