I came across an old broken Yamaha keyboard in my basement why cleaning one day. I decided instead of throwing it out, I will turn it into a midi keyboard. The whole process went very smoothly and although it does not work right now due to recent events it no longer works, I has worked in the past and I plan on fixing it up again.
The keyboard wasn’t too hard to set up, just used a voltmeter to find out the matrix the keys were arranged in then processed them using a Teensy, an Arduino based micro controller. Once processed I can make the controller output a midi signal.
Teensy 3.2, the brain: