Update:
I have disconnected everything and followed the instructions mentioned here that show how to send MIDI to the UART ports on the Pi. I ran ttymidi -s /dev/ttyAMA0 -b 38400 -p and was able to see output but that was basically 0 or e0 when I didn’t push buttons on my MIDI keyboard and then quite a variety of data as I ran my fingers down every key pretty quickly. I tested this several times over the course of a minute. To be clear: this is
ttymidi <–> RPi GPIO <–> HifiBerry Hat <–> Wires from UART pins on Pi <–> MIDI Connector <–> MIDI Cable <–> MIDI Keyboard.
My keyboard can successfully send data through the hat. Then, when I connect the PCB 2-in-1, I do not get data. I’ve tried several wiring configurations, each assuming the RPi pin 1 is in a different place, I’ve tried inverting the diagram… all kinds of stuff. I guess maybe I have a dud 2-in-1?
MIDI input is obviously a critical feature, so I’m stumped as to what to try next.