It’s been a few months, and many hours of soldering and fixing and test and rinse and repeat.
The rotary encoders were promising, but they introduced some clicking/ticking noises in the analog signals that were not tolerable.
I redid the whole setup to use a Teensy LC and an ESP8266, with the Teensy watching the analog stuff, and sending data over serial to the ESP, which pushes the data to the Raspberry Pi wirelessly.
As the dust settles, I have some good software to share:
This guitar project of mine now uses analog sensors (potentiometers and switches) connected to a Teensy LC, and the ResponsiveAnalogRead / Bounce2 library to read the state of the analog stuff on the face of the guitar.
The Teensy LC pushes it’s info over serial to the ESP8266, which transmits the data via wireless to the raspberry pi with the other software on it.
The Pi transforms the string data from the Teensy/ESP into midi data that is available to other software running on the Pi (MODEP).
Some small adjustments to that base code could easily be tweaked to suit a variety of analog-stuff-to-midi needs.
I am currently planning on taking the core of the code/new parts and making a new foot switch, with some buttons and a 7 or 14 segment display on, it for extra midi scrolling/controls and some feedback, which would be connected via wires (USB probably) right to the Pi.