I have mounted a raspberry PI inside an old rotary dial phone. I put an Adafruit stereo speaker bonnet on the Pi. It provides 3w to two entirely separate circuits for true stereo separation. I replaced the mic and speaker in the handset with a pair of 3w speakers, and run the power through the original base <--> handset cord.
It works great!
I would also like to be able to hook it up to a stereo or headphones with a mini jack, instead of using the handset. I got this rj45-mini adapter, but the pins weren't arranged properly out of the box (because when I rewired the phone, I didn't pay any attention to which pins went where.)
Rather than rewiring the phone and handset again, I want to open up the adapter cable, and cross some wires over to make it work with the rj45 wired the way it is.
I am uncertain, though, if I can do that. Headphones share a ground, but the signals on this unit have two separate grounds. Does that matter?
Should this scheme work?
Bonnet L+ ---> Mini Jack Tip Bonnet R+ ---> Mini Jack ring Bonnet L- ---> Mini Jack sleeve (Shared Ground) Bonnet R- ---> Mini Jack sleeve (Shared Ground)
I have been trying to dummy up the circuit with alligator clips and stripped wires, and I keep causing the Pi to freeze up. I don't know if that is because I am not getting the right pins connected or because it won't work even if they are connected.