I didn't have a KB2040 handy that was used in this guide: https://learn.adafruit.com/fisher-price-usb-controller?view=all so decided to take a different approach. Daemonbite Arcade Encoder customized for use with the Fisher Price Controller using an Arduino Pro Micro in DirectInput mode. Works great with the MiSTer FPGA. Source: https://github.com/MickGyver/DaemonBite-Arcade-Encoder/
- X - B1
- Circle - B2
- Square - B3
- Triangle - B4
- Blue Push Knob - B5
- LEFT - speaker off
- MIDDLE - learn mode
- RIGHT - play mode
This alternate method requires less cuts and wires but removes the switch's ability to choose sound "modes." Red wire connection for permanant "play" sounds or omitted for permanent "learn" sounds. I personally prefer the former.