osnoogie,
Will that wiring setup, and using the GPIO be compatible with all other emulators (NES, SNES, Sega, ATARI, etc)?

I’m pretty new to the whole Lixux/Debian based programming and have completed building a full, 2-player arcade cabinet based on Lusids Arcade Flashback design. I’ve been fighting like mad to get it to work with an iPac2 controller (which RetroArch will not recognize at all for programming keys) and am seriously looking at wiring it directly into the GPIO.

Current Setup:
RetropPie 3.0 Beta V2