So for fun, I have been playing around with NintendoSpy and an Arduino Uno, trying to get Gamecube inputs to display on my computer, following https://github.com/jaburns/NintendoSpy/blob/master/docs/tutorial-gamecube.md. However, no matter what I try, NintendoSpy will not pick up my inputs, and furthermore, whenever I connect the ground wire to the GND pin on my Arduino, the Gamecube stops receiving inputs completely, and will not respond until I unplug the ground wire from GND. I am 95% my wires are correct, as it has pinouts for the extension cables in the guide, and the one I use is listed. Also, the Arduino Serial monitor shows nothing, although I do not know if that means anything. If anybody has any experience with this sort of thing, please let me know. Any help is appreciated.

I don’t have any experience in making input displays, so I can’t provide much help there.

However, I wanted to say that would recommend using RetroSpy instead as zoggins maintains that a lot whereas NintendoSpy hasn’t been updated in 5 years https://github.com/zoggins/RetroSpy

I don’t know if NintendoSpy is just old and not working for you or if it’s an actual hardware implementation problem, but I wanted to toss that out there just in case.

I use Nintendospy and an Arduino Uno for my input display, albeit for SNES.

I can probably help you more directly with more information.

I'd need to see: -Your wiring, both into the arduino and where you have it spliced into your lines, and -The code you're using

Im on Discord most hours of the day and work at a desk, feel free to add me there if you want more immediate/direct help.