@PetroRie

Thanks - I do have a PS4 so will give that a go later. Cant get much cheaper than "already have"!

From the RetroPie-Setup I uninstalled unnecessary components -- remove WolfRam, SonicPi, etc. Nothing more than a boot to emulator, so I figured I would get some clutter out of the way.

I then went back to trying to different gamepad configurations through the driver config file. I enabled all four ports and through sheer dumb luck GPIO7 (gamepad4) started reading. I still cannot get GPIO2 / GPIO3 to read the data from the controller, but I have two working NES controllers right now!

I also tweaked the /opt/retroarch/configs/all/retroarch.cfg

There is a setting for joypad input scan cycle -- something along those lines -- that I opted to put at a value of 0 (I am trying to recall this from memory as the NES is now wrapped under the tree for dad) so that it would update controller state on demand. It was defaulted to 2 and the notes in the file were about adjustments for latency issues.

I also had to copy the configuration for player1_input* and update it for player2 within /opt/retroarch/configs/all/retroarch.cfg.

Also removed the override line from /opt/retroarch/configs/nes/retroarch.cfg

Still no idea why I cannot access GPIO3 / GPIO2 -- if anyone has any troubleshooting ideas I would be happy to jump through the hoops. I have the other SD card and another Pi3 at home I can run through.

Alright quick update.

I went back through the SNESDev github page. https://github.com/petrockblog/SNESDev-RPi#snesdev-rpi

I was able to get my first controller to be recognized and it seems to be working correctly but I had to use putty to ssh in and run sudo SNESDev. If I close putty it stops working.

On the github page it says to run:
sudo ~/SNESDev-RPi/bin/SNESDev &

This fails. I am am not sure what is going on.

I also tried to run:
Running SNESDev as a service

SNESDev-RPi comes with a script that allows SNESDev to be run as a service. The installation command for that is

sudo make installservice

and that fails. I think I am close but I am still missing something here. Can someone who has set this up chime in?

@sixfootewok It'll be seeing the Xbox pad as player 0 (so player 1). Disconnect it and try again, or look into the retroarch controller select script from the wiki so you can define which device is used as the first player.