@THRobinson ahhahaha, I also got new parts for mine, and are also in a box :D

Software is ready to run my own game controller with dynamic lighting based on the emulator running at the time.
Hardware is being built (waiting for some extra components).

Created a project website for it :-p
Retropie stuff

Hardware schematics, software, photo's and video's will be posted ASAP.

Greetings,

ErX

Use python and it's native GPIO support :)
But thank you for the link... So Arduino programs can be ported to RPi.
You can usually use programms in the background to control switches even with ES running - because these programs are not "active" like in windows. They just wait for a trigger to act (=set interrupt)