Setting up an N64 controller - kpa32/retropie-wiki-cn GitHub Wiki
From here:
i recently started messing with it again, and used an n64 controller instead. not only does it have more buttons, it also has less to connect, just + at pin 1 gnd at 6, and data at pin 7. as long as you put in
gamecon_gpio_rpi map=0,0,6,0
in
/etc/modules
it starts right up on boot. you also need to run
cd ~/RetroPie/emulators/RetroArch/tools
./retroarch-joyconfig
and save the output to your retropie config file (this is a lot easier if you do it by ssh, with copy paste into vi/nano) to
~/RetroPie/configs/all/retroarch.cfg