Adding USB controllers to retropie 2-player arcade cabinet

stevepax

I have a working retropie arcade cabinet, built it myself. 2 joysticks, 6 buttons each, using an IPAC2 control board, so both player 1 and player 2 go through a single USB connection into the top left USB jack on my raspberry pi.

This probably isn't important, but each player also has a start and coin/select button, and there are dedicated buttons for pause and exit. (I have the hotkey set to "nul" in my config file, so I can have dedicated buttons for those. For other special functions, I just use the IPAC2 "shift" feature.)

I want to be able to occasionally add a couple of regular hand-held USB controllers (maybe x-box style or whatever) to play 4 player games like TMNT and The Simpsons or whatever. If I simply plug those controllers into, say, the right two jacks on my raspberry pi, what will happen?

Will I be able to configure them at that point, as players 3 and 4?
If I then disconnect them for a while and then plug them back in next time I want to play TMNT again, will retropie recognize them and use the configuration I did before?
Will plugging them in only occasionally and disconnecting, etc, do anything to all the configuration I did on my ipac2? Like, when I take the USB controllers out, will my joysticks and buttons still work as player 1 and 2 as they do now, without getting messed up?

I'm terrified to mess up my configuration, as the MAME stuff took me way too long to figure out how to get the buttons working the way I wanted!

Thanks in advance for any help.
-Steve

Clyde

@stevepax Hello and belated welcome to this forum. I'm close to finishing my own arcade cabinet myself and I plan to do something similar to you but with two bluetooth controllers for players 3 + 4. I didn't dive into the matter deeply yet, however, but I'll try to answer your questions to the best of my current knowledge.

If the emulator and the game rom support four players, you should be able to configure the controls for players 3+4 just like those for players 1+2. Mind that some games come in different versions (roms). TMNT has 2 and 4 players versions, for example. Its 2 players versions have "2p" in their rom names.
At least Retroarch should recognize your controllers upon reconnection. A common advice is to connect them every time to the same usb ports in the same order. There's also a script by @meleu called joystick-selection that simplifies the mapping of controllers to players, and if the controllers should be recognized by their names or by the ports they're plugged into.
Alas, I don't know.

You're rightly terrified to lose your configuration if you didn't backup it recently. Do so now, because bad things happen all the time to "valuable" data, e.g. storage failure. (I put "valuable" in quotes because there is a saying that data with no backups isn't important by definition; if it were, it would have backups.)