Cannot get controller to do anything on my EmulationStation after game has started

Question

I bought a 6 button controller to use with my RetroPi setup, and it is recognised and configured easily. At least it seems so.

Unfortunately, once I start up a game (say Sonic) no button does anything. I try hitting every button, but no response at all. The only thing that does anything is using my keyboard to enter the meny or quit the game.

Once I am back in the meny of Emulation Station the controller works again. Up/down/Left/Right/A/Start/Select: it all works. But not in the game.

Clues on how to start debugging wtf is going on?

Answer 1

It turned out that my keyboard was picked up as player 1. Thus all the player 2 activity did nothing in the 1 player Sonic Game. Unplugging the keyboard and restarting did the trick.

Now, how to figure out how I can keep the keyboard connected in addition to the gamepad ...