A small update: With a RaspberryPi B+ the GPIO Controller works. Only with my RaspberyPi 2 it does not work.
I openened an issue https://github.com/digitalLumberjack/recalbox-os/issues/24
When I assign the Hotkey to the Select button is not a real good solution. When I do that it cloeses the emulations wenn I need to use the select button.
That's a bug since the shortcut to exit games is : Hotkey + Start Could you tell me more about that ?