I still don't know how to do it. I have tried but it doesn't work

@iandaemon yes, that’s pretty much it. Emulation station writes a configure file for retro arch and other emulators. If you change a button in retro arch, say you like to use y and b as your a and b in Nes per say, and reconfigure, it doesn’t effect the hot keys. Those are still mapped to the original emulation station setup. So let’s say you move start to say, R1 in retro arch, start for the hot key will still be the original start you chose in emulation station.

@mitu OK I figured it out. Fist i got into Stargate on RetroPie and re-assigned the game controls to different keys using Tab. "Input, this game". F is fire, T is thrust, H is hyperspace, 1 is player1 start, 2 is player2 start, S is smart bomb, I is inviso, R is reverse, arrow up is UP, arrow down is DOWN. This makes my head easier to remember. Then I went back into EmStation, disconnected the USB gamepad and reconfigured the keyboard as main controller. I set key 1 as Start and key 2 as Select. I also set key T as B and key F as A. Down at the bottom of the configure menu I left hotkey blank and when asked, I selected Yes. I also went into RetroArch/Settings/Input/Hotkey Binds and made sure Press Quit Twice is set to OFF. So to exit the game now I press 1 and 2 together and it brings me back to EmStation. And when the Pi is in the cabinet (hooked up to iPac2), I can work through the EmStation using the Stargate control buttons and never need a keyboard or gamepad again.

Everything worked flawlessly, I really appreciate the event lookup code, I never would have figured that out. I did notice that if a hotkey was enabled that it does not work which I believe you mentioned in the other thread. All in all it does exactly what I wanted it to do.

@mitu Thanks for all your help and effort. I fixed it by checking a bunch of retroarch.cfg's. The one in 'configs/arcade' was at fault.

Makes sense, as I only use the arcade folder on my cab.

@jgraves Thank you very much for the brilliant idea with the diode!!!
This method suited me perfectly :)
But it is not a fact that it will suit others. Because in this case the "hot key" will be unavailable for other functions. (I do not use it).

TriggerHappy kicks a$$ .. thanks for pointing it out

I started to think maybe I'd accidentally changed some obscure Retroarch setting without realizing what effect it was going to have.

So I decided to go back to square one. I reinstalled my disk image and started over. This time when I went in and edited /op/retropie/configs/mame-mame4all/retroarch.cfg it had the desired effect.

The only weird thing I ran into was that key b was set to "reset input" in retroarch when you used the hotkey. With hotkeys disabled that meant I couldn't press my b button. I could remap that input in the games, but I decided to just set "reset input" to nul.

I'm not sure what reset input does, but if I need it I can assign it another key.

@guitarans when it asks for hotkey unless your controller doest have a key you can assign to select, you really should use select as your hotkey. That is how it was originally designed. The only reason they added the hotkey option in the controller config menu in emulationstation was because of people using controllers like the n64 controller or dreamcast controller where they dont have a button to assign to select. It used to automatically assign it to select.