Confused mapping ipac buttons to retroarch for mame

[mlcampbe]

I understand the ipac and have used it for many years on my PC with my control panel. It is a simple layout that consists of the following to play the 80's classic games:

coin
1 player
2 player
joystick (up, down, left, right)
4 pushbuttons
pause
exit

My confusion comes in how to map the 4 pushbuttons to the correct retroarch values. For example, I see a lot of configs that use the following:

input_player1_a = "ctrl"
input_player1_b = "alt"
input_player1_y = "space"
input_player1_x = "shift"

I have programmed my ipac so that my 4 pushbuttons send ctrl for 1SW1, alt for 1SW2, etc... That part is good and has been in use for years on my existing PC cabinet.

But how do I know which of the retroarch a, b, x, y buttons are used by the mame games.

For example, take donkey kong which uses a single jump button. In my case I want to use the ipac 1SW1. In my current setup 1SW1 is programmed to send "ctrl" and it works. But how do I know if "ctrl" should be tied to a, b, x, y, l, or r?

In other words, using the above mapping, if I press the 1SW1 button on the panel it will generate the "ctrl" key and send it to the pi. Retroarch will receive the "ctrl" and look to see that this maps to the "a" input and send it to donkey kong. However, how do we know that the "a" input causes Mario to jump?

Is there a standard retroarch <--> mame key mapping that says retroarch "a" = mame "1SW1" and so forth?

[dankcushions]

@mlcampbe said in Confused mapping ipac buttons to retroarch for mame:

Is there a standard retroarch <--> mame key mapping that says retroarch "a" = mame "1SW1" and so forth?

1SW1 is an ipac designation, but afaik it effectively means "mame, player 1, button 1". with that in mind, you can see what retropad button = what mame button number via observing what is displayed in the core input remapping menu: https://retropie.org.uk/docs/RetroArch-Configuration/#core-input-remapping (where you can also adjust the mapping).

please fill out https://retropie.org.uk/forum/topic/3/read-this-first for more specific advice - not all mame cores have the input descriptors required for core input remapping.