To whom may interest: I found the way to make it work. 1.- Using clrmamepro, transformed all my roms to version 0.78 using the .DAT file from the retropie website https://github.com/retropie/retropie-setup/wiki/Managing-ROMs 2.- modified my recalbox.conf and set mame.emulator=libretro and mame.core=mame078   Worked like a charm!

Hello! I am a bit confused, i am trying to make my MAME roms work in Recalbox 4.0 but a i am absolutely unable to do it. This is what i've done so far: 1.- I have a mame 0.78 romset (I thought it was the most compatible one) 2.- I have downloaded a mame bios pack (about 68 zips) and put it inside the roms/mame folder, along with the other roms 3.- I've seen in the wiki that romset 0.78 should be using lr-mame2003 emulator, but i don't know how to specify it in the cfg file, so i let it as "default" (in the cfg i only see "mame.core=mame078") 4.- Tested some roms, and sunset riders, bubble bobble, superman, track and field, and many more are not working. What should I do to make it work? Is there a specific 0.37b5 and mame4all or it should work right away? Thanks!

Entering the virtual gamepad page while i am in the home menu seems to work ok, it was not working because i was trying to activate my virtual gamepads when i was inside a game. Thanks!

Hello, First of all, congratulations for your job with the GREATEST project in the whole internet. I have been able to setup everything ok on Recalbox 4 I have a GPIO controller configured and set the: controllers.gpio.enabled=1 and controllers.gpio.args=map=1 To make the first player use the GPIO controller. The problem comes when I try to connect a virtual gamepad with the mobile phone, to play a two player game (first player using GPIO controller and second player using virtual gamepad), a "virtual gamepad connected" message appears on the screen, but it simply doesn't work. Should I do something special to make the virtual gamepads work along with the GPIO controller? Thanks!