Retropie with 2 GPIO Controllers - Only one working - 1/2 Not Configured


I bought a Pandora Box and was playing with it for a while, but didn't like that I couldn't add games myself.  So I replaced the Pandora board with a Raspberry Pi 4.

I wired up the joysticks using the GPIO pinout from

The Pandora uses a 40 pin connector, so I purchased a 40 pin breakout cable to rewrite the 40 pin to the GPIO on the Pi.

After wiring up the GPIO, I made a modprobe.d config to load the driver with 2 controllers.

options mk_arcade_joystick_rpi map=1,2

The Problem

Emulation station then recognised my controllers, and I was able to configure each within Emulation station, but when I started a game, libretro would pop this message up:

GPIO 0 Configured
GPIO 1 (1/2) Not Configured

After messing around for a while, I found that I needed to configure the controller within retroarch.

I had to go to Settings → Input → Port 2 Controls

Now when i start games, I see that both GPIO controllers are configured and working.

The GPIO connected: