Hint: Using 13 Buttons on GPIO

[Lolonois]

Hi guys and gals

For those who are in need to drive 13 buttons (4 directions, 9 function buttons) via GPIO and using up to two joy panels in their build without having to use a GPIO extender like MCP23017.

1. Log in to your RPi

2. Edit file with sudo nano ~/RetroPie-Setup/scriptmodules/supplementary/mkarcadejoystick.sh

3. Make these changes, note the ### and following line. (the version number may vary)

   function _version_mkarcadejoystick() {
   ###    echo "0.1.7"
       echo "0.1.7-hotkey"
   }
   
   function depends_mkarcadejoystick() {
       depends_gamecondriver
   }
   
   function sources_mkarcadejoystick() {
   ###    gitPullOrClone "$md_inst" https://github.com/cmitu/mk_arcade_joystick_rpi retropie
       gitPullOrClone "$md_inst" https://github.com/cmitu/mk_arcade_joystick_rpi retropie-hotkeybtn
       cp /home/pi/git/mk_arcade_joystick_rpi/*.c "$md_inst"
       pushd "$md_inst"
       sed -i "s/\$MKVERSION/$(_version_mkarcadejoystick)/" "$md_inst/dkms.conf"
       popd
   }
   
   

   This will use the branch retropie-hotkeybtn which uses 2x13 GPIO pins but is limited to two GPIO connected controllers.

4. Remove possible leftovers from retropie branch which may make the script fail: sudo rm -rf /opt/retropie/supplementary/mkarcadejoystick

Then run sudo ~/RetroPie-Setup/retropie_packages.sh mkarcadejoystick. Upon a successful build everything should be good to go (I am assuming proper wiring ;-) ). See also testing hints here

NB: If you need more buttons (up to 16 per controller) and/or joystick panels you should stay on the retropie-branch and consider using one or more MCP23017 -- see [1] for details.

Branches retropie-hotkeybtn and retropie confirmed to be working on RPI3 and RPI4.
Should also work on RPI1, 2 and Zero. If anyone can report back on these devices, it will be greatly appreciated.

Cheers

[1] https://github.com/cmitu/mk_arcade_joystick_rpi#more-joysticks-case--mcp23017