gba-pico-gamepad

Proof-of-concept Game Boy Advance (GBA) to USB controller, which uses Raspberry Pi Pico as a bridge.

How it's done

This project is essentially a modified version of GP2040-CE that enables communication with the Game Boy Advance using the GBA link cable.

In the original GP2040-CE, key presses were received using pull-up GPIO signals.
However, The GBA link cable only provides 4 pins for the communication, which is insufficient for the 10 keys on the GBA.
To overcome this limitation, GP2040-CE was modified to utilize SPI for receiving packets from the GBA.

To send key presses on the GBA via SPI, an example program from the gba-link-connection was used with a minor modification.

To run this program on the GBA, gba_03_multiboot is ported to the RPi Pico.
This allows for sending a program from RPi Pico to GBA via SPI and running it, eliminating the need for additional hardware such as a flash cart.

And that's about it.

Read this in Korean(한국어) with a little more detail

Usage

1. Download the gba-pico-gamepad-v*.uf2 binary from the Release, and flash it to your RPi Pico.

   • You may have to nuke your RPi Pico before flashing it.

2. Cut your GBA link cable, and wire it to the RPi Pico as below.

   • RPi Pico 21 (SPI0 RX) pin <-> GBA SO pin
   • RPi Pico 23 (GND) pin <-> GBA GND pin
   • RPi Pico 24 (SPI0 SCK) pin <-> GBA SC pin
   • RPi Pico 25 (SPI0 TX) pin <-> GBA SI pin
   • 
   • Raspberry Pi Pico Pinout
   • GBA Link cable Pinout
     • Your GBA Link cable colors are likely to be different.
       It is highly recommended to cut and open the shell to see your pinout.
     • 

3. Connect this cable to the GBA and turn it on without a cartridge.

   • The program is sent from RPi Pico to GBA via multiboot, and with a cartridge it will not work.

4. Plug the USB Cable to your PC.
   It will start sending the program once the GBA is ready.

   • You can hold down certain key on boot to change Input Mode.
     • Note that the key binding is differ from the original.
     • Hold B on boot -> Nintendo Switch
     • Hold A on boot -> XInput
     • Hold L on boot -> DirectInput/PS3
     • Hold R on boot -> PS4
   • You can change the D-Pad Mode anytime with certain key combination.
   • GP2040-CE's Web Config is disabled.

5. Enjoy your GBA as an USB gamepad.

   • If you accidentally pulled out your cable, you can re-plug it and press Start to reconnect.

Build

This is a build process for the Ubuntu 22.04.
You have to use WSL2 if you are on Windows.

1. Install devkitARM and gba-dev package.

2. Install the dependencies via command below.

   sudo apt install -y cmake xxd python3

3. Run this command to build.

   Change the path if you have installed devkitARM somewhere else.

   export DEVKITPRO=/opt/devkitpro/
   export DEVKITARM=/opt/devkitpro/devkitARM/
   export PATH=$DEVKITARM/bin:/$DEVKITPRO/tools/bin/:$PATH
   export CC=$DEVKITARM/bin/arm-none-eabi-gcc
   export CXX=$DEVKITARM/bin/arm-none-eabi-g++
   
   ./build.sh

4. If everything goes right, you should see the build/gba-pico-gamepad.uf2 binary.

Credits

This project is essentially an integration of the projects listed below.
Without them, this would not have been possible.

• gba-link-connection : Game Boy Advance (GBA) C++ libraries to interact with the Serial Port.
• GP2040-CE : Gamepad firmware for the Raspberry Pi Pico
• gba_03_multiboot : Raspberry Pi GBA Loader
  • It's integrated in GP2040-CE/src/gba/multiboot.cpp

License

See the license of each project above.
/build.sh is 0BSD.