There are 2 repositories under gamecube-controller topic.
Joybus protocol (Gamecube controller) implementation for the Raspberry Pi Pico (ARM Cortex M0+). Translates GPIO to modelized Gamecube controller states based on the B0XX/F1 layout.
A Wii/Gamecube homebrew to test your Gamecube controllers
iOS GameCube controller for the Dolphin emulator.
Work in progress! Read and write gamecube controller protocol. For Teensy 3.6 / 3.2
Allows Nintendo-compatible GameCube USB adapters to emulate Xbox 360 controllers.
GameCube controller analyzer for Saleae's Logic software
Twitch Plays Stuff
An input plugin for Mupen64Plus which lets you use your Wii U/Switch GameCube controller adapter
(HAX-like UCF) Gamecube Controller External Arduino Adapter Cable
Hardware files for a custom Gamecube controller that uses Hall effect magnetic sensors to read the sticks. Based on PhobGCC.
Modify a SNES (or similar) controller to work on GameCube using a compatible Arduino board.
A modded Gamecube controllers, to have all the original button colours, but in a LED form instead
A GameCube controller library to work with ESP8266
Library for reading Nintendo game controllers on Arduino boards, targetting STM32F1/Maple Mini.
A Nintendo Gamecube controller adapter for MSX
wii-u-gc-adapter packaged for the Steam Deck
A simple gamecube controller protocol implementation for the Basys3 FPGA board
A Go library for interfacing with the Gamecube controller adapter.
Use Gamecube joysticks with your MSX computer
Arduino code for the Donkey Kong bongos and the most accurate documentation on Gamecube controllers
A simple module to handle a gamecube controller on a FPGA.
DKMS Driver package for overclocking the Nintendo Wii U/Mayflash GameCube adapter on Fedora, RHEL, OpenSUSE, and OpenMandriva.
Interfaces to game console controllers and joysticks on the PIC32
Convert Dolphin's DTM inputs into actual Joybus responses
PCB for a gamecube to N64 controller adapter