GameCube Keychain Becomes Working RP2040 Controller

In the retro gaming scene, mini builds always get attention, and this one is a proper bit of work. Modder Brux has turned a GameCube keychain into a fully functional controller, using a Raspberry Pi RP2040 microcontroller, as first spotted by Hackster.io.

For readers in London and across the UK who follow hardware mods, the appeal is simple, it is not just a display piece. Brux has made a tiny accessory into a usable input device, with the project highlighted by XDA Developers.

To make room for the electronics, Brux used a rotary motor to clear out the keychain’s interior. Custom 3D-printed parts were then fitted inside the shell to support the buttons and wiring, according to Brux on YouTube. Surface-mount tactile switches were used for the button inputs, keeping the build as compact as possible.

The RP2040 does the heavy lifting. The dual-core ARM Cortex-M0+ chip, which runs at up to 133 MHz, handles the input processing and sends the signals through a single cable to a console. That setup is what makes the keychain controller actually work, rather than just look the part.

Brux showed the controller being used with games including Fortnite and Mario Kart. It is not the sort of thing you would take into a competitive Super Smash Bros. Melee match, but it does show how far compact controller builds can go when the electronics are carefully planned.

Brux also teased other keychain ideas, including working N64, SNES and even 3DS controllers. For more retro hardware stories, you can keep an eye on our news tag, or follow the original project coverage from XDA Developers and Hackster.io.