This Tiny GameCube Keychain Controller Actually Works

Any electronics enthusiast who sees a mini novelty video game controller keychain has the exact same thought: Can I make this actually work? YouTuber Brux recently picked up a Backpack Buddies GameCube controller and decided to find out. It is very small, leaving little room for adding electronics, but Brux was determined to find a way to make it happen.

Despite the tiny shell, Brux managed to cram in dual analog thumbsticks, working shoulder buttons, a microcontroller, and all of the wiring needed to communicate directly with a Nintendo GameCube or other system via a GameCube-to-USB adapter.

Brux got started by cracking open the controller’s case. Nearly all of the internal plastic supports and fake button mechanisms had to be removed using a rotary tool to free up enough space for real electronics. Once the shell had been hollowed out, custom 3D-printed brackets were designed to hold tiny tactile switches and joystick assemblies in just the right positions.

For the electronics, Brux selected a Waveshare RP2040-Zero microcontroller board. The RP2040 chip was programmed with firmware that allowed the tiny device to function as a native GameCube controller. Due to the severe space limitations, the board had to be wedged somewhat awkwardly between the two joystick mechanisms — but hey, it worked!

Ultra-low-profile surface-mount tactile switches were installed beneath the A, B, X, Y, and D-pad buttons, while miniature switches handled the shoulder triggers and start button. The original plastic keychain buttons were trimmed and modified so they could physically press the new switches underneath.

Standard hookup wire would have been too bulky, so Brux used extremely thin enamel-coated magnet wire to connect every button, joystick axis, power line, and data signal to the RP2040. The resulting internal layout was a dense web of hand-routed connections packed tightly around screw posts and moving parts.

The analog sticks were also turned into real input devices using miniature joystick potentiometers. Custom plastic extensions helped transfer movement from the external thumbsticks to the internal hardware.

Brux demonstrated the controller working flawlessly in Fortnite. The device was also plugged directly into a Nintendo Wii, where it was used for a few laps in Mario Kart. It can’t possibly be a good gaming experience, but it was obvious from the beginning that this would be the case. The important thing is that it does actually work. Now we just need a wireless version so it can still be used as a keychain.