The goal of this project is to create a low-cost, easily buildable USB adapter for Gamecube input peripherals.
I own a Wii dance mat and want to play StepMania on it.
Existing commercial solutions tend to be expensive, and cheaper clones are known to have issues. Previously published DIY projects use overpowered (and thus expensive) microcontrollers, are hard to build for inexperienced people and/or do not implement rumble.
Basically, the goal is to make something that can be built by anyone that knows how to use a soldering iron.
I decided to choose the Digispark Attiny85 development board as the base of this project. Clones of it are affordable and very easy to source. The integrated USB plug or port simplifies wiring, and using it as an USB device with V-USB is well-documented. Since it is a development board, no ISP is required to program it.
Gamecube controllers expect both a 5V and a 3.3V supply and operate on 3.3V logic level. To cut down on the amount of external components, a breakout board for the AMS1117 LDO is used to supply 3.3V. The bidirectional level shifting will be done using a traditional circuit based around the 2N7000 MOSFET, which is hopefully able to switch at the required 1 MHz.
Instead of emulating a USB PID (physical interface device) for rumble support, which other developers seem to have no luck with, the Microsoft XInput protocol will be used. Plain USB HID support may be added in the future, either switchable (if memory limitations allow it) or as alternative firmware.
The following estimation is based on the lowest AliExpress prices, including shipping to Europe, at time of writing. Some components are primarily available in bulk, and the PCS column shows the bulk size.
| Count | Component | Est. Cost | PCS |
|---|---|---|---|
| 1 | Digispark (clone) | $1.30 | 1 |
| 1 | AMS1117 breakout board | $1.20 | 5 |
| 1 | GC extension cable | $2.00 | 1 |
| 1 | Perfboard | $1.00 | 5 |
| 1 | 2N7000 MOSFET (generic) | $0.80 | 20 |
| 2 | 10K resistors | $0.70 | 100 |
| Sum | $7.00 |
The extension cable is only required for the female connector. If one is willing to cut off the cable of their controller and hardwire it into the adapter, it can be omitted. Shoving solid wire (e.g. Dupont connectors) in the male GC connector may also work as a short-term solution.
The communication between a Gamecube and its peripherals happens over a proprietary asynchronous half-duplex serial protocol called "Joybus". The data line is pulled up internally by the peripheral, pulled down to transfer a bit, then released again. Stop bits indicate the end of a transmission.
The timings are as following:
- Zero: 3 μs low, 1 μs high
- One: 1 μs low, 3 μs high
- Console stop: 1 μs low, 2 μs high
- Peripheral stop: 2 μs low, 2 μs high
This results in an effective bitrate of 250 kHz at a clock speed of 1 MHz.
The protocol uses a simple request-response model where the console sends a command and the peripheral answers after reading a stop bit.
The stop bits are commonly misinterpreted as ones, and implementing them as such may work in practice. However, the console should release the line quickly after a console stop so the peripheral can answer.
Pin location is given with the flat side pointing up, looking into the connector.
| Female | Left | Middle | Right |
|---|---|---|---|
| Top | (1) 5V | (2) DATA | (3) GND |
| Bottom | (4) GND | (5) NC | (6) 3V3 |
And for quick reference,
| Male | Left | Middle | Right |
|---|---|---|---|
| Top | (3) GND | (2) DATA | (1) 5V |
| Bottom | (6) 3V3 | (5) NC | (4) GND |
- Shinewave, a Gamecube controller USB mod based on the ATtiny84, without rumble
- Gamecube/N64 controller to USB adapter, based on the ATmega32U2
- Earlier revision using the ATmega8/168
- Adapt-FFB-Joy, an AVR-based USB adapter for the Microsoft SideWinder Force Feedback Pro controller
- DigisparkJoystick, HID joystick emulation specifically for the Digispark
- ArduinoXInput_AVR, XInput emulation for AVRs