N64 to Gamecube Controller Adapter

In 2009, I wanted to play some N64 games of mine, but all the controllers had worn down control sticks and it made things frustrating. I looked at cleaning or repairing them, but after a few failed attempts, it was clear I needed to try something else. I started looking at making an adapter to play the N64 using a Gamecube controller.

I found the existing Cube64 Project which did exactly that using a PIC microcontroller. At the time, I had 0 experience with programming microcontrollers, and programming a PIC required some programming circuitry that I didn't quite understand. Perhaps it wasn't that complicated, but my brother did happen to have an Arduino laying around, so I decided to take a shot at writing the code for the Arduino.

This is that code. With only an Arduino and a 1K resistor, I successfully enjoyed my N64 games using a Gamecube controller, complete with Rumble!

Materials

This is an extensive list of what's required. A lot I had laying around already, nothing was that expensive.

• A Gamecube controller
• An N64
• An Arduino. I used the Duemilanove with an AtMega328 running at 16MHz. A different chip may have different timings, and a different speed will most certainly require modifications to the timing code.
• Gamecube controller extension cables. I picked a couple of these off eBay so that I didn't have to splice my GC controller cables up. I spliced the extension cables to plug into the arduino, so I would have a nice socket to plug the GC controllers into.
• A 64 controller, to splice the plug from. A 64 extension cable would also work, but since my existing controllers were pretty much useless, I cut the cables to use to connect the Arduino to the N64 itself.
• Some wire and alligator clips or a breadboard or something to hook everything up with
• A single 1K ohm resistor, as a pull-up resistor. Higher resistance will probably work just fine. I'm not an electronics guy, but the 1K works fine for me.

Quick Setup

To just get things up and running, here's what to do:

Hooking the N64 to the Arduino

The N64 controller cord had 3 wires: ground, +3.3V, and data. The pin-out is shown in Figure 1 (left).

1. +3.3V (red) - connect to nothing
2. Data (white) - connect to Arduino digital I/O 8
3. GND (black) - connect to Arduino ground

The wire colors may or may not vary depending on the model, I would check that the wire colors match the pin-out before you connect them up.

Figure 1: Pin numbers for an N64 plug (left) and a Gamecube socket (right). Credit to this diagram goes to the Cube64 project.

Hooking up the Gamecube controller to the Arduino

The GC controller cord had 6 wires: +5V, +3.3V, data, 2x ground, and one unused wire. The pin-out is shown in Figure 1 (right).

1. +5V (green) - connect to Arduino +5V supply
2. Data (red) - connect to Arduino digital I/O 2
3. GND (yellow) - connect to Arduino ground
4. GND (brown) - connect to Arduino ground
5. N/C (black) - don't connect
6. +3.3V (orange) - connect to Arduino +3.3V supply

The internal wire colors may vary from the ones listed here. Remember, I spliced some third party GC cables I got off eBay, so I wouldn't be surprised if the wire colors were not the same as an official GC controller. Verify the colors match the actual pin-out.

Also, as you can see, the Arduino provides power to the controller: 3.3V to the circuits, and 5V for the rumble. The Arduino needs its own power supplied to it, either via USB or an external power brick. The N64 doesn't provide enough power for the Arduino.

Attaching the Pull-up Resistor

The protocol requires the data line to be idle-high, so attach the 1K resistor between digital I/O 2 and the 3.3V supply. This will keep the line at 3.3V unless the Arduino or the controller pulls it down to ground.

Compiling the Code

gamecube.pde provided is the entire source. You can open it with the Arduino IDE and compile it, that should work. I've also provided a Makefile that I used when developing it (since I needed to analyze the pre-assembled code). If you use the makefile, you may need to edit the top for the locations of the Arduino libraries.

Running it

Once the code is loaded on the Arduino, and everything is hooked up, it's ready to use. When the Arduino first powers up, it waits for a signal from the N64. Therefore, the Arduino must be powered on and ready (wait a couple seconds) before the N64 is turned on. Then turn the N64 on and it should be good to go.

If you turn the N64 off to e.g. load a new game, you'll need to reset the Arduino. Just hit the reset button when the N64 is off before you turn it back on.

I've tested this with every game I have, and it works with both wired controllers and the wavebird. I haven't tried it with any third party controllers.

Configuration

There are two things that people may want to customize. Both of them require editing source code, I didn't make any easy or dynamic interface to them.

X and Y button mappings

Since the X and Y buttons don't exist on the N64, one has some freedom in mapping these buttons. I like to map them to C-down and C-left respectively for games like Starfox where those buttons are more significant. For something like Perfect Dark where C-left and C-right strafe, I map X and Y to those instead.

You can go to around line 235 in gamecube.pde to configure the mapping. Try uncommenting the mapping for X -> Cdown and comment out the line for X -> Cright if you'd prefer that mapping.

Analog Stick Curve

On some games, such as Perfect Dark, the control stick feels a bit weird. That is, it feels too sensitive, like there's not enough difference between fully tilted and slightly tilted. (or maybe it was not sensitive enough, I forget)

To help with this, I apply a curve mapping inputs on the GC controller to outputs on the N64 "controller" in a non-linear fashion.

Figure 2: A graph showing a linear mapping of inputs to outputs (red) and a cubic mapping from inputs to outputs (green). Inputs (from the GC controller) are along the X axis, while outputs (to the N64) are on the Y axis.

To turn this off, head to line 279 in gamecube.pde and change the 0 to a 1. In my experience, this curve helps in some games, but hurts in others.

Method

Here's the technical info on how all this works

Hardware Setup

The gamecube connection has 6 wires: 2 ground, a 3.3V rail, a 5V rail for rumble, a data line, and an unused line. The data line goes into digital I/O 2. The rest go in their obvious places.

The N64 has 3 wires: 3.3V power supply, data, and ground. I don't use the power, the arduino needs to be powered externally anyways and provides its own 3.3V supply. The data plugs into digital I/O 8 and ground goes to ground.

Pull-up Resistor

The line to the controller is idle-high at 3.3V and is brought low to signal a bit. This means we can't use the Arduino's built-in pull-up resistors to signal, since they operate at 5V. The solution I found works is to bridge the Arduino's 3.3V supply and digital I/O pin 2 with a 1K ohm resistor. This keeps the line high at 3.3V when the pin is in input mode, and can be lowered by setting the pin to output a 0. Thus forming the signaling mechanism.

Signaling

The protocol is simple, it uses low pulses of either 1μs or 3μs to indicate a 1 bit or 0 bit respectively. Bits come in every 4μs, so a 1 bit is 1μs low followed by 3μs high.

This microsecond timing is no problem for the AtMega328, but it does cut it kind of close. At 16MHz I get exactly 16 clock cycles per microsecond. Which is for the most part plenty, but one code path where the loops iterate on a byte boundary with a 1μs budget takes exactly 16 cycles.

Coding

I coded the entire signaling routine (sending and receiving) in C, and then analyzed the assembly output, calculated the number of cycles each branch took using the AVR Instruction Set manual, and added in the necessary number of "nop" instructions. Then re-compiled and tested.

After some trial and error, I was successfully sending and receiving commands from a gamecube controller. The N64 was easy after that, since they used the same encoding.

Resources

• The Cube64 Project
• Gamecube Controller Protocol information
• Nintendo 64 Controller Protocol information
• N64/Gamecube to USB adapter Project had some code that was useful as a reference
• N64 to GameCube conversion project (not sure why anyone would want to go in this direction)

See Also

Since this project hasn't been updated in a while, check out NicoHood's Nintendo project, and the related HID project for a more polished library for connecting gamecube controllers to the Arduino and to the computer.