This software allows for the playback of Mario Kart Wii time trial ghost data on console using a Raspberry Pi Pico and an exposed Gamecube cable dataline connected to a Wii. It's consistently reliable thanks to framecount determinism by starting a time trial race with the controller unplugged because the race pauses on the same frame each time. Plug in the microcontroller with this software and it will close the unpause the game and thereby synchronize frame timings for the race. This project is forked from pico-rectangle as data encoding and transmission timings are already handled. Note that not all ghost data will play back currently (see the Input Range section).
Please consult the Legal information and license section in the upstream repository before using this firmware.
In order to achieve playback sync, I had the following:
- Raspberry Pi Pico
- 2x 20-pin headers
- Breadboard kit
- Soldering iron + solder
- Gamecube cable
- 28 gauge wire stripper
- 2.54mm Dupont connector kit
- SN-28B Crimper
I bought stuff before I had an actual game plan, so I didn't consider that the Pico didn't come with header pins already. You can find these pre-soldered online for near the same price, if you don't have your own soldering kit. If you DO have your own soldering kit, then you can probably skip purchasing the breadboard kit, the Dupont connectors, and the crimper. For the Gamecube cables, you could also just sacrifice an old controller.
- Solder the Pico to header pins. Unlike other Raspberry Pis, the Pico does not come with headers pre-soldered. Connect Pico headers to breadboard kit.
- Cut off the end of the Gamecube cable that does NOT plug into the console. Strip the housing off with something like an exacto knife.
- Locate the data wire. On OEM cables this is the red one, but if using a third-party controller, you should determine the cable by opening the housing on both ends and comparing with a diagram of the pins in the controller port.
- Crimp the data wire to a Dupont connector. Plug the data wire into the GP28 pin on the breadboard kit.
- (Optional) Locate the 3.3V wire. Crimp that as well and plug into VSYS. Alternatively, you can skip this step if you plan to power the Pico via USB. NOTE: If you do this step, do NOT have this board plugged via USB and via its Gamecube port at the same time. This would feed the USB 5v to the 3v line of the console and likely damage it.
For easiest install, I suggest using a Unix environment since that's what I used. Specifically, I just used Ubuntu running through wsl.
sudo apt-get install build-essential gcc-arm-none-eabi cmake -y
- Clone repo.
- In src/file.S, replace file path with a RKG file of your choosing. Be sure to verify that its input set does not contain any tuples outside the valid in-game controller input range.
- Starting from the root directory, run the following:
mkdir buildcd buildcmake ..make
- With the Pico USB disconnected, hold down the BOOTSEL button on-board the Pico, and plug the Pico into your computer.
- Copy the .uf2 over to the Pico which should appear as a new drive.
- Disconnect the Pico from your computer.
- Using a real Gamecube controller, choose the character, vehicle, transmission, and course that matches the RKG file provided, and start a time trial. Immediately disconnect the controller.
- Wait until you see the "Controller disconnected" pop-up screen. Wait a few seconds.
- Plug the Pico's Gamecube wire into the console. If you skipped step 5, plug the Pico back into your computer for power.
- The Pico will now close the disconnect screen and play the inputs from the provided RKG.
The Wii Wheel, WiiMote+Nunchuk, and Gamecube and Classic Controllers have different ranges of possible stick inputs due to code in Mario Kart Wii which clamps inputs to a unit circle (or doesn't, in the case of Wii Wheel). Modern Tool-Assisted Speedruns take use of a Gecko code, which removes the clamp when emulating the game. Since RKG files store inputs the same regardless of the controller used, the in-game replay system will still sync without the use of the unclamp Gecko code. Since I am trying to play back a TAS live rather than through the replay system, this means that the clamp restricts what inputs will work on the Gamecube controller.
Horizontal and vertical stick inputs are each represented in-game as a value between 0 and 14, where 0 represents full left/down, 7 represents neutral, and 14 represents full right/up. The list of illegal inputs, in the format {Horizontal, Vertical}, for a Gamecube controller are as follows:
| {0,0} | {1,0} | {2,0} | {12,0} | {13,0} | {14,0} |
| {0,1} | {1,1} | {13,1} | {14,1} | ||
| {0,2} | {14,2} | ||||
| {0,12} | {14,12} | ||||
| {0,13} | {1,13} | {13,13} | {14,13} | ||
| {0,14} | {1,14} | {2,14} | {12,14} | {13,14} | {14,14} |