Record and play DTM (Dolphin TAS Movie) files on a GameCube. A Raspberry Pi Pico acts as a man-in-the-middle between a controller and a GameCube and passes inputs, and records them to an SD card, from the controller or a DTM file to the GameCube.
┌────────────┐ ┌──────┐ ┌──────────┐
│ Controller │ ◂──▸ │ Pico │ ◂──▸ │ GameCube │
└────────────┘ └──────┘ └──────────┘
- Passthrough: passes inputs from the controller to the GameCube and shows digital buttons on the screen when pressed. Great for checking if all the wires are properly connected. Also shows a blinking square at the bottom left corner, so you know it's running.
- DTM_Playback: reads a file named
REC.DTMfrom the SD card and replays inputs to the GameCube. The display shows how many inputs have been sent to the GameCube as a percentage. - DTM_Recording: passes inputs from the controller to the GameCube and records them to a file named
REC.DTMon the SD card. The file is always overwritten when powering the Pico, so be careful! PressingStart + Z + Ystops recording and finalizes the DTM file,Start + Z + Bpauses the recording andStart + Z + Aresumes recording from a pause state.
Passthrough mode with A button pressed.
DTM_Playback mode with 20% of inputs sent.
DTM_Recording mode with no SD card inserted.
You can check out a video of how DTM_Recording and DTM_Playback modes run here with a Dolphin Emulator run included for comparison. The REC.DTM file for these recordings is included in this repository. The header has been edited, so it can be run on Dolphin (see FAQ below). You'll need the PAL version of Metal Gear Solid: The Twin Snakes to try it out.
- Raspberry Pi Pico. The
PICO_BOARDvariable inCMakeLists.txtis set topico2, but you can change that to whatever board you're using. - GameCube extension cable. Split it in half and solder proper connectors to the wires so you can hook them up to the Pico.
- ST7735 display with an SD card slot. Mine's red with a green tab on the sticker on the screen. I had some trouble identifying what init sequence to use, but the one used by gcbot is supposed to be generic.
- SDHC card formatted as
FAT32. MMC or SDSC will not work. Don't keep important files on this card! - A three-way toggle switch is optional, but makes switching modes a lot faster.
gcbot wired up. The Pico board is a Pimoroni Pico Plus 2 with stacking headers.
gcbot is powered by the GameCube 3V3 line, but you could also use the 5V line connected to VBUS, since controller rumble is disabled.
Label colors below should correspond to wire colors in official controllers.
A three-way toggle switch works best, but you can also just connect a jump wire from GPIO6/7/8 to GND. The GPIO pins have pull-ups enabled. If nothing is connected, gcbot will default to Passthrough mode.
Pico Toggle Switch
┌─────────────────────┐ ┌──────────────────────┐
│ Passthrough GPIO6 │ ──▸ │ pin 1 in pin 1 out │ ──┐
│ DTM_Playback GPIO7 │ ──▸ │ pin 2 in pin 2 out │ ──┤
│ DTM_Recording GPIO8 │ ──▸ │ pin 3 in pin 3 out │ ──┤
│ │ └──────────────────────┘ │
│ GND │ ◂──────────────────────────────┘
└─────────────────────┘
You can measure the execution times of console.WaitForPoll() on GPIO28 and console.SendReport() on GPIO27 with a logic analyzer in Passthrough mode. Remember to hook up the logic analyzer ground to a GND pin on the Pico.
PulseView showing WaitForPoll and SendReport timings and GameCube and controller Joybus traffic.
joybus-pio for Joybus (the controller protocol) I/O.
no-OS-FatFS-SD-SDIO-SPI-RPi-Pico for SD card I/O.
Q: Can gcbot do TAS runs?
A: I doubt it. AFAIK a badly timed seek on the optical drive can cause a run to desync which makes frame perfect inputs impossible. Maybe running games from a solid state drive on a modded GameCube might work better. Same desync problem applies to normal runs as well.
Q: Can I run the REC.DTM file on Dolphin?
A: Yes, but you need to add the Game ID (at 0x04, six bytes), VI count (at 0x0D, eight bytes) and tick count (at 0xED, eight bytes) to the file header. gcbot can't track VI or tick count, so you could multiply the input count (at 0x15, eight bytes) with 60 for VI count and 10M for tick count, I guess.
Q: Can I run DTM files recorded on Dolphin?
A: Yes, just rename the file to REC.DTM before transfering it to your SD card. Remember to run files that are recorded at the same frequency (50 or 60 Hz) that the game runs on! No guarantees on the accuracy.
Q: Something went wrong and my computer doesn't recognize my SD card! Any advice?
A: Use SD Memory Card Formatter (Windows/macOS and Linux) with the --discard switch.
DTM Format (tasvideos.org)
FatFs - Generic FAT Filesystem Module (elm-chan.org)
