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Summary here
USB Command Protocol
Commands are sent over the WebUSB command endpoint. This reference is for developers building web clients or debugging adapter behavior.
Command ranges
| Range | Module | Commands |
|---|---|---|
0x00–0x0F | Control | 0x00 SetMode, 0x01 Cancel |
0x10–0x1F | GBA Link | SetModeMaster, SetModeSlave, StartHandshake, ConnectLink |
0x20–0x2F | GBA Emu | (internal section commands) |
0x30–0x3F | GB Link | 0x30 SetTimingConfig, 0x31 EnterPrinter, 0x32 ExitPrinter |
0x40–0x4F | Hardware | See below |
Hardware commands (0x40–0x4F)
| Command | Name | Description |
|---|---|---|
0x40 | Voltage3V3 | Select 3.3V link level |
0x41 | Voltage5V | Select 5V link level |
0x42 | SetLEDColor | Set LED color live (preview) |
0x43 | RebootBootloader | Enter UF2 bootloader |
0x44 | SetWebUsbLanding | data[1]: 1 = on, 0 = off. Persists whether adapter advertises launcher.gblink.io on connect. Stored in flash. Current state reported as 5th byte in 0x0F GetFirmwareInfo response. |
0x45 | GetLedConfig | Returns persisted per-mode LED colors: [0x45, count, r,g,b …]. Slots: 0 idle, 1 GBA/Celio, 2 GB/GBC, 3 printer, 4 Advance Wars. |
0x46 | SetModeLedColor | [0x46, slot, r, g, b] — persists a mode’s color (applied on next entry) |
0x47 | ResetLedColors | Restores all slots to built-in defaults |
LED colors are full 0–255 RGB. On a WS2812, magnitude also controls brightness.
Control commands
0x00 SetMode
Sets the firmware operating mode. See Supported Modes.
0x01 Cancel
Cancels the current operation and returns to idle.
0x0F GetFirmwareInfo
Returns firmware version and configuration. The 5th byte includes the current WebUSB landing page state.
GBA Link commands (0x10–0x1F)
| Command | Purpose |
|---|---|
| SetModeMaster | Configure connected GBA as link leader |
| SetModeSlave | Configure connected GBA as link follower |
| StartHandshake | Begin link handshake sequence |
| ConnectLink | Establish link connection |
GB Link commands (0x30–0x3F)
| Command | Purpose |
|---|---|
0x30 SetTimingConfig | Adjust GB link timing parameters |
0x31 EnterPrinter | Enter Game Boy Printer emulation mode |
0x32 ExitPrinter | Exit printer emulation mode |
Implementation notes
- Web clients communicate via WebUSB and WebSerial — no kernel drivers required.
- On Linux, install udev rules via
./scripts/setup-permissions.sh. - If the firmware does not respond to a mode-switch command, reboot the device.