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Output Interfaces

An output interface translates the common input_event_t format into a console-specific or USB protocol. Output drivers read from the router and send data to the connected console or host device.

Console outputs use RP2040 PIO state machines for cycle-accurate protocol timing. They run on Core 1, isolated from USB and Bluetooth processing on Core 0. USB and UART outputs run on Core 0 since they are not timing-critical.

All Output Interfaces

Output Protocol Location Max Players PIO Programs Notes
GameCube / Wii Joybus src/native/device/gamecube/ 4 joybus.pio Requires 130MHz overclock. Rumble feedback. Keyboard mode.
PCEngine / TurboGrafx-16 Multiplexed src/native/device/pcengine/ 5 plex.pio, clock.pio, select.pio Multitap emulation. 2/3/6-button and mouse modes.
Dreamcast Maple bus src/native/device/dreamcast/ 4 maple.pio Rumble feedback. Analog triggers.
Nuon Polyface src/native/device/nuon/ 8 polyface_read.pio, polyface_send.pio Tempest 3000 spinner support. In-game reset (IGR).
3DO Parallel bus (PBUS) src/native/device/3do/ 8 sampling.pio, output.pio Mouse support. Extension passthrough.
N64 Joybus src/native/device/n64/ 1 joybus.pio Rumble feedback. Experimental.
Casio Loopy Loopy protocol src/native/device/loopy/ 4 loopy.pio Experimental.
Neo Geo / SuperGun GPIO src/native/device/gpio/ 1 None Active-low button output via GPIO pins.
NES Shift register src/native/device/nes/ 1 PIO NES controller emulation.
USB Device USB 2.0 HID src/usb/usbd/ 1 None 13 output modes (see below). Native USB controller.
BLE Peripheral BLE HID src/usb/usbd/ 1 None BLE gamepad emulation. Experimental.
UART Serial TX src/native/device/uart/ 1 None Serial bridge to external microcontrollers.

How Output Interfaces Work

Each output interface implements the OutputInterface struct:

typedef struct {
    const char* name;
    output_target_t target;
    void (*init)(void);
    void (*task)(void);
    void (*core1_task)(void);
    uint8_t (*get_rumble)(void);
    uint8_t (*get_player_led)(void);
} OutputInterface;
  • init() configures PIO programs, GPIO pins, or USB descriptors during startup.
  • core1_task() runs on Core 1 in a tight loop -- the timing-critical PIO interaction for console protocols. Only one output can claim Core 1.
  • task() runs on Core 0 each main loop iteration for non-timing-critical work (USB device polling, status updates).
  • get_rumble() and get_player_led() return feedback state that the player manager routes back to input controllers.

USB Device Output Modes

The USB device output supports 13 emulation modes, selectable at runtime via web config or button combo:

Mode Emulates Console Auth
SInput Joypad HID Gamepad --
XInput Xbox 360 Controller XSM3
DirectInput Generic HID Gamepad --
PS3 DualShock 3 --
PS4 DualShock 4 Passthrough
PS Classic PS Classic Controller --
Switch Nintendo Switch Pro Controller --
Xbox Original Controller S --
Xbox One Xbox One Controller --
XAC Xbox Adaptive Controller --
GC Adapter Wii U GameCube Adapter --
Keyboard + Mouse HID Keyboard and Mouse --
MIDI MIDI Controller --

Mode switching triggers USB re-enumeration. The selected mode persists to flash.

Related

  • GBA Link Cable — production GameCube→GBA controller mode (gc2usb autoboots an embedded payload onto a real GBA over the DOL-011 link cable; GBA reads back as a HID gamepad). Also covers the experimental USB-vendor bridge mode for a forked Dolphin (default-off, see doc for status).

Feedback

Console outputs can send feedback back to the input controllers:

  • Rumble: GameCube, Dreamcast, and N64 outputs forward motor commands. The player manager routes these to the correct physical controller (USB SET_REPORT, BT HID output report, N64 rumble pak).
  • Player LEDs: Some outputs report player numbers, which the player manager forwards to controllers that support player LEDs (Xbox, DualShock 4, DualSense).

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