USB Steering Wheel (Hori Racing Wheel Overdrive)¶

The SMCSKart bench uses a Hori Racing Wheel Overdrive for Xbox Series X as an operator input device. It is a USB HID device (not XInput-only), so it enumerates under the Linux xpad/HID gamepad driver without extra setup.

Identification¶

Field	Value
Vendor ID	`0f0d` (Hori Co., Ltd.)
Product ID	`0152`
Device name	`Hori Racing Wheel Overdrive for Xbox Series X`
USB interfaces	`ff47d0` (Xbox HID class)
Force feedback	Reported (`FF=107030000`) — not currently used

Wiring¶

The wheel plugs into the mainboard USB-A port (primary path), which routes to the Teensy 4.1 USB Host header. The Teensy firmware enumerates HID/XInput wheels via USBHost_t36 and drives logic from the wheel state directly.

A Raspberry Pi USB port is supported as a fallback path — useful when the Teensy USB Host cannot bind a specific device. In that mode wheel_bridge.py on the Pi forwards events to the Teensy over the Pi↔Teensy UART.

Linux device nodes¶

Node	Purpose
`/dev/input/js0`	Legacy joystick API — easy to consume with 8-byte `struct js_event` reads
`/dev/input/event5`	evdev API — richer event types, force-feedback output
`/dev/input/by-id/usb-HORI_*-joystick`	Stable symlink, prefer this over `js0`

Access requires membership in the input group (the gokart user is already a member).

Input map (observed via `wheel_probe.py`)¶

Axes (signed 16-bit, `-32768..+32767`)¶

#	Name	Resting	Description	Notes
0	LX	0	Steering wheel	Centered at 0, full left → negative, full right → positive. Physical lock-to-lock does not reach the extremes; treat the usable range as a tunable calibration.
1	LY	0	(unused)	No physical control mapped; stays at 0.
2	LT	-32767	Brake pedal	-32767 = released, +32767 = fully pressed.
3	RX	0	(unused)
4	RY	0	(unused)
5	RT	-32767	Throttle pedal	-32767 = released, +32767 = fully pressed.
6	HAT0X	0	D-pad horizontal	Three-state: -32767 / 0 / +32767.
7	HAT0Y	0	D-pad vertical	Three-state: -32767 / 0 / +32767.

Buttons (11 total, indexed 0–10)¶

Reported via the standard xpad gamepad mapping; the physical label depends on the wheel's face/paddles.

#	XInput label
0	A
1	B
2	X
3	Y
4	LB (left shoulder / paddle)
5	RB (right shoulder / paddle)
6	View / Select
7	Menu / Start
8	Xbox / Home
9	LSB (left stick press)
10	RSB (right stick press)

Data flow¶

Primary: mainboard USB-A → Teensy USB Host¶

Hori wheel --USB--> Mainboard USB-A --> Teensy 4.1 USB Host header
                                            |
                                            v
                            USBHost_t36 JoystickController
                                            |
                                            v
                           onboard LED + logic in kart_controller.ino

The firmware instantiates USBHost, two USBHubs, and a JoystickController, polled from loop() via serviceUsbHostWheel(). On connect it broadcasts INFO WHEEL_HOST_CONNECTED vid=… pid=… type=… to both the USB CDC serial and the Pi UART. While any button is held, the Teensy onboard LED (pin 13) lights.

Fallback: Pi USB → UART → Teensy¶

Hori wheel --USB--> Raspberry Pi --/dev/serial0, 115200 8N1--> Teensy 4.1
                       |                                            ^
                       v                                            |
         wheel_bridge.py reads /dev/input/js0       handles WHEEL_BTN command

Use this path when the Teensy USB Host cannot bind the device (e.g. if USBHost_t36 does not recognize a specific vendor variant). The Teensy ORs both sources, so the onboard LED responds to whichever path is delivering data.

Line protocol additions¶

WHEEL? — query host connection + current button state
Response: OK WHEEL host_connected=<0|1> [vid=… pid=… type=…] host_buttons=0x… pi_buttons=0x…
WHEEL_BTN <idx> <0|1> — button state change (Pi fallback path)
Example: WHEEL_BTN 0 1 / WHEEL_BTN 0 0
Idempotent; missed edges reconcile on the next change.

Bring-up¶

Mainboard path (preferred)¶

Plug wheel into the mainboard USB-A.
Over the Pi UART, send WHEEL? and look for host_connected=1 with the Hori VID/PID (0x0f0d / 0x0152).
Press any wheel button — the Teensy onboard LED (pin 13) should light. Watch for INFO WHEEL_HOST_CONNECTED … on first enumeration.

Pi fallback¶

Plug wheel into a Pi USB port. Verify lsusb | grep -i hori and ls /dev/input/js0.
Map inputs: python3 pi/wheel_probe.py. Ctrl+C prints a summary.
Run the bridge: python3 pi/wheel_bridge.py. Onboard LED responds as above.