Hori Wheel & Pedals¶

The primary in-seat driver input is a Hori Racing Wheel Overdrive (a USB HID racing wheel with a throttle and brake pedal set). It plugs into the mainboard's USB-A port, which routes to the Teensy USB host header. The Teensy enumerates it with the USBHost_t36 library and reads the axes and buttons directly — the wheel is on the motion-authority computer, not the Pi.

Vendor / product: 0f0d:0152 (Hori). Enumerates through USBHost_t36 as an Xbox-One controller (joystickType 3).
On connect, the Teensy prints INFO WHEEL_CONNECTED vid=… pid=… type=… to both its USB serial and the Pi UART.

Two different input maps — use the Teensy one

The Linux js/evdev map in the hardware note Hori Wheel (hardware) is not the same as the map the Teensy sees through USBHost_t36. The triggers are 0…1023 unsigned (not ±32767) and the indices are shifted. The Teensy map below is authoritative for firmware behavior; the js map only applies to the (legacy) Pi-USB fallback path. Always re-confirm with the WHEELRAW command if the wheel firmware or library version changes.

Axis map (Teensy `USBHost_t36`)¶

Axis	Control	Range	Used for
0	Steering wheel	`-32768` (full left) … `+32767` (full right), centered at 0	Steering setpoint
3	Brake pedal	`0` released … `1023` pressed	Brake
4	Throttle pedal	`0` released … `1023` pressed	Throttle

The steering axis rarely reaches the raw extremes (mechanical lock is inside the electrical range), so the usable range is treated as a calibration. The pedal calibration (released = 0, pressed = 1023) plus a 3 % deadband and a plausibility margin are configured in firmware/kart-core/src/config.h and can be adjusted live with the CFG command.

Button map (Teensy `USBHost_t36`)¶

The Hori reports its face buttons on consecutive bits and its paddles on bits 12/13:

Bit	Physical control	Function
12	Left shift paddle	Downshift one gear
13	Right shift paddle	Upshift one gear
6	X face button	Backup: in DRIVE → disarm; in FAULT → clear (DRIVE entry is automatic, so this is not needed to drive)
5	B face button	Disarm / turn off (controlled stop → SAFE)
4 / 7	A / Y face buttons	(unused)

How the pedals become motion¶

flowchart LR
    thr["Throttle axis (0..1023)"] --> map["PedalMap:<br/>deadband + scale → 0..100%"]
    map --> gate{"DRIVE &amp; not Park<br/>&amp; not braking?"}
    gate -->|yes| dac["MCP4725 DAC → ESC"]
    gate -->|no| zero["0 (idle voltage)"]
    brk["Brake axis (0..1023)"] --> bmap["PedalMap → 0..100%"]
    bmap --> bthr{"> 20% ?"}
    bthr -->|yes| brake["Assert ESC regen brake<br/>(overrides throttle)"]

Details for each path:

Throttle is deadbanded and scaled to 0–100 %, then written to the throttle DAC — but only while the state machine is in DRIVE, the gear is not Park, and the brake is not engaged. See Throttle.
Brake is treated as a switch: past 20 % pedal travel the ESC's regen brake line is held, and brake always overrides throttle. See Brake.
Steering maps the wheel axis to an angle setpoint sent to the Steervo over CAN. See Steering Overview.
Gears are changed with the paddles. See Reverse & Gearshifting.

Plausibility¶

Each pedal reading is range-checked against its calibration plus a margin. A reading that stays implausible (both extremes / out of range) for longer than a debounce window (250 ms) raises a pedal-implausible fault and triggers a controlled stop. This catches a disconnected or shorted pedal signal.

Arming with the wheel (the ARM chord)¶

In a normal (in-seat) build, the driver arms the kart with a deliberate chord rather than a single button, so it can't happen by accident:

ARM chord

Hold both shift paddles (bits 12 + 13) and press the brake pedal, with the throttle released, for 1 second, while the kart is in SAFE and stopped. This transitions SAFE → ARMED, which begins the precharge → contactor sequence.

DRIVE then follows automatically once the bus is charged and the throttle DAC is alive — there is no separate "go" button. The gear ladder starts in Park (throttle inhibited) so the driver must deliberately upshift into a drive gear before any throttle is delivered.

To turn off: press B, or send DISARM from the dashboard/serial — either performs a controlled stop back to SAFE.

Diagnostics¶

WHEELRAW (serial) dumps the live axis values, button mask, and joystick type — use it to confirm the map and pedal ranges.
WHEEL? reports host connection state and button state.

USB host re-enumeration after a reflash

A Teensy reboot leaves an already-connected wheel dark. After flashing, hot-plug the wheel (or power-cycle the board) so the USB host re-enumerates it. Confirm with WHEELRAW showing enum=1.

Legacy Pi-USB fallback¶

The wheel can alternately be plugged into a Raspberry Pi USB port, with pi/wheel_bridge.py forwarding button events to the Teensy over the UART (WHEEL_BTN commands). This path uses the Linux js map and is a fallback for when the Teensy USB host cannot bind a device. The primary and normal path is USB-host-direct to the Teensy.