IMU Calibration

The IMU Calibration module (imu_cal.c) is responsible for re-zeroing and configuring the external 6-axis IMU sensor via the CAN bus.

Calibration Sequence

When a recalibration is requested (typically via a dashboard input mapped to can_rx_data.dash_inputs.IMU_Recal), the module executes a 5-step sequence targeting CAN ID 0x050:

1. Step 0 (0 ms): Unlock Configuration.
2. Step 1 (+200 ms): Enable 6-Axis mode.
3. Step 2 (+200 ms): Start acceleration calibration.
4. Step 3 (+6.6 s): Exit calibration mode.
5. Step 4 (+200 ms): Reset heading (yaw).

CAN Bus Timing

To ensure the calibration commands are not lost or corrupted by dense CAN traffic, the imu_cal_tick() function carefully orchestrates the transmission. It monitors the time elapsed since the last incoming IMU frame. It waits for a specific "quiet window" (between 4ms and 14ms since the last frame) to dispatch the outgoing calibration command, ensuring it sneaks in between the IMU's high-frequency broadcast bursts.