CAN Message Handling

The CAN Message Handling module (can_comm.c) acts as the interpreter between the raw CAN bus data and the ECU's internal representations. It utilizes a ring buffer provided by the generic_can_driver.

Receiving Messages (process_can_frames)

The process_can_frames function empties the RX ring buffer, inspecting the CAN ID of each message to unpack its payload into the global can_rx_data structure.

Key Incoming Messages

CAN ID	Source	Description	Variables Updated
0x050	Telemetry/IMU	Custom IMU message containing acceleration, gyro, and Euler angles.	imu_data
0x0A0	Front Gateway	Front wheel speeds and suspension travel.	gf_wheel_sensors
0x0A1	Front Gateway	Accelerator Pedal Position (APPS), Steering Angle, and R2D Button status.	gf_misc_sensors
0x0B0	Rear Gateway	Rear wheel speeds and suspension travel.	gr_wheel_sensors
0x0B1	Rear Gateway	Brake pressure, Junction Box (JB) currents, and SDC status.	gr_misc_sensors
0x0B2	Rear Gateway	Cooling flow rate and temperatures.	gr_liquid_sensors
0x021	Left Inverter	Motor temp, Inverter temp, and feedback inputs.	gil_inv_data_2
0x031	Right Inverter	Motor temp, Inverter temp, and feedback inputs.	gir_inv_data_2
0x010	BMS	Battery Management System errors and temperatures. Maps complex bitfields to local faults (can_ams_fault).	bms_errors_temps
0x011	BMS	SOC and Voltage data.	bms_soc_voltage
0x014	BMS	Battery Current and Discharge limits.	bms_current
0x0D0	Dashboard/Telemetry	Driver inputs (e.g., Recalibration requests, Motor Control Mode toggle).	dash_inputs
0x0D1	Dashboard/Telemetry	Slip control PID gains override.	dash_pid_tune_1
0x0D2	Dashboard/Telemetry	Torque Vectoring (TV) PID gains override.	dash_pid_tune_2
0x0F0	GPS	GPS speed, course, and yaw angle.	gps_angles

Fault Handling on RX

• If the SDC value in message 0x0B1 reads as 0, a can_sdc_fault is flagged.
• If the BMS reports any critical fault in message 0x010 (e.g., Low Cell Voltage, Pack Too Hot), a can_ams_fault is flagged, and the physical AMS_ERROR_Pin is driven low.

Sending Messages (set_can_frames)

The set_can_frames function packs the most recent internal data into the transmit ring buffer.

Key Outgoing Messages

Transmit Buffer Index	Description	Payload Data
0	Inverter Commands (0x0E0)	Motor Enable/Disable state, L/R Regen percentages, L/R Speed percentages, and Calculated Vehicle Speed.
1	Rear Gateway Commands (0x0E5)	Signals the Rear Gateway to turn the R2D Buzzer On/Off.
6	UKF State (0x...)	Unscented Kalman Filter estimates for Velocity X, Side Slip, Rotation Z, and Angular Velocity Z.
7	UKF Acceleration (0x...)	Unscented Kalman Filter estimates for Acceleration X and Y.
8	TV State Debug (0x...)	Torque Vectoring state, delta moment Z (delta_Mz), and slip control state.
9	Slip Control Debug (0x...)	Reference slip ratios (kappa_ref) and maximum torques (tmax) for left and right wheels.