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Message Map - BusFrame ID Registry

This document defines every frame ID in the system, its expected DLC, encoding, and purpose. All IDs are centrally declared in the FrameId enum in include/hal.h.

Frame ID Table

ID (hex) Enum Name DLC Direction Description
0x100 FRAME_ID_SENSOR 8 RX Primary sensor data frame
0x10E FRAME_ID_SENSOR_ERROR 1 RX Sensor error / diagnostic frame
0x110 FRAME_ID_SENSOR_TEMP_B 2 RX Redundant temperature channel B

Sensor Frame (0x100) Payload Layout

Byte Field Encoding
0–1 RPM uint16 big-endian, raw RPM
2–3 Temperature uint16 big-endian, (temp+50)*10
4–5 Oil Pressure uint16 big-endian, oil*100
6 Running Flag 0 = stopped, 1 = running
7 Checksum XOR of bytes 0–6

Sensor Error Frame (0x10E) Payload Layout

Byte Field Encoding
0 Error code Application-specific byte

Temperature Channel B Frame (0x110) Payload Layout

Byte Field Encoding
0–1 Temperature B uint16 big-endian, (temp+50)*10

Unknown Frame Handling

Any frame with an ID not listed above is rejected by hal_ingest_sensor_frame() with STATUS_INVALID_ARGUMENT and a structured error diagnostic is recorded.

DLC Validation

DLC is validated per frame ID using hal_expected_dlc_for_id(). A valid ID with the wrong DLC is also rejected with STATUS_INVALID_ARGUMENT.