Author: Mikayla Lee

CAN

AER Telemetry over CAN ISO-TP

CAN ISO-TP Telemetry Receiver & Test Pipeline

Overview

This system receives telemetry data from the motor controller over CAN using ISO-TP, decodes the packet into strongly typed data, and forwards it for downstream processing. It also includes test utilities for transmitting and validating telemetry over a virtual CAN interface (vCAN) in CI.

Workflow

CAN ISO-TP Data Reception

• Listens on the physical CAN interface (can0) using ISO-TP sockets
• Receives multi-frame telemetry packets from the motor controller
• Validates packet length (expected: 58 bytes)
• Decodes raw bytes into typed telemetry fields

Telemetry Parsing

• Converts byte slices into numeric values (f32, i32) using little-endian decoding
• Maps state and mode bytes into enums representing motor and MCU state machines
• Parses fault flags into boolean values
• Assembles all decoded values into a TelemetryData structure

Telemetry Forwarding

• Wraps decoded values in a TelemetryData struct
• Publishes telemetry via send_message()
• Uses the “telemetry” topic for downstream consumers

ISO-TP Test Transmission (vCAN)

• Serializes TelemetryData using bincode
• Sends telemetry as a single ISO-TP packet over vcan0
• Used exclusively for testing and CI validation

Key Features

• Strongly Typed Telemetry – Enums and structs ensure safe decoding of MCU and motor states
• Resilient Socket Handling – Automatically retries socket creation on failure
• Clear Packet Contract – Enforces a strict 58-byte telemetry frame layout
• CI-Friendly Testing – vCAN-based tests run in GitHub Actions
• Extensible Design – New telemetry fields and enums can be added with minimal refactoring

Telemetry Data Summary

Struct: TelemetryData

Purpose: Represents a fully decoded MCU telemetry packet received over CAN ISO-TP

Contents:

• Driver input: accelerator pedal travel (apps_travel)
• Motor metrics: speed, torque, max torque, direction, state
• MCU status: main state, work mode, voltage, current
• Thermal data: motor and MCU temperatures
• Fault flags: over-voltage, over-current, stall, phase current, overspeed
• Warning level: MCU warning severity
• Debug channels: debug_0 – debug_3

Enum Definitions

MotorState

• Off
• Precharging
• Idle
• Driving
• Fault

MotorRotateDirection

• Standby
• Forward
• Backward
• Error

MCUMainState

• Standby
• Precharge
• PowerReady
• Run
• PowerOff

MCUWorkMode

• Standby
• Torque
• Speed

MCUWarningLevel

• None
• Low
• Medium
• High

Each enum includes a from_byte() constructor for safe decoding from raw CAN payloads.

CAN Reader Summary

Function: read_can

Purpose: Continuously reads and decodes telemetry packets from can0

Workflow:

• Attempts to open an ISO-TP socket (retries on failure)
• Reads incoming packets asynchronously
• Validates packet length
• Parses raw bytes into TelemetryData
• Forwards decoded telemetry via send_message()

Error Handling:

• Logs socket creation failures
• Logs malformed packet lengths
• Continues operation without crashing

Test: ISO-TP Telemetry Transmission

Test: test_send_telemetry_over_isotp

Purpose: Verifies ISO-TP telemetry transmission over a virtual CAN interface

Steps

1. Prepare Test Data

• Creates a TelemetryData instance with representative values

2. Send Telemetry

• Serializes the struct using bincode
• Transmits the packet over ISO-TP on vcan0

3. Validate Environment

• Uses vCAN setup provided by the GitHub Actions workflow (test.yml)
• Confirms ISO-TP send path functions correctly

Key Points

• Uses tokio_socketcan_isotp for asynchronous CAN ISO-TP communication
• Clean separation between production (can0) and test (vcan0) interfaces
• Designed for reliability in embedded deployment and CI environments
• Documentation aligns directly with packet structure and test behavior