CAN Analyzer

This guide is applicable to the following device / devices:

TMU CM4

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The CAN Analyzer in the AutoPi Cloud is an interactive tool for discovering, testing, and validating CAN bus communication on a connected vehicle or machine. It provides a UI-based interface for running low-level CAN/OBD commands, monitoring raw traffic, and validating protocol configurations before deploying loggers or integrations.

This tool is primarily used during initial setup, troubleshooting, reverse engineering, and integration validation.

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Overview

The CAN Analyzer enables:

• Passive listening of CAN traffic (sniffing)
• Testing different CAN protocols and baud rates
• Sending diagnostic requests (PID / UDS / J1939)
• Recording and replaying CAN messages
• Verifying communication between AutoPi and ECU(s)

It acts as a real-time inspection layer between the AutoPi device and the vehicle network.

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Interface Structure

The CAN Analyzer page consists of four main tabs:

1. Sniffer - passive monitoring of CAN traffic.
2. Recorder - captures CAN messages and stores them for later use.
3. Player - replays previously recorded CAN traffic.
4. PID Tester - sends request-response queries to ECUs.

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Sniffer (Passive CAN Monitoring)

Note: This will only work on vehicles which allow direct CAN streaming.

Purpose

Used to detect:

• Active CAN bus.
• Correct protocol and baud rate.
• Raw CAN messages.

How it works

The sniffer runs a passive monitor similar to:

obd.monitor duration=5 protocol=<protocol> baudrate=<baudrate>

This listens to all CAN frames being broadcast on the bus. This is required because:

• Some vehicles stream data continuously.
• Others only respond to requests (PIDs).

Configuration

Field	Description
Vehicle Bus	Select CAN interface (auto or manual)
Protocol	CAN protocol (e.g. ISO 15765-4, J1939)
Baud Rate	Typical values: 125k, 250k, 500k
Duration	Capture time in seconds

Workflow

1. Start with Auto Vehicle Bus or a known protocol.
2. Click Sniff.
3. Observe output:
   • No data → wrong configuration.
   • Data present → valid configuration.
4. If you didn't receive any data in the output field, adjust the protocol and/or baud rate until consistent data is received.
5. You can also use Verify Connection when an obd request is send to the vehicle and device awaits for the response, as a second layer of verification of the correct connection setup.
6. Create bus, if you are sure of a Vehicle Bus used by your vehicle.

This process is essential when:

• Vehicle protocol is unknown. You can read more here: Setting up CAN Bus Protocol.
• Working with heavy-duty (J1939) or proprietary buses. You can read more here: Heavy Duty Vehicles/ J1939 Protocol.

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Recorder

Purpose

Stores CAN traffic for:

• Offline analysis
• Debugging intermittent issues
• Sharing datasets

Backend equivalent:

can.dump duration=10 file=test.log

This captures raw CAN frames to files such as .log, .csv, or .blf

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Player

Purpose

Replays recorded CAN data onto the bus.

Use cases

• Simulate ECU behavior
• Test integrations without a live vehicle
• Reproduce issues from recorded sessions

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PID Tester (Active Requests)

Purpose

Send request-response messages to ECUs.

Example:

obd.query rpm mode=01 pid=0C

This requests engine RPM from the ECU.

When to use

Use PID Tester when:

• Data is not broadcast automatically.
• Specific signals are required.
• Validating diagnostic communication.

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Terminal Integration

All actions in the CAN Analyzer correspond to terminal commands.

Example:

obd.dump protocol=6 baudrate=500000 duration=1

This allows:

• Reproducibility.
• Automation via scripts.
• Debugging outside the UI.

Typical Use Cases

1. Protocol Detection - identify correct CAN configuration by testing:

   • Protocol
   • Baud rate.

2. Vehicle Integration - verify that:

   • AutoPi can access CAN data
   • ECUs respond correctly.

3. Reverse Engineering - analyze unknown CAN signals by:

   • Sniffing traffic
   • Correlating values with real-world behavior.

4. Troubleshooting - detect issues such as:

   • No CAN traffic
   • Incorrect wiring
   • Unsupported protocol

5. Development & Testing

   • Validate CAN-based applications
   • Simulate environments using Player

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Summary

The CAN Analyzer is a diagnostic and validation tool that sits between raw CAN access and production logging. It allows you to:

• Discover how a vehicle communicates
• Validate configurations before deployment
• Debug issues at the lowest level
• Build reliable CAN-based solutions on top of AutoPi

It is typically the first step in any CAN integration workflow.

Important Notes

• Requires vehicle support for CAN access (OBD or direct wiring)
• Ignition needs to be ON
• Some vehicles require wake-up communication
• Avoid testing on moving vehicles

Best Practice Workflow

• Ensure device is powered on and online
• Start with Sniffer:
  • Test common baud rates (250k / 500k)
• Identify working configuration
• Use PID Tester to validate responses
• Record traffic if needed
• Build loggers or integrations based on findings