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How to Read and Decode CAN Bus Data Step by Step

Updated at 19 Jun, 2024

— Discover how to read and decode CAN bus data. This guide covers extraction, interpretation, and tools, simplifying mastery for both beginners and pros.

How to Read and Decode CAN Bus Data Step by Step

Reading CAN bus data is essential for vehicle diagnostics, industrial automation, and more.

This guide will equip you with the knowledge and tools needed to effectively interpret CAN bus data.

With 20 combined years of experience in CAN bus technology, we’ll provide expert insights and practical steps to ensure you master this crucial skill.

In other words, we know what we're doing (we think).

Let's get to it.

What is CAN bus Data?

CAN (Controller Area Network) bus data is a robust vehicle bus standard designed to allow microcontrollers and devices (also known as small computers and sensors) to communicate with each other without a host computer.

It is extensively used in automotive applications and many other areas.

The data transmitted via CAN bus includes various signals such as speed, RPM, and diagnostic information. Understanding these signals is crucial for interpreting vehicle performance and diagnostics, but extracting the data and having the right infrastructure to interpret it is just as important.

Logging CAN bus data isn't limited to regular vehicles. It's also used in heavy-duty vehicles, tractors, and other machinery, which often use specialized sub-CAN systems like J1939 and ISO 11783. Extracting and interpreting this data allows for comprehensive monitoring and diagnostics in these varied applications.

According to the Society of Automotive Engineers (SAE), CAN bus data has significantly improved vehicle diagnostics, maintenance, and automation, leading to enhanced performance and safety across various applications.

The basics of the CAN bus Protocol

Understanding the CAN bus protocol is essential for reading CAN bus data accurately. The protocol ensures reliable data transmission between microcontrollers and devices, coordinating various functions within vehicles and machinery.

Think of a CAN bus message like a postcard you send to a friend. Here are the key parts:

  • Identifier (ID): This is like the address on the postcard. It tells the system who the message is for and its priority. Higher priority messages (like urgent news) have lower ID numbers and get delivered first.

  • Data Field: This is the main message on the postcard. It contains the actual information, such as speed or RPM, and can be up to 8 bytes long.

  • CRC Field: Think of this as a spell-checker. It ensures the message isn't corrupted by checking for errors.

The connection between a CAN bus message and CAN bus data is straightforward: the message carries the data. The data field within each CAN bus message holds the information you need to read and interpret. Whether it's the speed of a vehicle or the status of a sensor, this data is embedded in the messages transmitted across the CAN bus network.

These basics help you get started with reading CAN bus data. If you want a deeper dive into how the CAN bus system works, check out our comprehensive blog post on the subject here.

Tools and Equipment Needed to Read CAN bus Data

To read CAN bus data effectively, you'll need a few essential tools and equipment. These tools will help you connect to the CAN bus network, extract the data, and interpret it correctly.

Tool/Equipment Description
1. Can bus Interface A CAN bus interface is a device that connects to the CAN bus network and allows you to read the data. Examples include the AutoPi interface, USB CAN interfaces, and standalone CAN analyzers. Find the perfect CAN bus interface.
2. Software You’ll need software to interpret the data from the CAN bus interface. Popular options include SavvyCAN, CANalyzer, and others. This software helps decode the messages and display the data in a readable format.
3. Cables Various cables are needed to connect the CAN bus interface to the CAN network and your computer. Ensure you have the right connectors for your specific setup.
4. CAN bus Decoder A CAN bus decoder is either a feature within your software or a separate tool that translates the raw CAN bus messages into human-readable data. This is essential for understanding the information transmitted by the CAN bus.
5. CAN Logger A CAN logger is a device that records CAN bus data over time. This is useful for analyzing trends, diagnosing intermittent issues, and reviewing historical data.

Think of these tools like a toolkit for a car mechanic. Just as a mechanic needs wrenches, diagnostic tools, and manuals to fix a car, these tools help extract and understand the data.

At AutoPi, we use a combination of reliable CAN bus interfaces, such as our own AutoPi dongle, along with powerful software tools to read and log CAN bus data. For more details on how we log raw CAN messages, you can refer to our detailed documentation page.

The autopi dongle with the autopi cloud behind it

Set Up and Connect Your CAN bus Tool

To read CAN bus data, it's essential to set up your CAN bus reading tool correctly and connect it to the CAN bus network.

Here’s a step-by-step guide to help you get started.

Step 1: Install the Software

  1. Download and Install: First, download the appropriate software for your CAN bus interface. Popular options include the ones mentioned above. This software is crucial because it interprets the raw data from your CAN bus interface into a readable format.

  2. Configure the Software: Follow the installation instructions provided by the software, and configure it to recognize your CAN bus interface. This ensures that the software and hardware can communicate effectively.

Step 2: Connect the Interface

  1. Locate the OBD-II Port: In most vehicles, the OBD-II port is found under the dashboard near the driver's seat. For heavy-duty vehicles and machinery, refer to the user manual to locate the CAN bus connector.

  2. Plug in the Interface: Connect your CAN bus interface to the OBD-II port or the appropriate CAN bus connector using the necessary cables. This physical connection allows your interface to access the CAN bus network and read data from it.

  3. Verify the Connection: Ensure the interface is securely connected and recognized by the software to avoid any data transmission issues.

Step 3: Configure the CAN Bus Interface

  1. Set Parameters: Open your CAN bus reading software and configure the interface parameters such as bit rate and CAN ID filters. Setting these parameters correctly ensures the software reads the appropriate data from the CAN bus network.

  2. Test the Connection: Use the software’s testing feature to verify that data is being transmitted and received correctly. This ensures your setup works as intended.

Step 4: Start Reading and Interpreting CAN Bus Data

  1. Monitor the Data: Begin monitoring the incoming CAN bus data through the software. The software will display messages with IDs and data fields.

  2. Interpret the Data: Use the software’s decoding feature to interpret the CAN bus messages. For instance, a message with ID 0x123 might represent vehicle speed, while another with ID 0x456 could indicate engine RPM. Understanding these messages allows you to gain insights into the vehicle’s performance.

  3. Log the Data: Use a CAN logger to record data over time, which is useful for analyzing trends and diagnosing intermittent issues.

Skip the Setup: Use AutoPi

If you want to bypass the manual setup process, consider using the AutoPi device, a highly customizable tool that provides a direct interface to your car and communicates seamlessly with the ECU. The AutoPi simplifies the process, making it user-friendly.

Connecting the AutoPi Device

  1. Plug in the Device: Connect the AutoPi device to your vehicle’s OBD-II port. This establishes a direct connection with the vehicle's CAN bus network.

  2. Power Up: Turn on your vehicle to power the AutoPi device. This step ensures the device is operational and ready to interface with the network.

  3. Connect to AutoPi Cloud: Use your computer or smartphone to connect to the AutoPi Cloud platform. This platform allows you to configure and monitor your device remotely.

  4. Configure Settings: Follow the on-screen instructions to configure your settings and start monitoring your vehicle’s data. This makes sure everything is set up correctly for your specific needs.

At AutoPi, we use a straightforward approach to set up and connect our CAN bus interfaces. For more detailed instructions, refer to our Getting Started Guide.

Reading and Interpreting CAN bus Data

Now that you have set everything up, understanding your CAN bus data is where things get interesting.

Vehicle data is essentially CAN bus data because it includes all the crucial information transmitted within your vehicle’s network. This data includes engine performance, fuel consumption, speed, and more, all communicated through the CAN bus system.

By reading and interpreting this data, you can unlock valuable insights to optimize your vehicle’s performance and maintenance.

Reading CAN bus data can be a game changer for both individual car owners and businesses. It helps in identifying potential issues before they become serious problems and optimizes overall efficiency.

Whether you're a car enthusiast or a fleet manager, understanding CAN bus data offers significant advantages.

Use Case Examples

Let's take a look into a few use cases from our clients, who manages a fleet of delivery trucks and rental cars. They have been using a the AutoPi CAN bus interface and software to log and analyze data from their vehicles.

Here's how they make sense of this data:

Improved fuel efficiency
Aspect Details
Data Received CAN bus ID 0x201 (fuel consumption), Data Field: [0x12, 0x34] (hexadecimal representing liters per hour).
Configuration Set up the trigger to log fuel consumption data every minute.
Reading the Data Convert the hexadecimal values to readable numbers (e.g., 0x1234 = 4660 in decimal, meaning 46.60 liters per hour).
Understanding the Data Analyze the logged data to find patterns. The client notices that trucks idle for long periods, leading to inefficient fuel use.
Action Taken Implement a policy to reduce idling time, resulting in a 15% reduction in fuel costs across their fleet.

Improved vehicle uptime
Aspect Details
Data Received CAN bus ID 0x302 (engine temperature), Data Field: [0x78] (hexadecimal representing degrees Celsius).
Configuration Set up alerts for engine temperature exceeding 90°C.
Reading the Data Convert the hexadecimal value to a readable number (e.g., 0x78 = 120 in decimal, meaning 120°C).
Understanding the Data The software alerts the team when temperatures rise above the threshold, indicating a potential issue.
Action Taken Schedule maintenance before the engine overheats, reducing repair costs by 20%.

Promoted better driver safety
Aspect Details
Data Received CAN bus ID 0x450 (vehicle speed), Data Field: [0x30] (hexadecimal representing km/h).
Configuration Log vehicle speed data every second.
Reading the Data Convert the hexadecimal value to a readable number (e.g., 0x30 = 48 in decimal, meaning 48 km/h).
Understanding the Data Identify patterns of harsh braking and speeding by analyzing speed changes over time.
Action Taken Implement a driver training program to promote safer driving habits, resulting in a 10% improvement in vehicle safety and reduced wear and tear.

The insights gained from CAN bus data enables businesses to optimize their operations, reduce costs, and improve safety. These benefits are not limited to large fleets; individual car owners can also leverage CAN bus data to keep their vehicles running smoothly and efficiently.

Analyze CAN Bus Data Like a Pro

Once you’ve mastered the basics of reading CAN bus data, you can take your analysis to the next level with advanced techniques such as data logging, real-time monitoring, and setting custom alerts. These techniques provide deeper insights and allow for proactive vehicle management.

All of this happens seamlessly through the AutoPi Cloud, transforming raw CAN data into actionable insights effortlessly. Discover how AutoPi can revolutionize your vehicle management with unparalleled ease and efficiency. Learn more here.

Screenshot of a terminal displaying hexadecimal CAN bus data sequences.


Understanding and interpreting CAN bus data is a powerful tool for optimizing vehicle performance, ensuring safety, and reducing operational costs. Whether you are an individual car owner or manage a fleet of vehicles, the insights gained from CAN bus data can significantly enhance your vehicle management capabilities.

With tools like AutoPi, accessing and utilizing this data becomes straightforward and efficient. From basic data reading to advanced analysis techniques, AutoPi provides everything you need to turn raw CAN data into valuable information.

Ready to transform your vehicle management practices with the power of CAN bus data? Contact us today to learn more about how AutoPi can help you achieve your goals.

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