CAN communication

Linux CAN communication

CAN communication is a very common bus communication method in robotics, vehicles, industrial control, and motor drives.

Compared to serial communication, CAN is better suited for multiple devices communicating on the same bus. For example, in a robot chassis, multiple motor drivers, a chassis control board, and sensor nodes may all be connected to the CAN bus.

In practical projects, CAN communication is common in:

• Control motor driver
• Read motor encoder feedback
• Connect the chassis control board
• Communication between multiple control nodes
• Vehicle bus communication
• Industrial equipment and motion control systems

For areas such as mobile robot chassis, motor control, and autonomous driving by-wire systems, CAN is a very important type of communication method.

What is CAN communication?

CAN, full name Controller Area Network, is a multi-master bus communication protocol.

Unlike serial point-to-point communication, multiple nodes can be connected to the CAN bus. Each node can send messages, and other nodes determine whether to process the message based on the CAN ID.

Common concepts in CAN communication include:

In Linux, CAN devices are usually not device files like /dev/ttyUSB0, but are abstracted into network interfaces, for example:

can0

You can view it with the following command:

ip link

Common CAN Tools and Libraries for Linux

The core of CAN communication on Linux is SocketCAN.

SocketCAN is a CAN communication framework provided by the Linux kernel. It abstracts CAN devices into a form similar to network interfaces, for example can0, can1.

Common tools and libraries include:

Comparison of Solutions

This tutorial recommends selecting

This tutorial recommends prioritizing:

SocketCAN + can-utils

The reason is:

• SocketCAN is the standard solution for CAN communication on Linux.
• Independent of ROS 2, suitable for regular C++, OpenCV, Qt, embedded Linux projects
• can-utils is very suitable for debugging and verifying CAN devices.
• Later, it can be packaged as a standard C++ driver.
• Can naturally integrate with ros2_control hardware_interface

The recommended learning order is:

1. 使用 ip link 配置 can0
2. 使用 candump 接收 CAN 帧
3. 使用 cansend 发送 CAN 帧
4. 理解 struct can_frame
5. 使用 C++ SocketCAN 进行收发
6. 封装自己的 CanDriver 类
7. 接入 ROS 2 或 ros2_control

The recommended project structure is:

上层项目：ROS 2 / OpenCV / Qt / 普通 C++ 程序
        ↓
自己封装的 CanDriver 类
        ↓
SocketCAN
        ↓
can0
        ↓
电机驱动器 / STM32 / 底盘控制板

Relationship with ROS 2

Learning SocketCAN doesn't mean you don't need ROS 2.

In a ROS 2 project, you can encapsulate CAN communication as a regular C++ class, then use it in a ROS 2 node or ros2_control hardware_interface.

For example:

ros2_control controller
        ↓
hardware_interface
        ↓
自己封装的 CanDriver
        ↓
SocketCAN
        ↓
can0
        ↓
电机驱动器

The advantage of this approach is that the CAN communication code is not tightly coupled with ROS 2. Even when working on standard C++ projects, Qt host computer applications, or OpenCV control programs in the future, the same CAN driver can still be reused.

When to use ros2_socketcan

ros2_socketcan is not unusable.

If the project itself is a pure ROS 2 architecture, and you want to quickly convert CAN frames into ROS 2 topics, then ros2_socketcan is an option worth considering.

However, for learning low-level drivers and long-term engineering reuse, it is still recommended to first master SocketCAN.

It can be understood this way:

SocketCAN：底层能力
ros2_socketcan：ROS 2 封装

First learn SocketCAN, then it will be easier to understand ros2_socketcan.

When to use ros2_canopen

If your motor driver or industrial device uses the CANopen protocol, you can’t just treat it as ordinary CAN frame communication.

CANopen is a high-level protocol built on top of CAN, involving concepts such as object dictionary, PDO, SDO, NMT, etc.

In this case, consider learning:

ros2_canopen

But if your device only uses a custom CAN protocol, such as defining your own CAN IDs and data formats, then prioritizing learning SocketCAN is sufficient.

Chapter learning objectives

After completing this chapter, you should be able to:

• Basic concepts of CAN communication
• How to use the can0 device on Linux
• Configure CAN baud rate using ip link
• Use candump and cansend to debug the CAN bus
• Understand concepts such as CAN ID, standard frame, extended frame, data field, etc.
• Sending and Receiving CAN Frames Using C++ SocketCAN
• Encapsulate CAN communication into reusable C++ classes
• Lay the foundation for subsequent integration with ROS 2, ros2_control, and motor driver control.