CAN

1 CAN Bus Overview

The CAN bus protocol (Controller Area Network) is a serial communication protocol bus developed by BOSCH (Bosch) of Germany in 1986. The GM-3568JHF development board is equipped with 2 CAN interfaces, implemented based on the integrated CAN controller of the RK3568J processor, providing a reliable communication solution for industrial control, automotive electronics, and device interconnection.

1.1 CAN Bus Technical Features

ParameterSpecification
Protocol StandardISO 11898-1 (CAN 2.0A/2.0B)
Number of Interfaces2 independent CAN interfaces
Transmission MediumTwisted pair
Network TopologyBus type
Transmission DistanceUp to 1000 meters (5Kbps)
Maximum Number of Nodes110 nodes
Data Frame Length0-8 bytes
Arbitration MechanismNon-destructive bit arbitration

1.2 CAN Protocol Features

Technical Advantages

  • Multi-master Communication: Supports multiple nodes sending data simultaneously
  • Non-destructive Arbitration: High-priority messages are transmitted first
  • Error Detection: Powerful error detection and handling mechanism
  • Strong Real-time Performance: Deterministic message transmission delay
  • High Reliability: Differential signal transmission, strong anti-interference ability

Application Fields

  • Automotive Electronics: Engine management, body control, instrumentation systems
  • Industrial Automation: PLC control, sensor networks, actuator control
  • Medical Equipment: Medical instrument interconnection, monitoring equipment communication
  • Marine Systems: Navigation equipment, power system control
  • Building Automation: Lighting control, air conditioning systems, security equipment

2 GM-3568JHF CAN Interface Configuration

According to the product specifications, the GM-3568JHF development board provides 2 CAN interfaces to meet a variety of industrial application requirements.

2.1 CAN Hardware Connection

The CAN wiring between the development board and external devices is as follows:

Development BoardExternal Device
CAN_LCAN_L
CAN_HCAN_H
CAN

2.2 CAN Communication Test

This test uses a CAN analyzer. Connect the H and L terminals of the two devices

CAN_2

Check the Interface

Check whether the can0 and can1 interfaces are generated on the development board

root@linaro-alip:/# ifconfig -a
can0: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 54

can1: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 55
···

Parameter Settings

Set the baud rate on the development board and perform a test (CAN0 is used as the test sample here)

# 将 CAN0 接口关闭
sudo ip link set can0 down
# 设置比特率为 250000
sudo ip link set can0 type can bitrate 250000
# 将CAN0 接口启用
sudo ip link set can0 up

# 发送（标准帧,数据帧,ID:7ff,date:11223344556677）
cansend can0 -i 0x7ff 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88

# 接收
candump can0

Test Results

  • Development board test result:
CAN_3
  • CAN analyzer test result:
CAN_4

3 CAN Network Diagnostics and Debugging

3.1 Using cansniffer for Network Analysis

# 安装 cansniffer
sudo apt-get install can-utils

# 启动网络嗅探
cansniffer can0

# 带过滤的嗅探
cansniffer can0 -c 0x100-0x200

# 保存日志
candump can0 -L > can_log.txt

3.2 Network Load Test

# 生成测试流量
cangen can0 -g 10 -I 123 -L 8

# 测试网络带宽
canbusload can0@250000

# 压力测试
for i in {1..1000}; do
    cansend can0 123#DEADBEEF
done

4 Troubleshooting

4.1 CAN Interface Cannot Start

Inspection Steps:

# 检查内核模块
lsmod | grep can

# 手动加载 CAN 模块
sudo modprobe can
sudo modprobe can-raw
sudo modprobe can-dev

# 检查设备树配置
dmesg | grep can

# 检查硬件连接
cat /proc/interrupts | grep can

4.2 Communication Errors or Packet Loss

Diagnostic Methods:

# 检查错误统计
ip -s link show can0

# 查看错误详情
cat /proc/net/can/stats

# 检查总线状态
candump can0 -e

# 调整波特率和时序
sudo ip link set can0 type can bitrate 125000 sample-point 0.75

4.3 Network Conflict and Arbitration Issues

Solutions:

# 检查网络负载
canbusload can0@250000

# 分析消息冲突
cansniffer can0 -c

# 优化消息优先级
# 使用较低的 CAN ID 获得更高优先级

4.4 Hardware Connection Issues

Inspection Points:

  • Termination Resistor: Ensure 120Ω termination resistors at both ends of the network
  • Cable Quality: Use twisted pair cable, avoid long-distance transmission
  • Grounding: Ensure a good signal ground connection
  • Power Supply: Check the power supply of the CAN transceiver
# 测试回环模式
sudo ip link set can0 type can bitrate 250000 loopback on
cansend can0 123#DEADBEEF
candump can0