09 CAN

1 CAN Bus Overview

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

1.1 CAN Bus Technical Specifications

ParameterSpecification
Protocol StandardISO 11898-1 (CAN 2.0A/2.0B)
Interface Quantity2 independent CAN interfaces
Transmission MediumTwisted pair
Network TopologyBus type
Transmission DistanceMax 1000 meters (5Kbps)
Max Node Count110 nodes
Data Frame Length0-8 bytes
Arbitration MechanismNon-destructive bitwise 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
  • Real-time: Deterministic message transmission delay
  • High Reliability: Differential signal transmission, strong anti-interference ability

Application Fields

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

2 GM-3568JHF CAN Interface Configuration

According to product specifications, GM-3568JHF development board provides 2 CAN interfaces to meet various industrial application needs.

2.1 CAN Hardware Connection

CAN wiring between 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 for testing. Connect the H terminal and L terminal of the two devices.

CAN_2

Check Interface

Check if 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 Setting

Set the baud rate on the development board and test (take CAN0 as a test sample this time)

# Turn off CAN0 interface
sudo ip link set can0 down
# Set bit rate to 250000
sudo ip link set can0 type can bitrate 250000
# Turn on CAN0 interface
sudo ip link set can0 up

# Send (Standard frame, data frame, ID:7ff, data:11223344556677)
cansend can0 -i 0x7ff 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88

# Receive
candump can0

Test Results

  • Development Board Test Result:
CAN_3
  • CAN Analyzer Test Effect:
CAN_4

3 CAN Network Diagnosis and Debugging

3.1 Using cansniffer for Network Analysis

# Install cansniffer
sudo apt-get install can-utils

# Start network sniffing
cansniffer can0

# Sniffing with filter
cansniffer can0 -c 0x100-0x200

# Save log
candump can0 -L > can_log.txt

3.2 Network Load Test

# Generate test traffic
cangen can0 -g 10 -I 123 -L 8

# Test network bandwidth
canbusload can0@250000

# Stress test
for i in {1..1000}; do
    cansend can0 123#DEADBEEF
done

4 Troubleshooting

4.1 CAN Interface Cannot Start

Check Steps:

# Check kernel modules
lsmod | grep can

# Manually load CAN modules
sudo modprobe can
sudo modprobe can-raw
sudo modprobe can-dev

# Check device tree configuration
dmesg | grep can

# Check hardware connection
cat /proc/interrupts | grep can

4.2 Communication Error or Packet Loss

Diagnosis Method:

# Check error statistics
ip -s link show can0

# View error details
cat /proc/net/can/stats

# Check bus status
candump can0 -e

# Adjust baud rate and timing
sudo ip link set can0 type can bitrate 125000 sample-point 0.75

4.3 Network Conflict and Arbitration Issues

Solution:

# Check network load
canbusload can0@250000

# Analyze message conflict
cansniffer can0 -c

# Optimize message priority
# Use lower CAN ID to get higher priority

4.4 Hardware Connection Issues

Check Points:

  • Terminal Resistor: Ensure there are 120Ω terminal resistors at both ends of the network
  • Cable Quality: Use twisted pair to avoid long distance transmission
  • Grounding: Ensure good signal ground connection
  • Power Supply: Check CAN transceiver power supply
# Test loopback mode
sudo ip link set can0 type can bitrate 250000 loopback on
cansend can0 123#DEADBEEF
candump can0