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CAN Interface

CANBUS Introduction

A controller area network (CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles to save on copper, but it can also be used in many other contexts. For each device, the data in a frame is transmitted serially but in such a way that if more than one device transmits at the same time, the highest priority device can continue while the others back off. Frames are received by all devices, including by the transmitting device.

Preparation​

  • two Radxa development boards with CANBUS
  • two CANBUS modules

Enable Overlay​

Please refer to Device Tree Configuration to enable CANBUS-related Overlay, eg: "Enable CAN1-M0"。

Connection​

master            CAN module          CAN module         主设备
3.3V     <-->     VCC                 VCC      <-->      VCC
GND      <-->     GND                 GND      <-->      GND
CAN_TX   <-->     CTX                 CTX      <-->      CAN_TX
CAN_RX   <-->     CRX                 CRX      <-->      CAN_RX
                  CANH      <-->      CANH
                  CANL      <-->      CANL

Installation of test tools​

sudo apt update
sudo apt-get install can-utils iproute2

Check CAN node​

$ ip a
can0: flags=193<UP,RUNNING,NOARP>  mtu 72
       unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
       RX packets 144  bytes 1152 (1.1 KiB)
       RX errors 175  dropped 0  overruns 0  frame 35
       TX packets 0  bytes 0 (0.0 B)
       TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
       device interrupt 62

Loopback test​

One board acts as the transmitter and the other as the receiver

  • sending end
$ sudo ip link set can0 down
$ sudo ip link set can0 type can bitrate 1000000 dbitrate 1000000 loopback on fd on
$ sudo ip link set can0 up
$ sudo cansend can0 123#11223344
  • receiving end
$ sudo ip link set can0 down
$ sudo ip link set can0 type can bitrate 1000000 dbitrate 1000000 loopback on fd on
$ sudo ip link set can0 up
$ sudo candump can0
can0  123   [4]  11 22 33 44

Development Reference​