4.7 CAN Bus Test

This example demonstrates how to use Linux APIs to send and receive data from CAN bus, please refer to the source code for detail.

Hardware Preparation:

  • Two MYD-C437X-PRU development boards
  • Two data cables to connect J10 of the two boards: CANH<->CANH，CANL<->CANL，GND<->GND
  • Two USB to TTL converters, each connects J25 of MYD-C437X-PRU development board and a USB host of PC respectively, set the baudrate of serial port on host PC to 115200-8-n-1

Software Preparation:

  • Linux Kernel 4.1.18
  • can_test application
  • ip link applicatoin
  • can_utils tools built with Buildroot

Test Steps:

  • Copy cross compiled <WORKDIR>/Examples/can/can_test to /usr/bin directory of the MYD-C437X-PRU development board, run can_test application as below:
# can_test --help
Usage: can_test [options]

Version 1.0
Options:
-d | --device name   can device name: can0
-b | --baudrate baudrate   set baudrate, default baudrate:50000
-l | --loop              operate circularly, default not operate circularly!
-w | --write  frame     frame string with format ID#MESSAGE. such as: 123#112233445566
-h | --help                Print this message
  • Set the baudrate for can interface as below: 
# ip link set can0 down
# ip link set can0 type can bitrate 50000 triple-sampling on
# ip link set can0 up
  • The previous processes are no need to be executed manually. During running can_test, it will be set automatically.
    One board is used as sender, the other is used as receiver, they communicate with can_test application as below: 
# chmod 777 /usr/bin/can_test
# can_test -d can0 -w 123#112233445566
[ 6862.997962] c_can_platform 481cc000.can can0: setting BTR=1c1d BRPE=0000
====== write  frame: ======
 frame_id = 0x123
 frame_len = 6
 frame_data = 0x11 0x22 0x33 0x44 0x55 0x66
===========================
  • Execute the following command at other board to receive data as below: 
# chmod 777 /usr/bin/can_test
# can_test -d can0 -l
[ 6484.014811] c_can_platform 481cc000.can can0: setting BTR=1c1d BRPE=0000
  can0  0x123  [6]  0x11 0x22 0x33 0x44 0x55 0x66

Note: -l option is used for operating circularly. Note: In case of the following error, please modify the value of "tx_queue_len" as below: 

# can_test -d can0 -w 123#112233445566
  can raw socket write: No buffer space available

# echo 1000 > /sys/class/net/can0/tx_queue_len
  • Exchange roles of the two boards, the result is the same.