Difference between revisions of "CAN bus"

Enable CAN

• Enable required modules (not persistent):

sudo modprobe can
sudo modprobe mcp251x

• Check if drivers iniatialized properly using lsmod | grep can and dmesg | grep can. Results should be:

$ lsmod | grep can
can                    46600  0
can_dev                13528  1 mcp251x

$ dmesg | grep can
[   13.950602] mcp251x spi0.0 can0: MCP2515 successfully initialized.
[  120.394646] can: controller area network core (rev 20120528 abi 9)

• To turn on the can0 interface:

sudo ip link set can0 type can bitrate 1000000
sudo ip link set can0 up

• Check that the interrupt got enabled using sudo cat /proc/interrupts | grep mcp (interrupt does not show up until the link is up):

$ sudo cat /proc/interrupts | grep mcp
133:          2          0          0          0      GPIO  34 Edge      mcp251x

Loopback test

• Loopback mode allows to test if CAN is working properly. To enable it:

sudo ip link set can0 down
sudo ip link set can0 type can loopback on
sudo ip link set can0 type can bitrate 1000000
sudo ip link set can0 up

• Two terminals are required to test:
  • First terminal:

  cansend can0 001#1122334455667788

  • Second terminal:

  candump can0

• If the loopback test is successful, it should show:

candump can0
can0  001   [8]  11 22 33 44 55 66 77 88
can0  001   [8]  11 22 33 44 55 66 77 88

• Turn off the loopback:

sudo ip link set can0 down
sudo ip link set can0 type can loopback off
sudo ip link set can0 type can bitrate 1000000

Send and receive data

• To receive data:

candump can0

• To send single frame:

cansend can0 001#1122334455667788

• To send extended frame (used by ArduPilot):

cansend can0 00100000#1122334455667788