Controller Area Network (CAN)

All MX-4 boards are equipped with CAN controllers. The SocketCAN application interfaces is used to access hardware, this is the standard interface now days to communicate with CAN hardware on Linux.

Configuration

The most common way to configure a CAN device is using the iproute2i util.

List of supported switches:

$ ip link set can0 type can help
Usage: ip link set DEVICE type can
        [ bitrate BITRATE [ sample-point SAMPLE-POINT] ] |
        [ tq TQ prop-seg PROP_SEG phase-seg1 PHASE-SEG1
          phase-seg2 PHASE-SEG2 [ sjw SJW ] ]

        [ dbitrate BITRATE [ dsample-point SAMPLE-POINT] ] |
        [ dtq TQ dprop-seg PROP_SEG dphase-seg1 PHASE-SEG1
          dphase-seg2 PHASE-SEG2 [ dsjw SJW ] ]

        [ loopback { on | off } ]
        [ listen-only { on | off } ]
        [ triple-sampling { on | off } ]
        [ one-shot { on | off } ]
        [ berr-reporting { on | off } ]
        [ fd { on | off } ]
        [ fd-non-iso { on | off } ]
        [ presume-ack { on | off } ]

        [ restart-ms TIME-MS ]
        [ restart ]

        Where: BITRATE  := { 1..1000000 }
                  SAMPLE-POINT  := { 0.000..0.999 }
                  TQ            := { NUMBER }
                  PROP-SEG      := { 1..8 }
                  PHASE-SEG1    := { 1..8 }
                  PHASE-SEG2    := { 1..8 }
                  SJW           := { 1..4 }
                  RESTART-MS    := { 0 | NUMBER }

So to simply configure bitrate of one specific CAN controller:

$ ifconfig can0 down
$ ip link set can0 type can bitrate 250000
$ ifconfig can0 up

To query a device for its current configuration:

$ ip -d link show can0

To query a device for statistics:

$ ip -s link show can0

Utilities

You should also get familiar with can-utils. This is a colllection of tools that are great to debug CAN networks, applications and should be used as a source of insperation if you are to write your own application that interacts with an CAN network.

Dump all incoming data:

$ candump -l any,0:0,#FFFFFFFF    (log error frames and also all data frames)

Send a single CAN frame:

$ cansend can0 123#DEADBEEF