CAN Interfaces

CAN-Interface: Configuration

CAN is a network…

# ip link show
... all interfaces here ...
# ip link show can0
3: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN mode DEFAULT group default qlen 10
    link/can

# ip link set can0 type can help

# ip link set can0 type can bitrate 500000
# ip link set can0 txqueuelen 1000
# ip -detail link show can0
12: can0: <NOARP,ECHO> mtu 16 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
    link/can  promiscuity 0 allmulti 0 minmtu 0 maxmtu 0
    can state STOPPED restart-ms 0
       bitrate 500000 sample-point 0.875
       tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1 brp 6
       gs_usb: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..1024 brp_inc 1
       clock 48000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 gso_ipv4_max_size 65536 gro_ipv4_max_size 65536 parentbus usb parentdev 3-6.2.4:1.0
Same, but listen-only
# ip link set can0 bitrate 500000 listen-only on
Finally: turn on the interface
# ip link set can0 up

CAN Utils

Nice little utilities …

  • Userspace relic of the SocketCAN project (⟶ make CAN a network)

  • cansend: send a frame

  • candump: recording frames from one or more CAN interfaces

  • canplayer: replay from recording

  • … and others …

  • ⟶ testing!

Installation

Fedora
# dnf install can-utils
Debian/Ubuntu
# apt install can-utils

CAN Utils: Usage (1)

Generating frames:

$ cansend can0 123#deadbeef
$ cangen -D deadbeef -L 4 can0
$ cangen -D deadbeef -L 4 -I 42 can0
$ cangen -D i -I 42 -L 8 -g 100 -p 100 can0

Sniffing frames:

$ candump can0
$ candump can0 can1 ...

CAN Utils: Usage (2)

Record, Replay:

$ candump -L can0 > can0.log
$ canplayer < ./can0.log

Changing the interface:

$ canplayer can1=can0 < ./can0.log

vcan: Virtual CAN-Bus

Problem:

  • CAN development traditionally needs hardware

  • … at least two participants (loopback on one controller possible))

  • ⟶ programming and testing as hard as can be

Lösung:

# modprobe vcan
# ip link add dev mein-test-can type vcan
# ip link set mein-test-can up
# canplayer mein-test-can=can0 < ./can0.log

Fantasy:

  • Programming and testing on the PC

  • Continuous integration

  • …