CODEWITHSUNDEEP
csocketscan-bussocketcanrecvmsg
Wojciech Stańczuk
Wojciech Stańczuk

Reputation: 13

Confirmation that the message was sent to the CAN bus using socketCAN

I would like to confirm that my message has been saved on the CAN bus with socketCAN library. The socketCAN documentation describes this possibility when using the recvmsg() function, I have problems with its implementation.

The function I want to achieve is to confirm that my message won the arbitration process.

Upvotes: 1

Views: 1596

Answers (2)

krnk
krnk

Reputation: 11

I think you can use the command "candump can0/can1" on your PC, it will shows the CAN packet received on given CAN interface.

Usage: candump [options] <CAN interface>+
  (use CTRL-C to terminate candump)

Options: -t <type>   (timestamp: (a)bsolute/(d)elta/(z)ero/(A)bsolute w date)
         -c          (increment color mode level)
         -i          (binary output - may exceed 80 chars/line)
         -a          (enable additional ASCII output)
     -b <can>    (bridge mode - send received frames to <can>)
     -B <can>    (bridge mode - like '-b' with disabled loopback)
     -u <usecs>  (delay bridge forwarding by <usecs> microseconds)
     -l          (log CAN-frames into file. Sets '-s 2' by default)
     -L          (use log file format on stdout)
     -n <count>  (terminate after receiption of <count> CAN frames)
     -r <size>   (set socket receive buffer to <size>)

Upvotes: 0

Alexander Solovets
Alexander Solovets

Reputation: 2507

I think mentioning recvmsg(2) you refer to the following paragraph of the SocketCAN docs:

MSG_CONFIRM: set when the frame was sent via the socket it is received on.
      This flag can be interpreted as a 'transmission confirmation' when the
      CAN driver supports the echo of frames on driver level, see 3.2 and 6.2.
      In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set.

The key words here are "when the CAN driver supports the echo of frames on driver level", so you have to ensure that first. Next, you need to enable the corresponding flags. Finally, such confirmation has nothing to do with arbitration. When a frame looses arbitration, the controller tries to re-transmit it as soon as the bus becomes free.

Upvotes: 3

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