Controller Area Network : Read back the sent CAN frame using the same transceiver and send it to ASW

Discussion in 'Embedded Systems and Microcontrollers' started by Kavimani Ramaraj, Feb 7, 2016.

  1. Kavimani Ramaraj

    Thread Starter New Member

    Feb 7, 2016
    Hello All,

    My requirement is to read back the sent CAN frames using the same CAN transceiver and send it to Application software.

    1) In principle, is it possible to send and receive the same CAN Frame using same CAN transceiver simultaneously? (I think CAN transceiver does bit arbitration in this manner)

    2) Is it possible to configure a CAN frame as "Send" and "Receive" for the same CAN Node? Does it not throw any configuration error?

    Many thanks in advance for your support!
  2. Papabravo


    Feb 24, 2006
    1) You must distinguish between the controller and the transceiver. In most networks with reasonable cable distances they are separate parts. CAN controllers always monitor the bus during transmission to detect bit errors. What they do not do is fill up a receive message buffer with the receive data. You can return the transmit data if you can determine that it was sent correctly. The transmitter verified it bit by bit assuming it won arbitration and no other node threw an error frame. The transceiver allows it, but the controller does not, at least not the way you want it to.

    2) At the physical and MAC layers CAN knows nothing about node identity. Messages have an identifier field which may contain, but is not required to contain, a node address. The only sensible network rule to enforce is that "two nodes may not transmit a message with the same identifier". This is obvious because it would defeat the arbitration mechanism. In network terms only one node can produce a message with a given identifier; zero, one, or more nodes can consume that message. All nodes that receive the message correctly, are required to ACK the message, regardless of whether they consume it or not. Nodes cannot consume their own messages.
    Kavimani Ramaraj likes this.