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MSPM0G3519: Two node with same node id and both nodes sending PDO's with same data

Prajesh Karmalkar
Prodigy 140 points

Part Number: MSPM0G3519

Hi TI,

We have a CAN-based system with one master and several slave nodes.
, we connected two nodes with the same Node ID, and both nodes also respond with same SDO data.

In this case, our master is supposed to detect the duplicate nodes and take the necessary decision.

However, we are facing an issue:

When both nodes try to send an SDO response frame to the master's request at the same time, we can see only one SDO frame on the CAN bus (sniffer log).
The second node’s response is never visible.

Can you please explain why only one frame is observed on the bus even though two nodes are responding?

 

For referance: image.png

 

Expected to get :

image.png

 

  • 0
    TI__Genius 11995 points

    Hi Prajesh,

    Do you have MSPM0 working as CAN "master" or "slave"?

    From your description, you only see one slave response frame in CAN BUS right? So the problem is that you could not observe desired two slave response frame in BUS.

    One of my guess is that two slave nodes have a totally same ID and data content, if they response the CAN master message at a same time, it may show only one frame in the bus.

    I recommend to do below test:

    • Set two slave nodes with different ID, to check whether the slave nodes itself works well.
    • Set two slave nodes with same ID, and add a small delay for one of the slave node. Then observe the bus waveform.
  • 0 in reply to Pengfei Xie
    Prodigy 140 points

    - Set two slave nodes with different ID, to check whether the slave nodes itself works well.

    with different slave ids the slave nodes works well.

    - Set two slave nodes with the same ID, and add a small delay for one of the slave nodes. Then observe the bus waveform.

    By adding a small delay in one of the slave node, it works as expected, showing both node data with the same ID as shown in the second image.

  • 0 in reply to Prajesh Karmalkar
    Prodigy 140 points

    Also, one thing i noticed is that when we do a slight change in the data of the SDO subindex in one board and keep the other board data unchanged 

    Then, only the specific subindex data is shown, with both nodes having the same IDs.

    As you can see in the image below, the last 4th subindex reply from both the same ID nodes.

  • 0 in reply to Prajesh Karmalkar
    TI__Genius 11995 points

    Hi Prajesh,

    Could you check whether the shown data is the node data which is smaller in value?

    I think it may caused by that both nodes has responded to the CAN master. And in previous test, as they have the exactly same content, so only one message is observed in the bus.