Node stops sending messages, when other nodes get plugged in.

[JannikSteiner]

Hello everyone,

I am currently having the Problem, that I need to implement a ECU, that is sending a CAN Message, containing the state of different buttons.
We have been using this MCU (STM32f746g) for months now and have never had any problems when it was only listening to messages.

Now that it has to send something, we are getting the following problems:

On my labbench, everything works fine, the message is sent. Even with a busload of >90%, the message is beeing sent without a problem.
As soon as I plug it into the Car, Tx is stopping. The rest of the CANBus still keeps on working. I can also still receive messages on the described MCU.
The car intern CANBus has a load between 30% and 50%, so busload can´t be the problem here.

I tried unpugging all nodes from the CAR and plugging them back in one at a time to see which one causes the problem, and I got mixed results. Sometimes the Tx stops if I plug in a node with a long cable, sometimes when I plug one in that sits right next to it, so I cannot see any patterns.

The Bus has one termination resistor too much (one Node in the middle has it hardwired in), bringing the total resistance between CANH & CANL down to 40Ohms, but since all the other Nodes keep working without trouble, I think this is not the problem.

Do you have any recommendations on what to check?

Thank you!

[M.Heidemann]

Dear Jannik,

This forum is only for PEAK related support requests, not general CAN-questions, so
is this request related to a specific PEAK-Hardware?

As soon as I plug it into the Car, Tx is stopping

Have you checked if all nodes use the exact same bitrate yet?

Best Regards

Marvin

[JannikSteiner]

Hello Marvin,

Im sorry, I thought, this is a forum generally about CANBus,
But yes I am using the PCAN USB CAN-FD Dongle to monitor the traffic. But I think the Problem is not coming from the Peak device.

All the other Nodes are using the same bitrate (As I said, the Bus keeps working, just the one node stops the Tx.


Best regards
Jannik Steiner

[M.Heidemann]

Hi,

you could use your PCAN-USB FD to check the traffic on the bus.

In PCAN-View check the Trace Menu and enable all optional frames (Stauts-frames, error-frames, etc) and run a trace. Share your trace with us, maybe we can identify the issue based on your trace.

Best Regards

Marvin