Error frames: which node sent the message
When error frames occur in a bus, 2 questions come up:
- Which node destroyed the message by sending an error frame?
- Which node sent the message that was later destroyed?
The first question is not easy to answer because every node in a bus can be the sender of the error frame. It will look alike every time. By measuring at different places on the bus and temporarily disconnect one node after the other is the only way to find that problem.
To answer the second question, we have a fair chance to answer it with CBT2.
Using the online trigger measurement, you can show the last flawed message within the oscilloscope display. Therefore you should trigger error frames only (deselect the other triggers on the left side).
Now start a single measurement, the tester stops at the next error frame. The last message is now displayed in the oscilloscope display. You have a good chance that the error frame came after the arbitration, so you can read the node’s ID that sent the message. The screenshot is ID 702 (the green marked area of the oscillogram is the ID).