Error frames: which node sent the message

When error frames occur in a bus, 2 ques­ti­ons come up:

1. Which node des­troy­ed the mes­sa­ge by sen­ding an error frame?
2. 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).