Thank you very much for your detailed feedback.
Actually the mask feature with the beep function I already used, however I wanted the scope to beep when a faulty bus frame is received by in the buffer table below.
However thinking about it, if there is a frame fault, then in general we can say there will also be a mask fail (unless the frame is outside the edges of the display).
Localising a loose contact with this method is very useful, and much better than serial diagnosis. I did a simulation yesterday on a C-Class and it worked perfectly. I havnt yet had success with localizing the area of the bus fault by the frame ID, mainly because the entire bus is disturbed.
In my head I assumed that only a short circuit would disturb the entire bus and that a loose CAN connection at a control unit would not disturb the bus, but actually the bus is quite noticeably disturbed when there is a loose contact. I see a saw-tooth pattern during the time of the fault. Therefore we can say that using this ChA + B mask is useful in locating pretty much all wiring faults associated with a CAN bus. And its super easy to setup. From the saved mask fails we can determine the type of fault - short to positive/ground, loose contact etc.
I noticed also that you need quite a high sampling rate to reduce the quantity of "misread" frames (which could be interpreted as a fault on the bus), this is probably mostly influenced by the probes I am using so I might try this in future with 60Mhz probes instead. Also nice that the scope suggests to use a higher sampling rate.
Thanks for your help!
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