Hi we recently had a case here where one member of a CAN bus couldn't receive frames with data content of only zeros: $ cansend can0 123#0000000000000000 After some investigation we found the root cause to be a slight difference (about 1%) in actual bitrates of the two members. The one with showed the RX errors had a sjw value of 1 and a lot of time quanta (40) due to the 40MHz CAN clock. This leads to a build up of phase error (as sjw is not able to compensate for enough of the bitrate difference) which at some point leads to a framing error due to missing a stuff bit. Playing around with the sample point can improve or worsen the behavior. We can fix this quite easily by specifying a higher sjw value. Question is now: Wouldn't it make sense to increase sjw in can_calc_bittiming() to something like 5% of the total time quanta? This may increase the reliability of the CAN network when there are differences in the bitrates of the single members. Are there any arguments against such an arbitrary selection of sjw? If you agree with such a change I can come up with a proper patch. If I wrote totally nonsense please tell me :-) Regards Matthias
