CAN Bus Communication: Same Bit Rate, Different Time Segments

Kyle Muehlegg 0
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I would like to preface that I am new to CAN, so I apologize if this is an obvious question.

I am using an STM32 microprocessor that has CAN communication, whose bit rate I have set to 500 kBit/s. I am trying to communicate with another node (whose source code I do not have access to) and their bit rates are the same (500 kBit/s). I am wondering if they're using the same bit rate but different bit time parameters (Prescaler, SyncJumpWidth, TimeSeg1, TimeSeg2), will they still be able to communicate with each other?

can-bus
1 Answers

Possibly, but it isn't certain. Propagation delay caused by long wires for example, will make it more or less critical where the sample point is located. Stubs or poorly terminated buses may suffer from signal reflections that make the sample point location more or less critical. Higher baudrate leads to more bit length inaccuracies. As does a poor clock source. And so on. Also if you go with some strange and exotic settings, nothing tends to work but you get error frames.

I have good experience from following the requirements of the CANopen standard, which is to place the sample point as close to 87.5% as possible. The easiest way to achieve that is by a total of 16tq where phase seg2 is 2tq long. 16 tends to work well with most prescaler clocks as well. Note that there's a hard requirement by the CAN standard not to use more than 25tq.

Lundin0
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