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CAN: Will standard length identifiers be accepted by extended identifier filters?

Question asked by Bart Kuivenhoven on Jun 20, 2019
Latest reply on Jun 21, 2019 by Alice_Yang



I've recently been put to work on a CAN message interpreter library, and the previous developers left the company without much in the way of documentation.


It seems as if the library is written with the assumption that the customer should always just set their driver to accept extended length id's and that when a standard length identifier hits the extended length filter, it will pass through anyway so long as the value is correct. I'm now trying to see if this assumption is correct for the LPCXpresso 1769.


I've looked at the datasheet, and it says there's basically a list of filters, numerically sorted, with a bunch of pointers to the list indicating where each of the segments of the list starts. That way a message first gets passed through the standard filters first and then hits the extended filters if it doesn't match.


So the question now is, with the numeric value of the ID being correct, can it only be accepted by a standard length filter, or can it also be accepted by an extended length filter?



- Bart