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Message Delays on CAN Bus with High Bus Traffic

Primary Software: Driver Software>>NI-CAN
Primary Software Version: 2.3.2
Primary Software Fixed Version: N/A
Secondary Software: N/A
Hardware: Industrial Communications>>CAN

Problem:
When the CAN bus traffic is low, my messages transmit perfectly, but when the bus traffic becomes high, I start seeing delays. Why is this happening?

Solution:
It is possible that the arriving messages have a lower ID than the outgoing messages. In this case, the Controller will handle the lower IDs (incoming) first, which can cause delays for outgoing messages, because only one message can be on the bus at a time. You can try to set filters to block the incoming traffic before it arrives to the controller. There are shipping examples for setting filters located in the LabVIEW Example Finder and in the NI-CAN directory. These examples show how to use the on-board filters.

Related Links:
KnowledgeBase 3JL8MLFM: How Can I Monitor the NI-CAN Bus?
KnowledgeBase 3W3B7I5N: Why am I Unable to See Any Traffic On the CAN Bus When I Use the PCMCIA-CAN

Attachments:





Report Date: 05/06/2006
Last Updated: 07/07/2006
Document ID: 3X59Q4C5

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