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communication port redundancy!

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elecfan

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I am using the following config in order to improve the reliability of my system.
two redundant micros are used, where each one provides two CAN based data port.

in the right, three computers are receiving data through a concentrator, which received the data from micros, compares them and sends them to computers, if both are the same.

please share you experience on similar projects,
what would be the best design to keep the system and reliable.

redundant config.jpg


Best regards
 

I'm confused. You've got 4 ports, bit then you say 'if both are the same'. What do you mean? Further, you've got the problem of two messages not necessarily arriving at the same time. How d you handle that? I'm not sure I even see the necessity of this method. If you use a robust error correction method, e.g. CRC, won't that be adequate?
 

CAN has built in CRC for error detection (not correction) for the packets. It also supports acknowledgement messages so senders can determine if the packet was received by someone.

If the point is to have redundancy in case someone takes a pair of dikes (diagonal cutters) and cuts the cable, then just keep track of the messages that arrive on either bus and throw away duplicates.
 

for the board at the left, I am considering two boards (master and slave).
for each board (i.e. microcontroller), two CAN ports, one of them goes to BUS A and the other one to BUS B.
For the right side, I did a mistake in drawing. there should be one connection from each BUS to the computers. not more.

CRC should handle (detect) the errors to some stage. but in safety critical applications, usually a duplicated CAN port is recommended.
But can the synchronization of the ports be an issue?

what is the reliability of the CAN protocol itself?

In literature of the subject, time redundancy is also recommended. meaning that sending each packet of data at least for three times, and apply voting on them in the receiver side!

any experience on this?

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this is also important. but I assume the main idea in using different types of redundancy (both hardware, information and time) can aldo be handling the problems in noisy environments.
 

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