CI867 Card I am, I am placing the Modbus TCP slaves in the tree, but I have trouble reading them
CI867 Card I am, I am placing the Modbus TCP slaves in the tree, but I have trouble reading them, communication is lost. Add in the configuration of the Master in diagnostics Poll Time 2000 ms, resulting in communication was maintained, but now I mark an alarm of "Polling retrieval error", the only way to avoid this mistake is placing spare among the slaves, but this unused nodes involves me, I can help solve this problem, I attached pics of settings.
Voted best answer
Remove the "spare" remote units. They are not fixing anything and only make the problem harder to find.
When you poll a remote slave that is broken ( or not there ) then you may introduce a delay into the whole network. Since it sounds like you have a problem getting slaves to respond, adding more delays is not fixing the problem , it is hiding it.
Polling is only usefull when you are not otherwise talking to the remote node, and 2 seconds seems very fast. You should try to increase the polling time as much as possible.
Go back to using only 1 slave and get that working. Then add more slaves until you identify where the problem is. Try to identify if you have a programming problem, a cable problem or something else. I have seen "home-made" ethernet cables cause serious problems when the wrong pairs were used. The cable appears OK when you point-to-point test, but the twisted pairs did not protect against interference properly.
You may use WireShark to monitor and analyze what goes on in your network.
It's a very hany software to use when having communication issues.
It can be downloaded from www.wireshark.org
Connect it to your ModbusTCP network, via a hub or a managed switch with port mirroring. Or install it on the Modbus slave, if possible.
Regarding your lost communication, you can see if one of the Modbus units are
terminating the connection, with a RST/FIN TCP message.