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+--- Thread: Modbus Master Scanner (/showthread.php?tid=3208)
Modbus Master Scanner - sjfp - 08.03.2021
Been creating a LM APP for testing Modbus networks on our clients sites, so we have a working model that can poll Modbus address's and get the values from particular registers we need, and can be used as a Modbus slave to simulate an Virtual Modbus Meter.
Next step is now to find is it possible to use LM to scan the Modbus network to see what the systems Modbus Master is actually requesting data for.
Looking to test whether Modbus Master is asking for the correct data from the meters, like all the address's and what registers.
Need to make sure the Modbus Master has been setup correctly and is working getting by reading all meter address's are being requested.
The Modbus Master has been setup by others and we have no means to test config, hence this app.
Any help in getting a sample script would be appreciated
Thanks all.
RE: Modbus Master Scanner - admin - 09.03.2021
Do you mean that you want to capture Modbus TCP communication between other master and slave devices? It's not possible to do this directly. One solution is to temporarily disconnect one of slaves and place LM with the same IP as the slave instead. Another solution is to use Wireshark for capturing but for this you will either need a PC with two network interfaces so all traffic goes through it or you need an Ethernet hub (not a switch) which passes all traffic to all ports.
RE: Modbus Master Scanner - sjfp - 09.03.2021
(09.03.2021, 06:49)admin Wrote: Do you mean that you want to capture Modbus TCP communication between other master and slave devices? It's not possible to do this directly. One solution is to temporarily disconnect one of slaves and place LM with the same IP as the slave instead. Another solution is to use Wireshark for capturing but for this you will either need a PC with two network interfaces so all traffic goes through it or you need an Ethernet hub (not a switch) which passes all traffic to all ports.
Thank you for your response, yes we want to see the traffic between master and slave's
Sorry I forgot to include we are using the RS485 ports to interact with Modbus, not TCP
So we Have Port 1 as Polling and Port 2 as Slave.
Does this make a difference on being able to pass the traffic through the LM and incept the messaging.
RE: Modbus Master Scanner - admin - 09.03.2021
With RS485 you can simply connect LM to the same bus and receive all data as is.
RE: Modbus Master Scanner - sjfp - 09.03.2021
(09.03.2021, 07:43)admin Wrote: With RS485 you can simply connect LM to the same bus and receive all data as is.
Thanks again, but the question now is how to do that. and what the best way to show all the potential data passing through.
Was thinking of something like using a frame to display data.
Not sure how to achieve this though