Basically, I am trying to connect a profibus slave (AB 7000C) to a gas analyzer (p5) via R485. I am able to get the AB7000c unit to share data with the profibus network however I am not seeing a data exchange on the subnetwork monitor.
I need advise on how to test the connection and validate.
The best way to troubleshoot the subnetwork (RS485 side) is to use the “Start Logging” functionality. When you run this it will provide a log of all of the traffic the communicator saw on the serial line. If you save this log and drag and drop it onto this forum post, as well as your .cfg configuration file, I can review and let you know what could be problematic.
Hello Nrainsford,
Thank you for the response. I attached both files to this message.
log.txt (36.7 KB)
when I attempt to attach the .cfg file, I am getting this error:
Sorry, the file you are trying to upload is not authorized (authorized extensions: jpg, jpeg, png, gif, txt, zip, tar).
Sorry about that, I will have to look into adding the ability to provide .cfg files here.
One thing I can immediately tell from the log though is that you are not getting any response from the device you are trying to communicate with. Can you confirm you are using Modbus RTU on the subnetwork side?
The following are reasons why you would not see a response from a Modbus RTU slave device,
-You are trying to query the wrong node. In this case you will want to double check that you have the right node selected in your configuration file. In your case this is 1 (from the log)
-There is an issue with the wiring on the serial bus. Depending on the serial interface (RS232, RS485 or RS422) you may just need a null modem or to switch the rx and tx lines.
-There is an issue with the subnetwork serial settings (baud rate, parity, stop bits and data bits).
Thanks for the prompt response.
The cfg file is available via Justbeamit at https://www.justbeamit.com/wd38q
Confirmed that the P5 (slave) device is using modbus RTU over RS485 and there is only 1 node on the subnetwork (P5).
I checked the wiring and replaced each and received similar results.
I am having issues with that link, it says “sorry, this download link no longer exists :(”
Although there is 1 node, are you sure that node is node address 1?
Are you using RS485 2-wire?
Unfortunately in almost every case it comes down to the three points I previously listed. An actual error in the configuration of the Modbus transactions would still result in an exception response rather than a timeout.
Unfortunately I get the same thing with this link. It is probably easier if you want to email the file to,
us-support@hms.se
just sent the config file
Hello,
When last we had spoken I suggested swapping the A and B lines, I hope this fixed the issue!
Nick