CRIO ModbusTCP Server with Modbus Library

[vrana]

Hello,

I am to deploy Modbus Server (Slave) on CRIO 9073 using Modbus Library. Application on another PC, written in C#, is used to read holding registers (which are, in turn, filled with data acquired from RTD modules). The server was tested successfully on my PC, application was able to read holding registers. Also, the server was made by recycling the "MB Modbus Slave Example.vi". Example vi runs another vi (Modbus Ethernet Demon), and it was all right because both were on the same machine. When deployed on CRIO, the server won't run because it cannot find Demon vi. And now, the question: how to deploy both Server and Demon vi on CRIO?

[Maciej_Antonik]

Hi

The example you are using runs the Demon using VI Server call. So you need to copy this Demon VI onto the target manually and put it into appropriate directory there (see how path to it is consteucted in the example). 

Did you have a look at some examples available?

http://zone.ni.com/devzone/cda/epd/p/id/6166 (uses serial communication)

http://zone.ni.com/devzone/cda/epd/p/id/5642 (TCP communication)

Regards

[vrana]

Thank you for reply, Maciej. Your proposal makes sense, indeed. However, I am not quite sure how I am supposed to copy the demon vi on the target manually. Is it possible for you to give me instructions step-by-step? Thank you again for your help.

[Maciej_Antonik]

Hi

This tutorial should be helpful: http://digital.ni.com/public.nsf/allkb/571113C2CE05998E862574E8006005A2

Then if you don't know how all those 'strip path' VIs work, start with deleting them and just adding a constant path name instead. The path name you are giving is the one where you've transferred your VIs to. 

Hope it helps

[vrana]

Thanks again, Maciej, your link was very helpful. However ( 🙂 ) another problem has arisen. Demon vi have to be compiled for VxWorks that runs on cRIO. How should I do that?

Best regards 

[Dusan_Vukasinovic]

Hello guys,

here is solution for all your problems. I have attached VI that does what you need. Please test it, and let me know if you need any additional help.

Best regards,

Dusan Vukasinovic

[Maciej_Antonik]

Thanks Dusan!

Vrana - my apologies - the reason for your problems I gave you  was correct, but the solution wasn't. Thanks again Dusan for clarifying.

[vrana]

Modbus problem is solved! Dusan, thank you very much for all your efforts! INT crew is forever in your debt!

The problem was with cRIO 9073, definitely. The same program runs without any problems on cRIO 9074.

Perhaps it should be said that cRIO and PC were connected with crossed ethernet cable, "p2p".

We were unable, however, to determine the exact cause of error (hardware or firmware).

The problem was persistent with cRIO 9073, and nonexistent with cRIO 9074.

Once again, thankyou, Dusan, for your time and effort. Know that it is very appreciated 🙂

Don't forget to visit us next time you are in Belgrade!