rt with modbus serial

[LavUser]

He All!!!

I want to configure Modbus, but for that I need to create a Server I/O or something lake that. I am working with LabVIEW 8.0.1, a Real Time and a PXI-8421/4. So, there is a manual to do that or who could help me?

LavUser

[Khalid]

Hi,

What Modbus device will you be connecting to?  Where will you be connecting from?  RT?  PC? 

Regards,

-Khalid

[LavUser]

 Hi Khalid!!!

I really begin with LabVIEW and I need to see a signals, they will see on Modbus. I am working with a PXI-8145 RT where is too a PXI-8421/4 RS-485. I have tested the serial communication and it is working, but now the question is: where will I define the master? and what to do I need? Maybe a driver? I found a library for Modbus, but is not clear what next...!!!

That was what I found:

There is a Modbus library for LabVIEW 7.1 available from our website:
&nbsp;<a href="http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=F158..."

In advance thanks very much and I will be glad, hear somethig about that.

Yaridia

[AlexxxR]

Hi,

I think this link might be very helpful for you:

http://digital.ni.com/public.nsf/websearch/2CD034F223C650E9862569570041995C?OpenDocument

Greetings Alex

NI Switzerland

[Khalid]

Yaridia,

So, you have a PXI controller with a RS-485 board.  That's good.  I am assuming you want to connect to Modbus devices using this 485 card?  If yes, then what kind of devices are these?  Are they PLCs?  RTUs?  Or just Instruments that use the Modbus communication protocol? 

In each case, you will use the NI Modbus library and connect to the devices.  Start by testing this on your desktop PC using one PLC/device at a time.  There's a Modbus Serial Master in the library that is a good place to start.  You don't need the Ethernet version since you appear to be using RS-485.  So, once you get a simple setup working, you can move this to the RT.  Note that you will not be able to test multiple devices from your desktop PC (unless you have a 485 card in the PC as well).  So, test one device at a time on the PC.  Then test the same on RT-PXI.  And finally put everything together on RT-PXI, i.e., use multiple devices (multi-drop off the RS-485 network). 

Also, you should address the Modbus devices uniquely (between 1-32).  Your PC / RT is the Modbus Master. 

Hope this helps.  Let us know if you run into any issues.

Regards,

-Khalid

PS:  I am guessing you have other PXI cards for other high-speed/deterministic things too... using the RT-PXI just to talk to a Modbus network seems a little stretch, IMHO.

[unclebump]

Modbus is a master/slave communication setup. The master device requests data from a slave device, or writes data to a slave device. The master can be a plc, opc server program, hmi display, computer, labview... The slave device can be another plc, labview program, opc server, some type of instrumentation meter, variable freq. drives...

Try this document.

[LavUser]

Hi Khalid!!!

As device sind particular card, it means, the company where I am working had it developed. And as soon as I test, I I will tell you, because today it is not possible. Thanks very much for your help.

Have a great day!!!

Yaridia

[LavUser]

Hello Khalid!!!

Today I had tested the communication but it is not working. So I tried to test the communication between a computer and a 4 serial car, the car is on the computer. So, what can I do?

Kind Regards

Yaridia

[Khalid]

Hello,

So, these "cards" speak the Modbus protocol?  And they are plug-in cards installed in a computer?  And you want to communicate to these using the 485 card in your PXI?  Did I get the setup right? 

Thanks,

-Khalid

[LavUser]

Khalid!!!

It is working, now I must to configurate a VI where I could select the poll and the parameters for Modbus.

Thanks very much!!!

Have a great day!!!

Yaridia