connect plc using modbus with labview

[nadeemalikpda]

hi

i m using Modbus to communicate plc with labview . but it is not working.......?

can any one give me the example program so that i can understand how to communicate ?

[MorganS]

Hi Nadeemalikpda,

Are you using the Modbus Library (http://zone.ni.com/devzone/cda/epd/p/id/4756) or the DSC Module for the Modbus communication?  There are examples included for each.

For the Modbus Library, the examples are in the .llb (MB Serial Example Master.vi, MB Ethernet Example Master.vi).

For the DSC Module, take a look at the help file here, which also has the locations of the example programs: http://zone.ni.com/reference/en-XX/help/371618F-01/lvmve/dsc_modbus_using/.

Morgan S

Applications Engineer

National Instruments

[nadeemalikpda]

i work hard on MODbus about one week but it was not fruitful for me.

Now i m using OPC Server to connect it to Mitsubishi FX  plc .Opc Server works well.

now tell me can i connect delta DVP14ss plc with opc server. ?????????

[Greg_S-Video]

Hello nadeemalikpda

I'd like to be able to help you on this issue.  Could you please descrive your application in detail?  The more I know about your issue, the better I will be able to assist you.

Thank you very much for your support of National Instruments.

Greg S.

[nadeemalikpda]

thanks for ur reply

i m using Delta plc  . i want to connect it to my labview using modbus. i use the labview MODbus Library but it is not connecting........?

Plz help me

[MorganS]

Hi,

Could you please provide more detail about how you're attempting to connect to the PLC?  Are you using one of the example VI's for the Modbus Library?  Are you getting any errors back?  Also, you mentioned that you are using the OPC Servers to communicate with another PLC - do you have the DSC Module available?  If so, you can set up an I/O Server for Modbus and simply bind shared variables to the addresses you want to read & write.

Morgan S

Applications Engineer

National Instruments

[unclebump]

are you using a serial port or an ethernet port? there are examples of both on this forum already.

[nadeemalikpda]

well i m using DVP14SS PLC trying to cneect ti to labview.i m using  a serial cable to connect it.

i use MODbus lib example which i download from ni.com

[unclebump]

See this thread for an llb file that should work.

http://forums.ni.com/t5/LabVIEW/bytes-at-serial-port-problem/m-p/271579?requireLogin=False

Your comm port settings must match between the plc comm port and labview. The serial port cable pinouts need to be checked. Can you talk to the plc with the programming software? Are you using labview on the same computer as the plc programming software? If so, make sure the programming software does not have the port locked while trying to run the labview code.

[nadeemalikpda]

hi

thanks 4 ur reply.

Yes my Plc can talk with the programming software.

and my serial port settting , PLC setting and my labview setting of MODbus is same but it is still not talking .