Does anyone have examples of sending Modbus commands in LW/CVI?

[Kirk45]

I am trying to communicate with a Watlow temperature controller through LW/CVI using Modbus protocol. Does anyone have any tips or sample code where they have had success with this before?

[RobertoBozzolo]

In case your instrument is connected via RS232, here you can find an answer I posted to a similar question some time ago. The manual linked includes some examples of communication for C language that can be incorporated in
CVI with little adaptations.

[Kirk45]

Unfortunately, I am connecting via 485. Can you help with this?

[AllanS]

Kirk,

I am struggling somewhat to locate information on modbus in CVI but i did however find this thread...

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=50650000000800000093170000&ECategory=LabWindows%2FCVI

Does any of this information pertain to you?? If it does not let me know and I will continue researching!! Have a great day!

Allan S.
Applications Engineer
National Instruemnts

[RobertoBozzolo]

RS485 should act the same as RS232: command syntax remains the same and only input/output of messages can be different.

I cannot help you with this since I have only little experience with 485 devices and always via a 232-to-485 converter connected to standard com ports.

[zorba]

I wrote a driver for WATLOW F4S controller (for LabWindowsCVI) bought WATCONNECT ( from WATLOW) used their Demo file
and wrote the driver function. Not to bad

Zorba

[Jattie]

Esentially RS232 and 485 are the same from a software perspective. The hardware is diffirent and the signal levels are diffirent and you can address diffirent devices (see RTUAddress in example below) on the same network hence the need for the modbus protocol.

Attached a full implementation of Modbus in CVI.

[ElectroLund]

Apparently with the website design, this link is now broken.

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@RobertoBozzoloRobertoBozzolo wrote:
In case your instrument is connected via RS232, here you can find an answer I posted to a similar question some time ago. 

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Can we post an update?  Also, I can't find where these community projects are located anymore.  Mod, please help!

[RobertoBozzolo]

For the life of me, I can't remember what I was pointing to in that message!

I can give you the link to my Modbus RTU programming over RS232 in CVI, the base on top of which I am developing all my instrument control programs.

As far as I know, examples published by forum members can be found in these repositories:

Example Programs

LabWindows/CVI User Group Documents

Community Documents

Example Program Drafts

(other pages may be available which I'm not aware of)