# Modbus protocol handler on PC

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#### Pravin Fatnani

We are doing a small automation project with Labview ver 5.1. In this we have to talk to 2 modbus devices - a PID controller and a Mains monitoring device. What would be the easiest way to do that? Is there any free source code/ DLL available which has functions built in for MODBUS protocol handling?

Any suggestions are most welcome.

Thanks in anticipation.
Pravin
CAT/ Indore/ India

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#### Alan Brause

You can get the pieces you need to write your own LabVIEW driver for any Modbus controller from this .llb written by Shaun Rumbell. It's written for a EuroTherm controller but can be adapted to whatever you need. You will need the register address map for your particular controller in order to get or set registers.

"http://www.users.globalnet.co.uk/~pseudo/pages/vis.html":http://www.users.globalnet.co.uk/~pseudo/pages/vis.html

Look for "EuroTherm_Comms(6.5).llb".

For specifics about the protocol itself, see
"http://www.modicon.com/85256AE8006D78AB/all/852566B70073220C85256752006EA537/$File/PI_MBUS_300.pdf":http://www.modicon.com/85256AE8006D78AB/all/852566B70073220C85256752006EA537/$File/PI_MBUS_300.pdf

Regards,

Alan Brause

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#### Luis Rios

I have used LabView 5.1 (in experimental way) to monitoring a set of numerical protection relays using Modbus RTU protocol. The implementation of the protocol or a subset of the protocol can be done by yourself in a very short developing time.

I wrote a CIN for the CRC16 calculation, if you want it, i can look for it in my old stuff archive and send to your email.

Luis Rios
[email protected]

A

#### Alan Brause

You can get the pieces you need to write your own LabVIEW driver for any Modbus controller from this .llb written by Shaun Rumbell. It's written for a EuroTherm controller but can be adapted to whatever you need. You will need the register address map for your
particular controller in order to get or set registers.

http://www.users.globalnet.co.uk/~pseudo/pages/vis.html
Look for "EuroTherm_Comms(6.5).llb".

For specifics about the protocol itself, see
http://www.modicon.com/85256AE8006D78AB/all/852566B70073220C85256752006EA537/\$File/PI_MBUS_300.pdf
Regards,

Alan Brause

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#### Pravin Fatnani

First of all thanks for your kind reply. I would be glad to have the CRC16 code from you.

Actually our idea is to have a dll which could be used by Labview as well other apllications also. Any clue in that direction?

regards,

Pravin Fatnani

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#### Anonymous

Dear Pravin I have developed one ocx which can prepare query for u as well as check the CRC ofthe response from your instrumentation. But
you have to send the information in certain format. Please give me more detail than only I can help you.

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#### Sanjay Patel

Dear Pravin

I have already developed OCX which can prepare query for you as well as check CRC of the Response of the instrument. If you want the same
please give me more details. What you want to do.

Regards

Sanjay Patel