Siemens S7 300 PLC Labview Communication

[sivaramkumar]

Hi.

I am using a CP-343 communications processor to connect the S7 300 to industrial ethernet. Now can I commnicate directly from Labview to the PLC?

We are plan to use ethernet communication (our TCP VI's). 

Which type of command we need to ues. whether we need to form a MODBUS protocol command.

Thanks

Siva

[rolfk]

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sivaramkumar wrote:
Hi.

I am using a CP-343 communications processor to connect the S7 300 to industrial ethernet. Now can I commnicate directly from Labview to the PLC?

We are plan to use ethernet communication (our TCP VI's). 

Which type of command we need to ues. whether we need to form a MODBUS protocol command.

---

Siemens S7 supports all kinds of protocols. Some are built in from start and are usually Siemens specific protocols whose specs are not always easy to come by, others can be purchased and installed on the communication processor seperately such as Modbus. Once you have the Modbus library installed on your S7 you can simply use the Modbus VIs downloadable from the NI site to communicate with your S7 datablocks.

It is a strict IO access meaning you can read and write IO registers and memory datablocks, but not interfere with the actual programm on the S7 in other ways.

Using Modbus is simply and hard at the same time, since Modbus uses various datatypes with different address ranges that are mapped in some way to the items in the target hardware. This mapping can be tedious to work out correctly since the documentation of devices is sometimes quite a bit unclear about how exactly that has been done by the manufacturer.

There are many other Ethernet protocols that are available or can be installed on a S7 such as Profibus Ethernet, EtherCat, Industrial Ethernet, etc. Most of these while technically possible to be implemented on top of the native TCP LabVIEW nodes are rather complicated and therefore anything but trivial to create a VI library for.

Your best bet really is to either use Modbus or an OPC Server that implements the native access to the PLC.

Rolf  Kalbermatter

Message Edited by rolfk on 03-12-2009 09:07 AM

[jamesgpeck]

Does a forum for asking Siemes S7 questions exist?

[Mathan]

Post your query here in LabVIEW forum for more people looking into it.

[carlosxyz]

I am starting to work something like that, But my PLC does not have a module communication, but it has a MPI comunication built in, So I decide to do a MPI net for my engineering degree, if you are interesting to talk about it,  you can add me to your msn : carlosxyz arroba msn dot com.

bye

[rolfk]

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carlosxyz wrote:

I am starting to work something like that, But my PLC does not have a module communication, but it has a MPI comunication built in, So I decide to do a MPI net for my engineering degree, if you are interesting to talk about it,  you can add me to your msn : carlosxyz arroba msn dot com.

bye

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There is a VI library on here that is a MPU communication library using RS-232. What would your solution add to this?

Rolf Kalbermatter

[rolfk]

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rolfk wrote:

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carlosxyz wrote:

I am starting to work something like that, But my PLC does not have a module communication, but it has a MPI comunication built in, So I decide to do a MPI net for my engineering degree, if you are interesting to talk about it,  you can add me to your msn : carlosxyz arroba msn dot com.

bye

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There is a VI library on here that is a MPU communication library using RS-232. What would your solution add to this?

Rolf Kalbermatter

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Sorry I did mean MPI compatible.

Rolf Kalbermatter

[effgee]

Hi Siva

I beleive what you are trying to do is possible, I have read posts on other forums of people that have suceeded.

You should search the Siemens website for information like this, although this exact link relates to the integrated ethernet ("PN") port available on some more expensive cpus, so you would have to call different FBs on on the siemens cpu.

https://support.automation.siemens.com/WW/livelink.exe/29737950?func=ll&objId=32038773&objAction=csV...

You don't need to "form a MODBUS protocol command.". There is a modus library available from Siemens but it costs thousands of dollars.

It really comes down to exact what you want to do. If you just want to read and write a couple of data bytes or even a whole block of data, direct tcp access is feasible. However, if you wish to read a large number of addresses, or will be changing your project often, you may be best to use OPC or modbus