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Modbus TCP IP Communication with Siemens S7

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We are trying to communicate with a V570 throught ethernet with a Siemens S7, but we don't get it running. Does anybode have some experience with this?

We followed the whole manual from the S7 and nothing special. I could already communicate with another v570 in the network. I would like to keep one v570 as a master and the Siemens S7 as a slave.

Some help would be very appreciated.

Regards Henri

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  • 2 weeks later...

To use Modbus TCP with unitronics is very easy. With siemens the problem i a little more big. You must to buy cp341-1 and his driver (modbus). Total cost 1500 euro. I have performed this application some years ago and it si not very easy!

I advise you to buy a Operator Panel ( i use sitek) that work as bridge. You spend 400 euro and it is very very very easy!

Best regards


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  • 2 weeks later...


Can you give an example of the the "operator panel" you mention?

I agree, Modbus in Step7 is not simple or easy and when I did it a couple years ago, the function blocks that come with the module from Siemens did not work. There were also several issues getting the software to work after the correct function blocks were found.

If I could avoid that with your suggestion, I would like it much better.

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@ Dahnuguy

The Red Lion Data Stations as well as their HMIs can serve as protocol converters. I have used a small HMI of theirs on occassion just to bridge communication.

@ Djeanry

Are you using FB100? What CPU are you using an what is the physical connection you have? What version of Step 7 are you working with? Are you using a CP343-1?

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I paid €490 for the unit. I had to order on special delivery so I think this should be the maximum anyone should pay.

Quite new to PLC programming but still found it easy to set up.

Had some problems getting 485 to work, but worked fine on 232.

(was certainly a problem on my side regarding wiring or terminating)




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