Hello Readers,

I need to send 84 bytes with measurement values (2-byte-Words) to a gateway, in order that a profibus master can take the values. The profibus master should also be able to send 16 bytes of data which should be received by the pc via rs232.

Now, I am using a Siemens Simatic S7-200 together with the EM 277 Profibus Slave. On the S7-200 (CPU 224) I have a modbus rtu client running (which was once on the free Tips and Tricks CD). So it is possible to send my data to specific addresses on the Siemens CPU. As there is the EM 277 connected to the CPU, any Profibus Master can get the values from the specific adresses by polling.

Instead of these combination I wanted to use one of the commercial gateways. I tested 2 of them:

Comsoft XPS-E

It worked, but I cannot transfer 64 bytes as a whole, because the profibus is much faster and therefore gets the 64 bytes in peaces. Therefore the profibus master would need additional programming in order to build the 64 bytes block from the peaces. There is also a mode with a trigger byte on the Comsoft XPS-E, which could be used to send a block only after the trigger byte is sent. But this is not usefull for me, because the trigger is only one byte and I want to transfer binary data.

Deutschmann Unigate:

According to the description, the Deutschmann Unigate is capable to work as Profibus Client on one side and as Modbus Master or Client on the other side. However, I could not operate it as modbus client, so that I can send and get data via RS232. There was always a communication error. From the hotline I got different answers. One said, that it is not possible to use it the way I described above. Another from the hotline said, that it should be possible. So I gave the gateway to another company, which also needed such a gateway. However, their computer specialist could not make it running, too.

There are some other gateways on the market, but they are too expensive for my applications (> 1000 EUR/USD).

Any experiences which such gateways?

Greetings

Ernst

 

There is the AnyBus gateway:

http://www.anybus.com/eng/products/abxoverview.asp

But I have no experience with it.

 

Have a look at Prosoft Technology's ProLinx line of products. They have a Profibus master and slave to Modbus master/slave gateway.

http://www.prolinxgateways.com/products/4105.html

- CH

 

Look for ProLinx gateways.

 

Next you have the link to a Profibus <--> RS232 gateway that I used (with S-300 and 400 but not with 200).
In the last project we were receiving (from gateway) 135 bytes of data and send out 5 bytes (as I remember). Price is about 400$.

http://www.mksinst.com/cgi-bin/product.exe?pid=PFB366

It worked well and was relatively easy to set it up. It is small, has rotary switches for Profibus address, stupid proof connectors and good visual (LED) status indicators. Company was very helpful and we got free test unit(s). MKS has offices all over the world. This is the good part.

The problems: device is IP-20 so you need an enclosure to use it on the field. At the beginning we had to work with MKS to solve some bugs related to the diagnostic bytes. (MKS still says it is an S7-400 inconsistency and they applied a “cover-up” so it looks OK.) You might have some problems when you use it on 200. Maybe yes, maybe no.

During operation we observed that in about 0.2% cases (1 in 500) the amount of data received was not what we expected. The length was 1 byte shorter (very seldom 2 bytes shorter). The lost byte was sometime at the beginning, sometimes at the end and sometimes in the middle in random positions. I don’t know if your application is so tough (ours required accuracy of 1 in 10000!). It seems to be a receiving / conversion problem on the serial side.

Now, really talking I got lost in your explanations about “modbus rtu client running” and the “Profibus Master can get the values from the specific adresses by polling”. I used this gateway in a classic way: configure-it in the hardware configuration (using the provided gsd file) and then you access the Profibus slave (gateway) with regular PI / PQ access instructions (load / transfer). Maybe you are talking about something S7-200 specific. I never worked with 200.

If you get one and have problems configuring it send me an email at [email protected] .

ValRo

 

You could try here:

http://www.ctiweb.co.uk/pb100.htm

They can do bespoke software if the standard unit doesn't cover your app.