I would like to know if an off-the-shelf RS-232 to RS-485 converter can be used to connect a PC with the Siemens programming software for the S7 family to a Siemens PLC S7 200 (using PPI) and S7 300/400 using MPI.

Thank you all in advance,

Juan.

 

I do not know for S7-300 or S7-400 but there is a web page in Spanish where it explains how to build your own PPI cable so you will be able of connecting you PC to S7-200.

http://www.geocities.com/siemens_simatic/links.html

As you can see in this web page what they are really doing is converting 232 to TTL and then to 485.

Try directly with your converter and if it does not work look deeply there to see differences between your converter and schema.

I have not tested it myself but it looks good.

Good luck.

Tell if it works please.

 

Hello!
What I understand is you cannot use off-the-shelf converters. Its a proprietory conversion to Siemens.

 

Hello!

What I understand is you cannot use off-the-shelf converters. Its a proprietory conversion to Siemens.

 

Hi Juan,

The answer is yes and no... I'm explain:

* For s7200 it's possible to use an RS232 to 485 adapter for programming,
testing and viewing anything on plc, but you can pick driver enable of RS485
chip from TX_DATA and not from RTS as normal for these devices.

I suggest to download my drawing from this forum:

http://www.plcforum.it/upload/index.php?action=downloadfile&filename=S7200CN
V.pdf

* For S7300 nothing is possible because MPI ports runs at 187,5 Kbps, more
faster than normal serial port, and there is a special coms protocol like as
token passing... sorry.

Best regards

Gabriele Corrieri
mailto:[email protected]

 

Dear Juan

I have developed application which can communicate with S7 plc through communication cable of S7 which is normally peple using for communicating with Microwin software for Ladder programming. I have used it for data acquisition purpose. What do u want give me more details? I may help u.

Regards

Sanjay Patel

 

Hi Sanjay,

This application is based on a Siemens driver, or you have developed also comms driver for S7200?

If you have developed drivers I'll be interested to reiceve a copy of entire apps, if possible.

Best Regards

Gabriele Corrieri mailto:[email protected]

 

MPI and PPI are profibus protocolls. It´s not possible to have direct access to the S7 200/300/400 from pc side. A company in germany (schildknecht Elektronik) has developed a gateway (pcb or chip version) with an open documented RS232 protokoll to MPI/PPI

Try

http://www.schildknecht.info/english/e_prodbrid.htm

Thomas

 

Hi Thomas,

it's not all true: it's true that MPI and PPI are based on profibus FDL, but MPI is more similar to Profibus, because is a Token-Passing protocol, and it involve in communication all devices in network (or, at least the masters), PPI is a Profibus FDL 'children' but it isn't a Token Passing protocol because the communication is give with no determinism from one to one other device on network: so, for 200 series plc (from the oldest 211 to the newest 226XM) is possible to make an simple adaptor (for an expense no more large than 10$) that runs very well: it's have three limits: it's no permits to have other master device on network (e.g. OP, TD, other CPU), it's supports only 9600 and 19200 bps speeds and isn't no suitable for teleservice, but I'm using from three years my self made adapter with no trouble ...

The drawing is downloadable for free at: http://www.plcforum.it/upload/index.php?action=downloadfile&filename=S7200CN V.pdf

I'm avaiable for info (from 25 august, when I'm turning back from holidays).

Best Regards

Gabriele Corrieri
mailto:[email protected]

 

can you check your link, it appears to be broken.