Siemens S7 - RS485 ASCII

[DLMUK]

Hi

If I wanted to put a pure RS485 ASCII string into an S7 PLC (not something I have done before) and then pick out a section of this string, how would you go about doing it?

I assume if I had a 300 I would add a CP340 (my baud rate is 19.2k so should be fine) and then added the Port config and receive data blocks to my project then this would encapsulate the received data into a tag in the associated DB. But how would I then pick out bits of data from the tag with the entire data string in?

Thanks

 

[KalleOlsen]

Are the bits allways in a fixed place in the data area?

If yes, it is very simple; give the DB a symbolic name, and define the contents also with symbolic names.

Use the bit in the code like this:

A "dbRecvData".TheBitIAmCuriousOn
= WhateverBit


If you use it as an interlock, you should have some kind of validity check. Like a timeout since last received data pack.

Kalle

 

[Pudden]

You could also use a gateway, such as the Anybus Communicator and in the gateway you could do the filtering of the ASCII string and place the data on Profibus/Profinet:
Profibus:
http://www.anybus.com/support/support.asp?PID=104&ProductType=Anybus Communicator
Profinet:
http://www.anybus.com/support/support.asp?PID=345&ProductType=Anybus Communicator

My 2 cents

//Me