Hello. I would like to establish RS-232 based serial communication between the S7-300 and a raspberry pi for a university project. As a test, I would like to begin by sending a 1 or 0 from the raspberry pi to the PLC. Just want to use the raspberry pi as a simple switch. I am well-versed in C++ and Python so that will be no problem but I have zero knowledge as to how I am going to incorporate the data sent by the raspberry pi in my ladder logic program so the PLC can respond to it. Is there a block or instruction that will read the data on the serial link and make it accessible to the ladder logic program?

Something like this? -see attachment-

I am new to TIA Portal V13 with Step 7 Professional so I would like your help setting things up. What devices/cards do I add and what instruction or block do I use for serial communication in my ladder logic program? 

Thank you in advance for your help.

ClimateController

I would like to establish RS-232 based serial communication between the S7-300 and a raspberry pi for a university project.

Hi there.

An interesting design idea you have.

From your description I think that you are moving too quickly to the software part of the project. But then again I am not an expert in these matter.  I will however ask: Are you sure you have the right hardware?

The standard DB9 connector on the S7-300 is dedicated to MPI communications on an RS485 link. Some S7-300s have a port that can be used for point-to-point communications or you can add an extension card; but even then you will have to be careful to select the RS232 link port.

I would strongly recommend the use of the S7-1200. Again you will have to buy an add on extension, but it is far less expensive. The technology is also current. You can also consider changing your link from RS232 to Ethernet. The S7-1200 has an on-board Ethernet link that can be configured/programmed for communications such as Ethernet TCP/IP.

I highly recommend you get some specifications about the PLC you intend using; ensuring you can reconfigure the communication port. Get the System Manual for that hardware.

On the program side I would advise to look into ASCII communications. If you have the TIA13 software, a search in the help files should push you in the right direction. Getting the System Manual for Step7 (TIA Portal) is also a good idea here.

I hope this is of help to you. Feel free to ask more questions for our community.

Greetings.
w

Hi there!

I agree with William B. An S7-1200 would be your best option, using its Ethernet port.

Here is an example:

http://simplyautomationized.blogspot.ro/2014/12/raspberry-pi-getting-data-from-s7-1200.html

Unfortunately, I only have access to an S7-300 (CPU 312C) with a USB-MPI adapter for programming. An ethernet port would have been brilliant but alas we will either need an extension card or an adapter of some sort. I guess it will have to be serial for now. I spent some time yesterday trying to figure out the software and I think I am making good headway.