RS232 to USB with Tia Portal Modules.

Big_Robo

Member
Join Date
Nov 2016
Location
England
Posts
81
Hi everyone.

I have been doing some reading and getting mixed results.

Here is my question. I have a RS232 module on my PLC. I want to connect that to a program running on a PC threw a USB adapter. Signals will be send and receive is it possible or am I wasting my time.

Thanks
 
I did some RS232 interface work in TIA last year and it seems to work OK once I turned off the flow control. The PC end will need a serial to usb adaptor and as far as the PLC is concerned it just speaks RS232.

What do you actually need to achieve?

Nick
 
Hi Nick thanks for the reply.

Yeah pc has a usb to series adapter. The PC has a program that send job codes and scale weight to the PLC. I have migrated an old S7 classic program so all nessary blocks are there just it doesn't seem to want to play ball.
 
RS232 only describes the hardware. You will need to know what data is transferred and by what protocol. i.e. what message is sent, what should be done with it and what response is expected. I used a terminal emulator program that allowed forwarding one port to another on my laptop to help get things setup but I can't remember what program that was.

Nick

I think the program I used was Termite: https://www.compuphase.com/software_termite.htm
 
Last edited:
Hi Nick. Sorry about the vague answer. I am using Freeport to send and receive ASCii strings. These strings are read in the PLC and does the required function e.g. ZERO (that would set scales to zero)

I will have a look at that software later. Thankyou
 
I'm not familiar with Freeport but if all it does is send out ASCII strings then it should be doable.

There will be a set of function blocks provided by Siemens that go with your chosen hardware that handle port initialisation, send data, recieve data etc. There is likely to be a demo program on the Siemens website for your chosen hardware.

To make my system work I programmed a state sequence that first handled initialisation and then cycled through a sequence. yours might be something like:

Initialise port
Wait for new data
Read data
Decode instruction
clear buffer
Send response
Go to wait for new data

I than wrote two routines in SCL to handle the ASCII message creation and decode.

Nick
 

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