Simatic S7 - RS422

Oliver Micka

Member
Join Date
Oct 2015
Location
Hlohovec
Posts
65
Hi Guys..
I have a new project in my work..
So I must read and write data via RS422 only in Siemens CPU ( 315 2dp) and sended data from Rs422 to Profibus ( Big Display )
But i dont have more experiences for Simatic/TIA.
Note! I am a Rockwell/AllenBradley PLC programator not Simatic.

So..What i Have..
POwerSupply 5A
Rack ( long)
CPU (315-2Dp)
CP 341- RS422/485

Profibus i have a OK When i try send data to our big display all showed OK ..
But i dont have a good feeling on this communicate..(rs422 )
How can i easily connfigure Function Blocks to communicate between CPU and device which have a RS422
many thanks..
 
The CP341 is usually used together with a socalled "loadable driver" for f.ex. Modbus.
The CP340 is a bit simpler since it only supports pure ASCII.

So what is the "big display" communicating with ? Modbus, ASCII, or something else ?

edit:
Woops, I missed this:
Profibus i have a OK When i try send data to our big display all showed OK ..
Now I dont get it. You have a Profibus connection which works OK. Then why go via RS422 and the CP341 ???
 
The CP341 is usually used together with a socalled "loadable driver" for f.ex. Modbus.
The CP340 is a bit simpler since it only supports pure ASCII.

So what is the "big display" communicating with ? Modbus, ASCII, or something else ?

edit:
Woops, I missed this:

Now I dont get it. You have a Profibus connection which works OK. Then why go via RS422 and the CP341 ???

So .. I have a laser which measuring length .. this laser have communication only via RS422 ..
I need to show length data from laser to big display.
(Big Display have Profibus - comm between PLC and Display is OK )
Now i must try create PLC program which will convert data from Rs422 to Profibus..
 
The CP341 is usually used together with a socalled "loadable driver" for f.ex. Modbus.
The CP340 is a bit simpler since it only supports pure ASCII.

So what is the "big display" communicating with ? Modbus, ASCII, or something else ?

edit:
Woops, I missed this:

Now I dont get it. You have a Profibus connection which works OK. Then why go via RS422 and the CP341 ???

So what is the laser communicating with ? Modbus, ASCII, or something else ?

Jesper.... I think is a Modbus
 
S7-300 support for modbus is horrible. Siemens is not even a member of the modbus organization - that's how much they care.

I suggest getting rid of the CP341 module and putting in a profibus to modbus gateway instead. It will save you lots of work.

Like this HMS Anybus gateway:
http://www.anybus.com/support/file-doc-downloads/communicator-specific/?ordercode=AB7000

I haven't any used that gateway but I've heard good things in general about the Anybus gateways (from people that used them in projects).

This is a video showing you how to configure the gateway.
https://www.youtube.com/watch?v=mRg-zFkKCDE
.
 
Last edited:
An alternative cheaper Modbus driver

I think the HMS Anybus communicator gateway is cheaper than the driver and the simple CP340.

And it's faster to setup as you don't need to program anything, just configure what areas you want to read and write. Then you just access the values directly from the S7-300.

So no need for any programming on the S7-300 to get the communication going. The way Siemens should have done it and more similar to what they have done on the newer CPUs with modbus tcp.
 
According to post #1 he has the CP341 already.

Yes, but if it's unused he could perhaps return it. Or sell it on ebay.

Unless his labor is free and he has a lot of time, it is often better to cut one's losses early.

Given the cost of the CP341 and license required as well as the programming hours to make it work, I would for sure look at the gateway solution. The total cost of the project involves time as well.

I don't have the exact price but the Anybus gateway would be around 450 EUR / $450. I think the one needed has the part number AB7000. They are all priced similarly and they have a gateway for almost any bus. For instance ethernet/ip, modbus rtu, modbus tcp, profinet, profibus, can bus, controlnet, ethercat, devicenet.

.
 
Last edited:

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