Hi,

I am developing a Modbus server module. This server module will get the request from the client Modbus module which is basically a hard ware device.

So the server module will have to identify the request and accordingly process. The communication between the server and client is socket programming with Modbus protocol wrapped with TCP.

I have develop the TCP server socket.

The problem I am facing with the framing and de-framing of the Modbus packet.

So could any one please provide me the logic or the source code in cpp which will do the Modbus framing and de-framing.

Thanks In Advance for your help.

 

If you look on Sourceforge you will find lots of Modbus implementations. Also, you can download the specs from the Modbus web site. The specs are very well written, and I would say the most clearly defined that I have seen in the industry.

Something you need to be clear about however is Modbus/TCP versus "Modbus over TCP". The former is the official protocol for Ethernet. The latter could mean Modbus/RTU (meant for RS-232 or RS-485) tunnelled over TCP. The formats are slightly different.

The protocol itself is very simple. The main work is actually checking for errors (e.g. is the requested function implemented, is the address in range, etc.). In Python the whole thing is a couple of dozen lines of code. C++ would probably be several times as much, but it is quite doable once you understand the protocol.

 

Our Modbus implementation is here:
http://pvbrowser.org/pvbrowser/sf/manual/rllib/html/classrlModbus.html

It is part of
http://pvbrowser.org

 

BTW, would it be possible to integrate pvbrowser int ROOT (http://root.cern.ch )??

It would be nice to use the "pvbrowser" with CINT scripting (CINT ->
C/C++ interpreter)

Regards

Armin Steinhoff

PS: ROOT works with Linux, Windows and now with QNX 6.4

 

At the moment we do not have any contact with cern. If you could arrange contact with cern you are welcome.

pvbrowser is a framework for HMI/SCADA.

It's libraries are written in C++.
You can use any foreign C/C++ libraries within pvbrowser. It should also be possible to use our libs within the cern root project.

You will have to test if our rllib (C++) works together with CINT.

 

I have read a little bit about ROOT.

It can produce PNG or JPG output, thus it can be used like we use gnuplot in pvbrowser. You can even program your ROOT application within your pvserver.