Hi,

Briefly, We have made HMI connected to PLC via opc server. Now that we have to use Modbus Tcp or RTU instead OPC Server. i need some information.

First of all, How the topology should be?
is Modbus slave used for server or Modbus Master?

And we will develop our own Modbus Connection libraries with c++.

 

Hi,

Most people today are going the other way of using OPC solution instead of creating a custom driver. It provides a more flexible solution for less long term cost.

Check out MatrikonOPC's Server for Modbus supports Modbus TCP and RTU flavors, and can act as both a master or slave.

http://www.matrikonopc.com/opc-drivers/opc-modbus/base-driver-details.aspx

Regards,

-Mustafa

 

Hi there,

There can only be one Master, normally, on a Modbus RTU network.
On a Modbus TCP network, there can be several masters, however they can not communicate with each other.
Master=Scanner=Client
Slave=Adapter=Server

For more information about Modbus, visit www.modbus.com

BR
Pat

 

If you do choose to go the OPC route - check out the free Ignition OPC-UA server. It includes Modbus drivers.

-----------------
Nathan Boeger
Design Simplicity Cures Engineered Complexity
http://notanotherindustrialblog.blogspot.com