How to communicate with a PLC?

The following questions must be asked before you select the method for PLC communication:

  • HW Protocol – RS232, Profibus, DeviceNet, io or  tcp/ip?
  • SW Protocol – custom, OPC or vendor protocol

In Scorpion there are a multitude of communication methods built-in and most of this is done without too much work. The most important tool for communication is the built-in python framework and the built in tdvcmdprotocol supporting tcp/ip and rs-232.

RS-232 Communication

There are two choices: Use the built-in RS232TDVCmdProtocol. This is very good no programming option.

Read more…

The other option with RS-232 is to write your own serialport decoder in Python. Read more…

Profibus and DeviceNet

This is a “Siemens” protocol. This is supported using OPC. To use this option requires that you buy interface cards from the bus vendors. All these solutions provide an OPC-Server.  Scorpion provides provide general client access to these servers.

Read more…

Digital IO

There are many ways of doing this. A popular approach is to interface with the Advantech products with the products Adam-6060 or PCI-1370. The adam-6060 provides io over ethernet and pci-1370 provides fast io based on an pci-card.

TCP-IP Communication

InternetMessenger is one choice.  Can be difficult use – it require that this protocol must be implemented on the PLC.

Read more…

The best choice is normally a custom tcp/ip protocol implemented in python.

Read more…




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