OPC client code

[Mandar 0]

Hi, We have an application that triggers batches in FTBatch system. This is a dot Net based application created for our client. Now the client wants to see some data from the PLC on this applications UI. I have a ControlLogix with RSLinx Classic Gateway. I was thinking of picking up the data from the PLC via the RSLinx Classic Gateway OPC and display. Is there any free OPC client code or component available? My dot Net programmers are not familiar with OPC. I need something that is easy to configure and use. Even something like a component that can be called to fetch the data can do. Kindly advise as to how I can acheive this. Regards

[paulengr 44]

Right from the start you're in trouble. OPC is based on the COM/DCOM object model. dotNET is based on dotNET and doesn't play well with others, ANY others. The reference code library from the OPC Foundation includes a library that compiles into a DLL. It's not a standard, just a reference way to do things. However, EVERY OPC Client out there, including RS Linx contains a compiled version of it some place in their code base. It's relatively easy to use and all the documentation that you find refers to roughly the same DLL. The full title is "Data Access Automation DLL", and the file name is always something similar like "OPCDAA.DLL". There are dozens of companies that somehow claim that they have a wrapper that makes it "easier" to use, whatever that means. Their wrappers implement the same interface all over again except by slightly altering the names of things. Regardless, head on over to opcconnect.com. They document pretty much any tool kit out there with respect to OPC that's available, free or not.

[Mark- 17]

Hi, >However, EVERY OPC Client out there... Sorry, that is not so. OPC has two interface methods, custom and automation. If you are using the automation interface, you need the wrapper DLL. If you are using the custom interface, you do not need the wrapper DLL. Good luck, Mark http://www.peakhmi.com/