Thursday, December 9, 2010

Industry Standard OPC Interface





National Instruments has a large number of drivers and servers for interface applications to industrial devices such as Programmable Logic Controllers (PLCs). The drivers are available on the NI Industrial Automation OPC Servers CD as well as in all NI Developer Suite Control Editions and NI Lookout development systems.

The Industrial Automation OPC servers provide software of industry standard connectivity to a wide variety of industrial automation industrial and devices networks. An important function of industrial automation system is integrating real-time manufacturing information from plant floor devices with the HMI/SCADA system. Every device and software component would have an identical interface and speak the same language through plug and play connectivity.

In fact, hundreds of systems and devices exist in a typical plant or factory, each has own unique communication protocol and hardware interface. The Industrial Automation OPC Servers provide a consistent, an OPC interface, industry standard method for accessing real-time data from all servers provided.

The NI Industrial Automation OPC Servers reduce system development and integration cost dramatically because you do not have to spend time programming the low level communication interface to industrial automation devices.

The LabView Datalogging and Supervisory Control Module and Lookout both provide built in OPC clients capable to communicate with any OPC server on the market. The Industrial Automation OPC servers work with variety of protocols and factory-floor devices, enabling you to connect to the existing devices and systems.

OPC Data Access Automation Wrapper DLL
A reference sample of the Data Access Automation interface has been provided by the OPC foundation for the OPC foundation members use in providing an automation interface to OPC data access custom interface servers. The reference sample was provided as a DLL complete with the Visual C++ source code. And vendors also may provide the DLL directly with their product.

Vendors which choose to modify the source code, or just build the DLL from the source code must do the following prior to including or shipping the DLL:
1. Vendors must change the name of the OPC Automation DLL from OPCDAAuto.dll to a vendor specific unique name.
2. Vendors should change the name of the OPC automation IDL (opcauto.idl) file to a vendor specific unique name.
3. Vendors must change the helpstring (“OPC Automation 2.0”) in the IDL file to reflect the vendor specific OPC automation interface. The name that shows up in the Automation Type Library. Visual Basic applications which use the vendor build OPC automation interface DLL will include the DLL by using the type library.
4. Vendors must change all guid’s in the IDL file to new values that are generated by using the Guidgen tool. It is required to prevent the vendor built interface of automation library from being confused with another vendors automation library or the OPC foundation provided automation library.


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