The Study And Implementation Of OPC DA Server Based On COM

With the developing of computer technology, more and more software and hardware are used in industry control field and system integration becomes harder than before. So it is very necessary to use the same standard to communication for both user and vender.OPC is such a standard that we need. OPC means OLE (Object Linking and Embedding) for Process Control. OPC was put forward in solving communication between application software and vary drives of devices. It makes the work more efficient. Consequently, the repeated exploitations are reduced in the integrated system. OPC specification will be a developmental aspect about process automation's communication normal for the future.This paper describes the principal of OPC in detail. And the design and implement of OPC DA Server are also detailed explain in the paper. The software structure and implementation of OPC Server and the solutions of memory allotting and data transmitting are also explained in the paper. The server implements the functions of OPC Data Access Specification 2.0. The COM technology (COM is the core of OPC technology) was used in the implementation of OPC DA Server. The server is more flexible and extendable by using the COM interfaces and object pointers.This paper introduces the key technologies, such as the IUnknown interface and connection point technology, which were used in the implementation of OPC DA Server. The server uses the connection point to realize two-way communication between OPC server and OPC client in OPC data acquisition. And the server could manage the Group objects and Item objects. The OPC DA Server implements the functions of OPC Data Access Specification.