The OPC Data Access became the widest spread standard for data exchange between industrial automation devices and the visualization and control applications. The OPC is based on Microsoft COM technology, which allows relatively good efficiency low overhead on the one side and good support within the operating system itself on the other side (number of components of Windows uses COM technology, too).

The OPS client connected to the server can choose from a number of ways to exchange data (synchronous, asynchronous, call-back notification), it can require data directly from the device or from the server cache etc. All these possibilities (and also the usage of relatively complex COM technology) makes full implementation of OPC server rather difficult. Development of OPC server is almost impossible for a small company without a team of experienced programmers and also big, rich and famous companies have significant problems with development of the server fully complying to the standard (they are usually satisfied when the server works well with their clients and they often omit other ways of data exchange). Number of companies rely on various “OPC Server Toolkits” made by third parties. This approach also often fails — although it enables implementation of the OPC server to less-experienced programmers, an absence of in-depth understanding of the standard prohibits the programmers to correctly implement the server either way. If a problem occurs, programmers usually cannot localize it, they do not know which parts of their code is called in various contexts etc.

Moravian Instruments has wide experience in implementation of OPC clients and servers and the development team carefully implemented the OPC interface. On the other side the OPC Server uses the Control Web driver interface. This interface is very efficient (it uses direct procedural API implemented in DLLs) so there is no other software layer between the driver and its user. At the same time this API is universal enough to cover all devices — communication can be synchronous or asynchronous (for devices with delayed response caused e.g. by communication delays), the driver always knows which data elements should be transferred in the particular time so it can optimize creation of protocol packets etc.

The Control Web driver interface is open and well documented. There are not only drivers implemented by Moravian Instruments, but also number of drivers implemented by third parties. These companies automatically gain the possibility to supply the OPC Server for devices, for which they already implemented the Control Web driver. If it is necessary to implement a new OPC server for some device, it is much easier and often more efficient to implement driver for Control Web than starting with the OPC server from the ground up.

Although the OPC server for Control Web drivers is a licensed product, number of drivers are available for free. Control Web driver is supplied with every DataLab IO/USB or DataLab IF/EIB device (and also drivers in the form of Active X component). If it is necessary to communicate with these devices through OPC interface, the OPC Server is available for all clients.