Ethernet devices

Integrating proprietary serial and Ethernet devices with SCADA/HMI systems
By

Stephen Friedenthal
EVSystems Data Solutions
3To write a driver, or not to write a driver? Developers don’t usually have a choice if a driver isn’t available, but new tools are making the job easier. An experienced Supervisory Control and Data Acquisition (SCADA) integrator explains how one such tool is speeding up the process of integrating OLE for Process Control (OPC) hardware.

When starting a SCADA project, developers must first identify the installed devices and controllers to determine how they will interface with the SCADA system. Most of the time, a programmable logic controller with one or more I/O drivers will be available. With OPC’s growing popularity, hardware connectivity is becoming less difficult.

However, connecting to devices that lack an available driver often presents the greatest challenge. This is especially a problem with devices that have proprietary serial and Ethernet protocols such as electronic scales, particle counters, controllers, and so forth. Developers traditionally resolved this issue by writing an I/O driver from scratch.

Consequently, developers would do well to heed this advice: Don’t bid fixed price. Creating a robust and reliable driver is not trivial, as it requires a keen understanding of hardware and software interfaces and error modes. Additionally, as OPC becomes an industry standard, it only makes sense to undertake the effort if the driver supports the OPC protocol.
Creating drivers without writing them

If developers don’t have the time or expertise to write their own drivers, they should consider using the Kepware User-Configurable (U-CON) driver, which has proven useful in two recent development projects. Figure 1 shows the U-CON transaction editor.