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David Nimmons
Wonderware and other MMI's do not use OPC to communicate with the hardware, but instead use Modbus, DH+, ControlNet, etc. OPC is used to allow external applications such as spreadsheets access to the process data, with Wonderware acting as the OPC server. For Wonderware to communicate with the LinuxPLC, all that is required is a driver for Wonderware that speaks the LinuxPLC protocol. Wonderware will then provide the OPC access. When we develop a Linux based MMI, then we have to decide whether or not to provide OPC functionality. Since so many 3rd party applications depend on OPC for access it would probably be desirable. At the plant where I work we use Aspen for our historical trending and Pavilion for advanced process control. These communicate with our Foxboro and ABB DCS's using OPC. These are both Unix based systems and if I am not mistaken the OPC server runs on the Unix machines, so it should be possible to implement OPC without requiring Windows. I, personally would prefer to come up with our own protocol and convince all the third party vendors to support it also since I hate using anything associated with Microsoft, but, reality being what it is....... Ken Irving wrote: >My hope is that those Linux MMIs will stand up to the competition on an equal (or more so basis, when they're available and demonstrable. But I have potential customers/clients who have standardized on Wonderware, for instance, and any control system that is proposed to part of their systems has to work with that system. AFAIK, that means OPC or DDE. < _______________________________________________ LinuxPLC mailing list [email protected] http://linuxplc.org/mailman/listinfo/linuxplc