2 ms·
OPC-DA is still big but mercifully slowly and surely replaced by OPC-UA, which is properly portable. OPC-DA essentially operated a lot like TWAIN - it specifie
by p_l 3y ago
OPC-DA is still big but mercifully slowly and surely replaced by OPC-UA, which is properly portable.
OPC-DA essentially operated a lot like TWAIN - it specified an interface for OLE-loadable DLL to load, which would then implement actual communication driver for your infrastructure. OPC-UA describes its own protocol to talk between devices.
- mike_hearn 3y agoI thought DCOM i.e. wire protocols were a big part of OPC too. But maybe it evolved in that direction over time? Like, if the COM interface is simple enough they realized you don't need a driver if DCOM is doing what the driver would do anyway.
- p_l 3y agoNope, you install an OLE control on the system that wants to communicate, then tell the SCADA/etc application to use it, and the control talks vendor-specific protocol. Newer OPC-UA capable devices could arguably run like that (definitely enough power, even without going for the ones that have full Linux system with Docker), but those tend to run OPC-UA instead which is way more capable and interoperable.
- mike_hearn 3y agoHuh, I wonder what this sort of thing is about then: https://www.matrikonopc.com/dcom-configuration-opc.aspx https://www.matrikonopc.com/dcom-configuration-opc.aspx
- p_l 3y agoIt's essentially a proprietary proxy + tunnel - on the client, you install their COM object as OPC service, then it goes over tunnel to a server process which talks to actual vendor OPC DCOM library using local COM. Understandable when configuring security can be a big PITA.