Hi,
Use Ethernet for the communications, and use Ethernet to RS232 converters to interface to any non Ethernet capable PLC's or devices.

Remember the PLC's are doing the process control and your VFP app would be doing the SCADA (Supervisory Control and Data Acquisition) side of things.
I did similar things with the plant control for Cotton Gins about 10-15 years ago, after the initial commissioning period (2 days) I have never been back and they are still running.

These plants are in remote locations with bad power feeds, so I used sine wave power filters and/or true online UPS's and the owners just change the batteries every 18 months.


>I'm looking into an industrial application that would require reading some remote temperatures, and controlling a few motors through relays. Basically I want to build a VFP application that does "normal" business stuff, but in addition ... monitor and control (to a minor extent) some remote gear. I read a bit on the "Raspberry Pi" microcomputer, but thought that I saw some issues that pushed me away. I also found the "Arduino" ... another computer on a chip device that supported some serial communication. The bottom line on my quick review was that I could write my code in VFP faster than I could write it in Python3 or C++ (which the two mentioned use respectively), and all I really need to build myself a Programable Logic Controller ("PLC") is VFP, access to a serial port, a handful of relays and temperature probes, a big spool of wire and some electrical connectors.
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>Oh yea ... I also need to be pointed to some appropriate literature that can tell me how to make this all happen. I don't have any details on the specifics of the project, as there is no project. I thought that if I picked up some capability along these lines, that I could go out and find a project.
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>Actually I did something a lot like this many years ago in a Clipper program that I wrote to talk to a "smart valve". It needed a special board to hook up to, that got installed inside the PC that was used to run the process. I was talking over a couple of rs232 serial lines at the time, "directly" from my Clipper app.
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>Any thoughts on where to pick up info on generating serial input/output to multiple devices from my VFP code, and what to look out for once I get past the edge of my computer?
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>Bob