Thomas J Macauley wrote: > estimate that he has about a year of serious study before he can > piece together what he wants. > I would recommend that he look to a major PLC supplier for a solution. > (Please don't take this as an insult -- I'm working down that road myself.) I agree. I've been working on my application for a year now. > Incidentally, Microchip is supposed to be coming out with > a PIC with a CAN interface. Hmm. May have enough poke to run CANbus, but I guess it would be stretched to run the application protocols built upon CANbus. I don't bother getting excited about chips before see a sample. I've seen too many delivery dates redshift into the distance. > Also, while CAN is a good networking system, > there are some environments where field busses are NOT a good idea. Such as? > I'm still not sure if I like the idea of a network controlling the brakes in a car. You may be too late! CAN originally meant Car Area Network, developed to reduce the kilometres of wiring in a typical car. After so much design effort, it was adopted for use in other areas and renamed as the more generic Control Area Network. It may well make cars safer and cheaper, as there are less wires to make a mistakenly connect. > PC as a controller... Think how often your PC crashes, > then decide if your factory can deal with that kind of down time. Yep. Dead right! A company called SoftPLC specialise in software to turn PCs into PLCs. They are also aware how crappy PCs can be, even down at BIOS level. So they use entirely their own BIOS code to do things that the native BIOS would do. The only time they call the native BIOS is to check the keyboard for the stop bu tton (ESC). They reckon if someone finds a bug in their BIOS code, they'll fix it in 24hrs. They've found and reported bugs in other PC makers BIOS code, and the manufacturers can't be bothered to fix it. I managed to get their PLC software kit sewed to the Honeywell SDS DeviceNet kit over a few caffeine-soaked days. Much quicker than inventing the whole damn lot myself.