> You are re-inventing a wheel.
> There are factory automation networks, generically called field buses.
> There are far too many of them already

I'd second that opinion.
Many of them are vastly over-spec'd to cater for every situation.
RS-485 is a good physical level i/f but is restricted to a
master/slave protocol.

With all the nodes you are talking of,  I would suggest something
like CAN that has the ability to interrupt. Then you can use an
affordable cable and still get an acceptable response rate.

Steve.

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Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
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