On Thu, 6 Jun 2002, Micro Eng wrote:

>I've had an idea for a while. Think others have solved some of the problem
>but checking..
>
>Say i have a string of sensors, using one of the 8pin PIC's.  Three of the
>I/O ports are being used to monitor the sensors...
>
>I have say....100 of these units in a string, each 6" or so apart.
>Comm methods.  Is RS485 the best way to go? Or has someone else been
>successfull in using some one-wire multidrop method.  I know...RS485 is not
>the method...just the medium for it.  I dont need anything really fast, but
>somewhat robust and cheap of course.  Oh...only will be transmitting on this
>part of the circuit, so no need to worry about bidirectional or collisions.
>The rx side of the sensor transmitter is totally different.

I have used a modbus-like protocol like this, with up to 10 hot-pluggable
peripherals. Sony LANC control uses this system at 9600Bauds afaik. I used
1200Bauds. The line has (active) pullups and the drivers are o.c. or o.d.
I don't know about 600" but with 50V line level and up to 4800B you could
use POTS wiring up to about 20 miles or so ;-).

Peter

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