I wonder if something like this would help... It's low speed... and the 
current is driven from an external source, not the PIC.. You can do the flow 
control in software..
http://jap.hu/electronic/pbus.html

> Looking for a simple way to have multiple PICs communicate with each other
> over distances of up to a couple hundred feet (which conservatively
> includes the vertical lengths up to the ceiling).  Currently I'd say about

-- 
with metta,
Shawn Tan
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