> Suppose you want to automate some of the functions of a remote cabin. The
> usual intrusion, flood, and cold alarms, along with controls for the
lights,
> heater,etc. A very typical X10 type setup. But many, like myself, are not
> truly comfortable with X10's open loop design and their sometimey
controls.
> And as PIC enthusiasts, the challenge is interesting. As a final hitch,
we're
> functioning on limited solar power. For the sake of argument say that two
> way satellite Internet is available.

Good, now we have a reasonable problem statement.  My first take on this
problem would not be to have each tiny device do some type of IP.  I like
CAN for this application, because it is much more lightweight for the tiny
devices.  I could envision running a common bus around the cabin that
contains the two CAN wires, ground, and low voltage power like +7V regulated
at the source.  Now each tiny device only needs a 5V regulator, CAN
interface chip, a CAN-enabled micro, and a crystal and caps as overhead.
You can't beat that with IP.  One central node supplies the power to the CAN
bus and acts as the CAN to TCP/IP bridge.  This single node can afford a
more substantial controller to do a decent TCP/IP implementation.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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