Hey all,

I've been designing and implementing a temperature control system for my
university.

It is as follows:

There are two remote terminal units powered by PIC32s in two different
chambers. They are connected to a desktop PC through CAT3 ethernet cables i=
n
a multidrop configuration. The network is RS485 and the protocol is MODBUS.

I recently decided to use XBee instead of a physical connection since it
will make expansion much much easier.

Basically, the desktop computer is running MODBUS (master) software and is
monitoring temperature, humidity, and so on from each of the RTUs and is
signalling them to control relays to turn heaters and humidifiers on and
off.

* I would like to implement MODBUS over XBee. Would this be relatively easy
to interface to a PIC32 on the RTU end?

* Also, how would I go about connecting an XBee module to the desktop
computer? Are there any adapters available?

* Currently, the MODBUS software is communicating to a physical serial port
(RS232) on the computer which is connected to a RS485 converter module whic=
h
is connected to the multidrop cable. Therefore, I'd need to emulate a seria=
l
port on the desktop which communicates with the XBee. How difficult would
this be to do? Is this *unheard* of?

Do you guys have any other suggestions for this?
--=20
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