PICLIST@MITVMA.MIT.EDU wrote:

> Hello all:
>
> For the next phase of my PIC project (home security), I want to have remote
> keypads communicating (only) with the master control unit.  I originally
> wanted to use RS232, but was under the impression that RS232 is difficult
> to deal with when using long runs (i.e. through a house) and multiple
> interface nodes.  For future expandability of the "network", I am leaning
> toward RS485, using a Maxim interface chip.  However, I will not run it as
> a multi-drop configuration, but as a star-type configuration, with the
> keypads running (throughout the house) directly to the master.
>
> My question is:  is my impression of RS232 unfounded?  If so, why?  Has
> anyone used RS485 in the way I want to use it?  If so, did you use a
> terminating resistor as each node to minimize reflections?  Any other
> information you could provide would be very helpful
>
> Regards,
>
> --John

You can use the RS232 for long distance but you have to make an amplifier to
use it without problems. I saw one circit sometime, that could use the RS232 in
a ddistance of 100m from the computer. Maybe, if you are intereted in this
circuit, I can search it and send you.

Carlos L.M.