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From: munck@mitre-bedford.arpa (Bob Munck)
Newsgroups: net.micro
Subject: BSR computer interfaces
Message-ID: <3137@brl-smoke.ARPA>
Date: Mon, 18-Aug-86 12:20:38 EDT
Article-I.D.: brl-smok.3137
Posted: Mon Aug 18 12:20:38 1986
Date-Received: Wed, 20-Aug-86 05:10:32 EDT
Sender: news@brl-smoke.ARPA
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   A small addendum to Dan Lanciani's excellent posting on the various
BSR X-10 computer interfaces.  For many years, I've been using the OLD
Radio Shack Plug'n Power for the Color Computer.  This is a small grey
box that also uses the cassette port; the cassette recorder can then be
plugged into it and one or the other selected by a switch on the Plug'n
Power (I imagine the new version has the same capability).

   The old P'nP has a much lower level interface: it is essentially a
200KHz oscillator connected to the power lines and triggered by an
output signal from the cassette port and a zero-crossing detector that
pulses the cassette input when the power line current crosses zero (i.e.
once every 1/120 second).  BSR signals are synchronized to this
zero-crossing time.  It is up to software in the CoCo to wait for the
input pulse and then generate the right coding and timing of output
pulses.  I had to reverse-engineer the RS-supplied software, with help
from Steve Ciarcia's article in Popular Electronics (RIP), to be able to
write my own support.  Two weeks after I succeeded, RAINBOW published a
program that did the same thing.

   WISH:  I'm happy with the old P'nP I have, except that I really would
like INPUT as well as output.  That is, I'd like a 200Khz detector that
would pulse an input line; I could then write software to decode the
received signal.  Given this, I could use regular command consoles (and
the telephone interface, burglar alarm interface, etc) to send commands
to the CoCo on one set of house codes and have it control devices on
another set.  It would therefore know the current state of all devices
and be able to "refresh" the state at intervals.  Also, my CoCo can
(Real Soon Now) drive IR emitters with the right signals to imitate all
the remote controllers of my stereo, VCR, LaserDisk, ceiling fan, and
artificial cat; with proper coding, I could use X-10 consoles to control
all of them as well.
                         -- Bob Munck, MITRE
ARPA: munck@mitre-bedford
uucp: {allegra,genrad,ihnp4,utzoo,philabs,decvax}!linus!mbunix!munck
work: The MITRE Corporation, MS A430, Bedford, MA 01730
      (617)271-3671       room 3A230
home: 9 Kendall Road, Lexington, MA  02173-7118
      (617)861-8846