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From: seeker@indirect.com (Stan Eker)
Subject: RSTM hacking info source
Message-ID: <D8Jp82.7Ex@indirect.com>
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Date: Sun, 14 May 1995 01:52:50 GMT
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To any others out here in 'Netland that are thinking of hacking into one of
the Rat Shack Electronic Tape Measure (called RSTM at the MIT archive),
here's a good hint:  hit your local Rat Shack and spring the $4.21 for them
to send you the service manual.  It got here in about 4 days from order.

Contained therein, you'll find schematics, PCB layout and parts placement, a
calibration procedure, various block diagrams, a troubleshooting list (in
case you blow it up), a list of all electrical and mechanical parts and
finally the pinouts of the chips used.

One handy thing Brian didn't notice, or didn't find a need for:  there's 4
pins on the 66QPF micro hidden under the LCD display meant to talk to a
serial printer.  Instead of decoding the echo timing yourself, you can
probably just tack it onto your SPI/MicroWire/I2C chain and read the results
at leisure.  Looks like the pins are brought out to solderable pads, and
you get CLK, DATA, /RTS and /CTS.  If it's open-collector/open-drain, it's
beautiful.

Even if you gut the micro out of the loop and bang the pins directly from
your 'HC11 (or whatever), the schematics will save you hours of time.  I'd
forgotten that Rat Shack sold the service manuals until someone mentioned it
recently.  All told, the $25 price is a heck of a lot cheaper than the
Polaroid experimenter's kit I'd seen, which was $70-90 or so, and I'll lay
odds that it's easier to wedge in than the Polaroid unit.  A friend had one
of the Polaroid units years ago, and had many fun evenings trying to get it
to work consistently.  No thanks!

If anyone's interested, I'll post results of what I find out via the serial
port on the RSTM.  I'm more interested in gutting the artificial stupidity
out of it, but will still play with it some before I hack the display and
microcontroller out of it.

