[nSLUG] Re: External temperature sensor (Gerald)

Mike Spencer mspencer at tallships.ca
Mon Dec 10 13:37:26 AST 2007

Dan wrote:

> I hooked up the "thermistor + joystick port" type sensor on my  
> Apple //c twenty years ago and it worked great.

Ah, but that was easier, Dan, if my quick browse over the referenced
article wasn't to hasty.  The Apple II port mapped an input voltage of
0-15V linearly onto 0-256 in the relevant I/O byte.  After hanging a
pendulum on a rotary rheostat and hooking up a battery, you could
write a BASIC program to read the port at regular intervals, plot the
data against time and have a very elegant sinusoidal demo of both
physics and programming.  The Apple II had great teaching potential.
In fact, I'm pretty sure I saw one with a black (!) case and Bell &
Howell marque [1] set up at the TUNS CAD-CAM center circa 1985 with a
bunch of cute digital edu-toys and gadgets scattered around it.

I've been irritated for years that there was no similar, easy-to-use,
analog-to-digital port on a PC.  The joystick article seems to suggest
that there's a way to do this kind of thing after all without getting
onto the GPI Bus.  Interestingly, the Osborne 1 had an IEEE-488 (aka
GPIB) edge connector on the front panel and the O1 User Manual
included details of talking to the BIOS driver that wasr  a standard
part of the O1 O/S.

In any case, thanks Benoit. I've saved the article and look forward to
doing some widgety hacking that's been lurking in the Mumble Bin for

- Mike

[1] See http://www.macgeek.org/museum/bhapple2plus/index.html

Michael Spencer                  Nova Scotia, Canada       .~. 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

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