todd@islenet.UUCP (04/21/84)
I recently ordered STSC APL*PLUS/PC to aid me in my quest to rid myself
of mainframe dependency for statistical and complex graphics jobs.
I decided a couple of days ago that it would be nice to have a joystick
for use with APL*PLUS/PC graphics on my PC. Being too cheap (and broke
after paying for APL*PLUS/PC) I decided to build my own joystick following
the specs detailed on pages 1-211 thru 1-216 of the version 2.02 PC
Technical Reference manual.
The specs call for 0-100k ohm pots so I grabbed one of two lying
around and built the joystick. A quick check on a multimeter showed
that the pots used ranged between 250 ohms and 101k ohms. Obviously
I was not going to get a zero (0) reading on my PC. I accepted that.
The high end looked ok though. WRONG. After plugging it into my PC
I went into BASICA and wrote a short routine to check the joystick.
I found the following ranges:
x-axis 3 - 112
y-axis 3 - 101
The 3's were expected. The 112 and 101 were not. A 250-255 high
end should have appeared. What happened? Well, you can check out
back issues of PC Tech Journal (two part article in the Jan 84 and
Feb 84 issues) for the full answer. To make a long story short,
don't expect the game adapter (I have the AST Sixpack option, but
this is true for all adapters) to work with joysticks as speced.
It turns out that most joystick makers are using 250k- or 300k ohm
pots to make their wares. Check out how your particular system
works with different pots before soldering (I should have, but
I figured the tech manual would not lead me astray).
Todd Ogasawara -- University of Hawaii -- Dept. of Psychology
{ dual,vortex,uhpgvax }!islenet!todd