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From: dickow@ui3.UUCP
Newsgroups: comp.sys.cbm
Subject: Re: Zapper for C64
Message-ID: <60008@ui3.UUCP>
Date: Mon, 22-Dec-86 13:11:02 EST
Article-I.D.: ui3.60008
Posted: Mon Dec 22 13:11:02 1986
Date-Received: Fri, 2-Jan-87 20:57:06 EST
References: <60@popeye.UUCP>
Organization: MRC, University of Idaho
Lines: 19

...
   Concerning the question about a ZAPPER light gun for the C64...
     I can't say for certain that there isn't a "light gun" such as this
available, but I would be a little surprised. I say this only because light
pens (direct contact to screen) to date have been slightly problematic on
the C64. It takes extra hardware/fast photodiodes in order to reduce the
horizontal 'jitter' that occurs. That is, getting readings on the verticle
coordinate (even with cheapo $1.50 pens you can make from two parts purchased
at Radio Shack) is a cinch. The horizontal readings are bonkers. Basically
you have to deal with an 8 bit resolution to determine a point on a 320 pixel
wide screen. You can get better hdwr and do interrupts and ML averaging and
most-frequently-returned-data routines and still get erratic results in my
experience. My work with the SYMTEC light pen on the Apple IIe is also prone
to some of the same problems. All in all I might be quite dissapointed in
a light target gun for game applications on any system, but I'm willing to be
proved wrong.

Bob Dickow, University of Idaho School of Music
egg-id!ui3!dickow