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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.cbm
Subject: Re: M1 Mouse
Message-ID: <352@neoucom.UUCP>
Date: Mon, 5-Jan-87 09:27:36 EST
Article-I.D.: neoucom.352
Posted: Mon Jan  5 09:27:36 1987
Date-Received: Mon, 5-Jan-87 21:53:30 EST
References: <1837@sunybcs.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 43
Summary: How the 1350 mouse works.


Hi Devon, et al;

	The 1350 mouse for the C64/C128 is the same as the mouse
that plugs into the Amiga.  It has two IR LEDs that sine though a
chopper wheel onto 4 photo transistors (two per axis).  The
transistors are set up in an arragnement such that as one moves the
mouse, they generate sqare waves that are in quadrature phase
relationship.  That is to say that as one moves the mouse forward,
one transistor's squarewave will lead the other by 90 degress.
Reversing the mouse direction will cause the phase to switch to
lagging by 90 degress.  The using one transistor output as a
trigger makes it possible to determine which direction the mouse is
moving depending on whether the other transistor's output is high
or low at the time of the trigger.  The number of triggers per
second is, of course, directly proportional to the speed the mouse
is moving.

	Now, for the neat part.  Since the mouse has four digital
outputs, these go to the same four pins as the joystick contacts.
It is possible to simply plug in the mouse and have it sort of work
like a joystick.  One one rolls the mouse, it is like repeatedly
bumping the joystick lever.  As you might guess, this doesn't work
very well.  It is possible for software to look at what is
happening and figure out what sort of input device is there by the
type of pulses coming in, but it is really easier to just have the
user indicate whether the mouse or joystick is in use.

	The new Commodore mouse is model 1351.  This one is
especially for the C64/128 and comes with a GEOS update disk (so
wait before you download all that stuff from Quantum Link).
Reportedly the 1351 has some electronic goodies inside or something
that makes it quite different.  My parents just got a 1351 for
their C64 yesterday and I haven't gotten a chance to go over to
their place and disect it yet.

  --Bill

Bill Mayhew
Division of Basic Medical Sciences
Northeastern Ohio Universities' College of Medicine
Rootstown, OH  44227  USA    phone:  216-325-2511
(wtm@neoucom.UUCP    ...!cbatt!neoucom!wtm)