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Path: utzoo!linus!philabs!cmcl2!seismo!columbia!caip!cbmvax!daveh
From: daveh@cbmvax.cbm.UUCP (Dave Haynie)
Newsgroups: net.micro.cpm
Subject: Re: Re: Re: Commodore 128 Mouse Interface
Message-ID: <389@cbmvax.cbmvax.cbm.UUCP>
Date: Wed, 11-Jun-86 18:08:54 EDT
Article-I.D.: cbmvax.389
Posted: Wed Jun 11 18:08:54 1986
Date-Received: Sat, 14-Jun-86 05:15:23 EDT
References: <1089@brl-smoke.ARPA>
Organization: Commodore Technology, West Chester, PA
Lines: 58

> 
> I plugged the C-128 mouse into the rig of my own design and manufacture
> for a Z-100.   I also plugged a regular joystick into the mouse program.
> I did not put the mouse on a scope, but the results are conclusive:
> The C-128 is not a real mouse, but is an inverted tracball (probably
> using the same IC that is in the tracball too).  It does not yield any
> stepping increments or my custom software would have been able to detect
> it.    A REAL mouse costs money to make, the C-128 is cheap.
> The Commodore man is full of it, you can check it out for yourself.
> 
> Cheers,
> Gern
> -------

Maybe you should have scoped it out.  The Commodore Mouse is in some ways
a real mouse and in some ways not, of course depending upon what you consider
a "real" mouse.  The mouse workings are very cheap in most everyone's mouse;
they simply consist of two circular wheels alternately transparent and 
opaque, which cause two phototransistors to pluse in proportion to the
velocity at which the mouse moves.  The expensive part comes in the mouse
interface, which generally transmits some good and meaningful velocity
information in a form that the computer can accept.  Up to this point, a
trackball does something very similar, and the two are really interchangable.

Now the interface on the CBM mouse is a custom microprocessor that sits out
in the mouse and watches the motion of the vanes.  It will pulse a four
bit digital TTL level signal which corresponds to the 4 bits of joystick
information all Commodore consumer type computers accept.  Thus it is 
compatible with joystick software, at least to a degree.  The main problem
is that the pulsed digital lines can easily get saturated when moving the
mouse; this seems to happen even at reasonably slow speeds.  Also, even a
program written specifically to read the mouse is going to look sloppy as
compared to the same thing with a standard quadrature mouse, the digital
pulsing takes lots of processor time to scan correctly, and it still
doesn't convey the same resolution of information available in the mouse
that you're thinking of.

Most arcade-style trackballs take an even simpler route, and don't pulse the
digital output at all; they look just like digital joysticks.  That's what
you get for buying a Commodore/Atari/ETC COMPATIBLE trackball.  There are
also trackballs that generate a quadrature output compatible with the mouse
output on an Amiga or MAC machine. 

The bottom line is that the current Commodore Mouse, as intended for C64 and
C128 style computers, is a compromise between full mouse functionality and
compatibility with software that's out there.

-- 
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Dave Haynie    {caip,ihnp4,allegra,seismo}!cbmvax!daveh

"As a dreamer of dreams and a travellin' man, I had chalked up many a mile."
"I read dozens of books about heros and crooks, and I learned much from both 
	of their styles.."
						-Jimmy Buffett

	These opinions are my own, though for a small fee they be yours too.
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