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From: raible@cbmvax.commodore.com (Bob Raible - LSI Design)
Newsgroups: comp.sys.amiga
Subject: Yet another Atari TRAK-BALL hack
Message-ID: <15998@cbmvax.commodore.com>
Date: 21 Nov 90 02:44:25 GMT
Reply-To: raible@cbmvax.UUCP (Bob Raible - LSI Design)
Organization: Commodore Technology, West Chester, PA
Lines: 71

The following are directions for converting the Atari trakball that has
no testpoints and no socketed IC's as previously described. The device
in question is black and roughly rectangular and is labelled across the
top"ATARI     TRAK-BALL". In the rear there is a cutout which contains
a JS/TB (joystick/trakball) toggle switch, and the strain relief for the
cord. On the bottom are 4 rubber feet which conceal recessed screws.
Also, there is a paper label which on mine reads "KM483" and below this
"8". Below this label is stamped "MADE IN USA". On the top left and top
right of the top surface are two black fire buttons shaped liked
truncated triangles.

Inside, there lies a green PCB with bottom facing up towards you. Across
the top of the PCB are the cable connections, which I'll label PAD#1
thru pad#7 going from left to right. Also on left side of PCB are 2
IC's(go ahead and peek at other side,I don't mind). Topmost IC I'll
label IC#1 (16 pins) and bottom IC I'll label IC#2(14 pins). Below pads
4 and 6(labelled by atari "brown" and "blue" respectively), there are 2
thru-holes occupied on the top side of PCB by a bare wire jumper. I'll
label these thru holes TH#1 and TH#2 respectively. Directly below TH#2
is TH#3 which is connected to pad#5("violet").

First decide if second mouse fire button is desired. If not, then
existing cable is sufficient. Otherwise Amiga mouse must be
cannibalized, or joystick extension cable obtained from Radio Shack.
I'll assume you want to hook up the second fire button(look out Battle
Squadron).

Ok, here goes:

	1) Remove jumper wire between TH#1 and TH#2(separates 2 fire
	   buttons).
	2) Add 4.7K resistor(yellow-purple-red to you software types,100
	   squares of p-diffusion to fellow chip designers) between TH#2
	   and TH#3.
	3) Connect port pin #1 to IC#1,pin #6.
	   Connect port pin #2 to IC#1,pin #10.
	   Connect port pin #3 to IC#2,pin #11.
	   Connect port pin #4 to IC#2,pin #3.

	   This serves to hook up mouse vertical and horizontal, and
	   their quadratures(in that order).

	4) Port pin #5 is a no-connect, unless you want to kludge in a
	   middle mouse button(let's not get carried away).

	5) Connect port pin #6 to TH#1. This is the "hot" lead to the
	   left mouse button.

	6) Connect port pin #7 to pad #5("violet"). This hooks up +5V.

	7) Connect port pin #8 to pad #7("gray"). This hooks up GROUND.

	8) Connect port pin #9 to pad #6("blue"). THis hooks up right
	   mouse button.

Congratulations, assuming Murphy slept while you worked you now have a
genuine bargain in your hands. BTW the position of the JS/TB switch is
immaterial, we tap into the mouse signals upstream of that particular
circuitry. Enjoy!

PS: If you weren't successful then I can be reached at:
	raible@cbmvax.commodore.com(at least I think that's my address).

Big Disclaimer: plugging such a contraption into ones Amiga could blow
the +5V fuse or an 8520 CIA. So please be careful. This a home-brew hack
and not a CBM sponsored project. These instructions are merely my
recollection of the steps I took for informational purposes only. Whew,
I don't know about you, but I feel a whole lot better for having said
this.

Good luck!