🚀 go-pugleaf

Following is a file downloaded from Delphi describing the modifications I used.
It turns out the trakball internally has the right signals; the extra circuitry
changes the pulses to joystick signals. The mod basically extracts the original
pulses to make it look like the mouse.

Bruce D. Nelson            | UUCP: ...!rutgers!rochester!kodak!ektools!bruce
Eastman Kodak Company      | Voice: 716-726-7890 
901 Elmgrove Road          | Company Mail: Dept 420 Technical Support Services
Rochester, NY 14650        |
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CX22MOD.TXT

     The following instructions explain how to modify an Atari
trackball (model number CX22) to work like a mouse for the Atari
ST (complete with left and right buttons).


     To start with, if the instructions here are followed PROPERLY
(and you don't fry a chip) it should work just fine, however, I
make no claims as to the accuracy of this file, nor do I guarantee
that this will work for you.  

NOTE: This modification will NOT retain the original "trackball" 
or "joystick" modes of the ball.


WARNING:  The following ONLY applies to the model CX22 trackball!  
The CX22 can usually be identified by its case (the case matches 
the 800XL series computer) which is dark brown on top with a white 
bottom.  When in doubt, flip it over and look for a model number!

     If you have the older Atari trackball (solid black case),
don't dispare, there is also a text file on modifying it to work
like a mouse.  The file can be found in the Delphi Atari SIG if
you need it (search with TRACK as a keyword in the ST database).

Things you'll need:

*  An Atari trackball, model CX22
1  A Radio Shack joystick extension cable (part # 276-1978)
2  A low-wattage soldering iron (15 watt, or close to that)
3  A Volt-Ohm meter (you'll need to trace some wires)
4  About 2 feet of wire (small gauge will be easier to work with,
   such as the wire in the joystick cable)

     Before we get into this, if you're not familiar with 
electronics or soldering to IC's, PLEASE have someone else do this
for you.  Also, DON'T trust the colors on the wires in the Radio
Shack joystick extension cord!  Every one that I buy is different
(Radio Shack seems to use a random color coding... makes it tough
on us guys), so you'll need to trace the wires to see what pin on
the plug they go too (thats what the ohmmeter is for).

     To open up the trackball, remove the 4 screws on the bottom of
its "wings";  it still wont come apart after that because there are
2 friction-fit posts inside it (both near the center of the case, 
one at the top and the other at the bottom), pry it apart slowly 
and gently to avoid breaking them.  Once you open up the 
trackball, remove the old joystick cable (it doesn't have all the 
wires we need).  Now get your Radio Shack joystick cable and clip 
off the MALE end and discard it (the end with the metal pins 
sticking out).
     In case you don't aren't familiar with the the pin numbers of
the joystick cable (the Radio Shack cable doesn't have them
numbered, either), here's the layout:

Looking at the JOYSTICK end of the cable (female end):

         5   4   3   2   1
           9   8   7   6

     Strip about 6 inches of the outer jacket off to expose the 
individual wires (you'll need a little length to work with).
The only pin we wont be using is pin 5, so trace it first, and 
clip off it's wire (now it's out of the way for good!).  Next 
trace all the remaining wires to their plug pin numbers and write 
it down someplace.

     Look at the IC's in the trackball.  Find the one marked
LM339 (it's  a 14-pin IC sitting away from the other IC's,
directly south of where the ball sits).

     The IC's pins are numbered as follows (standard IC
numbering):
(looking at the top of the IC)

                   14 13 12 11 10 9  8
        notch -->  )
                   1  2  3  4  5  6  7

Make the following connections to it:

(Plug pin #  to  LM339 pin #)
1 - 2
2 - 1
3 - 14
4 - 13
      
     Connect the following wires to the connector that the 
original joystick cable was plugged into (look on the PC board,
the connector's pin 1 is numbered).

(plug pin # to PC board connector pin #)
8 (ground) - pin 1 (closest to center of the case)
7 (+5 v) - pin 2 (to the left of pin 1)

     Jump a lead from one connector of each fire-button pad
(right and left pads) to pin 1 on the PC board connector (in other
words, ground them).

     Make the following connections to the other side of the
fire-button pads (we're going to separate the right and left
buttons).

(plug pin # to --- pad)
 6 - left fire pad
 9 - right fire pad

     Now hook it up to the ST to make sure it works properly.
Before you close it up I recommend that you strain-relieve the
cord.  The easiest way to do this is to tie a knot in the cord
where it exits the case (this will keep it from being accidently
pulled out of the trackball).  Close it up and you're done.

Special thanks to Norm Weinress for info on the LM339 pinouts.

  -Blake Arnold (Delphi 1BLAKE)