BGB100@PSUVM.BITNET (Bruce Blanar) (11/28/89)
Several people have asked me to post the description of the modifications to
and Atari 2600 trackball to have it work as both a joystick and a mouse for
the ST. Below is the semi-detailed plans I wrote up to perform this mod.
Let me know if any corrections are necessary. Thanks.
Atari 2600 Trackball -----> Atari ST mouse
-------------------------------------------------------------------------------
Here are the mods necessary to convert an Atari 2600 Trackball for use
as a mouse for the ST. Notice that this mod will allow the trackball
to also function as a joystick depending on how the switch on the bottom
of the trackball is set (T=mouse, J=joystick). The only major drawback
of this mod is that the trackball has only one button...the left mouse
button. (but, hey, how many programs use the right mouse button?)
OK, here goes...
1. Figure out how to open the trackball.
There are a few (4?) screws on the bottom of the trackball. Once
the screws are out, you should be able to pry the top half off.
2. Take out the ball (looks like a billard ball!).
Look on the board for a chip marked 4019. If this chip is socketed,
you're lucky (the mod is much easier). If it is not, well...
In any case, this chip has to be removed. DON'T destroy it! It
is still needed. Normal CMOS precautions apply. Static can KILL!
--At this point, you should have the 4019 out of the circuit. If it
was not already in a socket, I would suggest putting a socket in.
3. Find the pins 1, 3, 5 and 7 on the 4019 chip. Use the diagram
below if you are not sure. Bend these pins up so that they point
either up or out to the side. These are the pins that will be used
for the 4 wires in this mod. They will not have to be reinserted
into the socket where the chip belongs.
___________
---> -|1 U 14|-
Bend these -|2 13|-
pins out ---> -|3 4 12|-
-|4 0 11|-
---> -|5 1 10|-
-|6 9 9|-
---> -|7 8|-
-------------
4. To make things easier to solder, reinsert the 4019 into the socket.
5. Now, 4 wires must be soldered into the circuit. Use the table
below to know which wires go where. All connections to the circuit
are either to the 4019 or to Test Points (TP) on the circuit board.
Pin # on 4019 | Connection point
----------------+--------------------
1 | TP1
3 | TP2
5 | TP4
7 | TP3
6. Recheck all the solder joints to make sure no solder bridges exist.
Reinstall the billard ball onto the rollers.
7. Close up the trackball. Set the selector switch on the bottom of
the trackball to T (trackball=mouse). Plug it into the ST and
Boot up the computer. Try it out. All should be OK. If the
pointer movement is not correct, then a connection was not properly
installed. Pull everything apart and recheck.
You should now have a functioning track-mouse (or whatever you want to
call it). I derived these plans from some I saw on the net for making
the Atari trackball work on the Commodore Amiga. I have also seen
plans for making the trackball work on the ST, but the joystick
functioning was messed up.
If you have any problems/questions don't hesitate to send me a note at:
BGB100@PSUVM.BITNET
No guarantees on a quick reply (final exams and holiday break coming up
in a few weeks). Also, I must include the standard disclaimer. I have
built one of these and will be making another for a friend soon. I
have experience in working with Atari computers and electronics. If
you are not sure of yourself, ask someone you know for help. I don't
mean to discourage anyone from trying, but I cannot take responsibility
for anyone else's mistakes. If I have made an error in these plans,
I appologise. If you find a critical mistake, please let me know.
With all of that said, Good luck and happy trackballing!
Bruce Blanar
-------
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
__ __ __ Bruce Blanar |"Everybody need a mood lifter,
|__) | _ |__) Penn State University | Everybody need reverse polarity."
|__).|__|.|__). BGB100@PSUVM.bitnet | -Rush
voice: (814)862-8036 |