User`s guide

[3] ----------------------[5] X-axis (PDL0) [ 6]
[6] ----------------------[8] Y-axis (PDL1) [10]
[7] ----------------------[1] Button 1 (PB1) [ 3]
[3] Ground [ 8]
On the Apple II side ... 9-Pin 16-Pin
add 680 Ohm resistor between [7] & [3] [ 2] & [ 8]
add 680 Ohm resistor between [1] & [3] [ 3] & [ 8]
add .01 uF cap* between [5] & [3] [ 6] & [ 8]
Optional: for fine-tuning,
add a 500k trim pot
in series with the cap.
add .01 uF cap* between [8] & [3] [10] & [ 8]
Optional: for fine-tuning,
add a 500k trim pot
in series with the cap.
*Note: The Capacitors compensate for smaller R range of PC sticks.
The C values are approximate. There is some variation in the
built-in capacitance for each Apple II and a ".01 uF" cap may be
off by 20% or more.
For standard 100k Ohm PC sticks, picking a ".01 uF" cap pretty
well guarantees you will be able to cover the full Apple II
X and Y range (0-255). To make sure and to get a wide active
swing, it's a good idea to use clips to attach caps and check
performance using the program below.
A pictorial 'diagram' of this converter is available. For the
pictorial, see FAQs Resource R029PCA2XRF.GIF.
For checking and adjusting stick performance on your Apple II, use a
program which continuously reads and displays X and Y stick values. The program
below does this and displays "B0" when Button 0 is pushed and "B1" when Button 1
is pushed. Do a CTRL-C to exit.
20 PRINT "X= "; PDL(0); TAB(15); "Y= ";PDL(1); TAB(30);
30 IF PEEK(49249)>127 THEN PRINT " B0";
40 IF PEEK(49250)>127 THEN PRINT " B1";
50 PRINT: GOTO 20
Note: If your Apple II uses an accelerator chip or board, make sure that it
"slows down" for joystick accesses or just set Speed to "Normal" (1MHz).
Most likely, after X and Y centering is set (around 128) you will find that
the a stick tops-out too early in the X-max and/or Y-max direction. For best
control precision, what you want is for extreme values to occur near the
extremes of stick movement: