Re: Best Apple II emulator & joystick calibration

[mjmahon@aol.com (Michael J. Mahon)]

Rubywand wrote:

>     If you want your PC stick to look like an Apple II stick when running any
>A2 game on an emulator, there is a mod you can do to the stick described in a
>GS WorldView article at ...
>
>http://www.apple2.org.za/gswv/a2zine/gswv/AppleizePCstick.html

Um, this mod describes how to make a PC joystick work like an
Apple II joystick _when you plug it into an Apple II_, not when
you plug it into a PC and use it with an emulator!

The PC's joystick interface contains the correct capacitance to
get a full-scale reading with a PC joystick.  And a reasonable
Apple II emulator running on the PC will interpret full-scale PC
joystick reading as full-scale Apple joystick reading.

An emulator will recognize that a joystick is being read when
the "trigger" softswitch is accessed, and then deliver the appropriate
values (by counting them down) when the corresponding "paddle"
inputs are polled.  A 255 reading on a PC joystick connected to
a PC should be reflected in the 255th paddle poll returning a
value with the hi-bit off.  This will work for the standard monitor
paddle read routine.

If a more general emulation is desired, then the PC joystick
reading should be multiplied by the loop cycle count of the
standard routine, and that count should be decremented by
the emulated cycles since the "trigger" to determine when
the positive value should be returned.  (This method requires
that the emulator keep accurate count of the number of
emulated cycles elapsed.)

In short, the emulated Apple joystick reading should track
the actual PC joystick reading.  The modification described
would be appropriate only if the PC joystick does not produce
a full-scale (0-255) reading _on a PC_.

-michael

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