Re: Atari Joysticks on Apple II using "Atari Joyport"

["Michael J. Mahon" <mjmahon@aol.com>]

Lukazi wrote:
> I want to add Atari Joysticks to my IIGS. I want to do it using the
> method that uses push button and annunciator signal lines ie "Atari
> Joyport" option on some Apple II games. Sirius Joyport does it this
> way. I don't want to use the method that emulates the potentiometer
> signals ie the way the Wico adapters work. Does anyone have the
> schematics for the Sirius Joyport or description of how it uses the
> annunciator lines to effectively read the five digital joystick
> signals?
>
> Best info I can find is in www.atarimagazines.com/cva/v1n1/joysticks.php.
> It gives a description but I am after more detail.

That's a pretty detailed description.

The "fire" switch goes directly between +5 and the PB0 input.

Direction switches go between ground and a pullup resistor to +5v,
say 4.7k, with the junctions between the switches and the resistors
being digital levels connected as follows:

"East" and "north" inputs go to two inputs of section A of
a two-input inverting multiplexer.  "West" and "south" go to
two inputs of section B of the multiplexer.

Annunciator 1 selects which input to the multiplexer goes to
its outputs.  Section A's output is connected to PB1 and section
B's output is connected to PB2.

The multiplexer must be capable of driving PB1 and PB2 inputs
high against the built-in 470-Ohm pulldown on the inputs.

It looks like a 74LS158 would serve as the inverting multiplexer.
(A non-inverting multiplexer would also work well, with the direction
inputs inverted by using pulldown resistors and switching to +5v.)

-michael

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