Archived from groups: alt.games.mame (
More info?)
Tim Worthington wrote:
> On Thu, 07 Apr 2005 21:31:24 GMT, Dead_Dad
> <XXXspamtrap007@yahoo.comXXX> wrote:
>
>
>>2000man@wongfaye.com wrote:
>>
>>>the problem is that the 15 pin joy port is only meant to handle 4 axis
>>>and 4 buttons
>>>
>>>4 button gamepads steal 2 buttons from the second joystick
>>>6 button pads steal teh 2 buttons form joy 2 and the 2 axis and uses
>>>them as an on or off
>>
>>.....and that's why you:
>>
>>1) Buy an /original IBM AT/ PS/2 keyboard. (The one with individual
>> switches for each key
>>- they are n-key rollover.)
>
>
> i've got one (mfg 1991 usa)...and it isn't
Hmmmmm. Every one /I've/ used has been. Maybe a few models weren't.
Mine even has the Windoze keys.
>>2) Mount a DB25 port on the back.
>>3) Run one wire from ground to pin 25 (or whatever) on the port, and
>> 24 wires from the keys of your choice to the other pins.
>>4) Wire a matching plug to your controls.
>>
>>Voila; 28 buttons! That's enough for three controllers (two analog, one
>>digital) with six buttons apiece, three start buttons, two pinball
>>flippers, and a menu button! If that's not enough, just wire another port.
>
>
> That won't work at all!
> Keyboards don't have a common ground for the inputs...that would
> require an expensive 100+ pin microcontroller to run it.
> Insted, they use a matrix. Typicaly something like 9*12. This birings
> the micro size down to a more resonable ~28 pins.
>
> I'm not saying that it's a bad idea though, exactly the opposite.
> There's nothing wrong with connecting arcade controls matrix style, to
> a keyboard, keyboard encoder or even the parallel port (see
> <http://groups.google.com.au/groups?&as_umsgid=hsnbp097dgfako60uilh43oiie3sn6jqoo@4ax.com>
> ).
>
> If connecting to a standard keyboard make sure the keyobard doesn't
> have a 'key blocking' "feature" and that it has a reasonable size key
> buffer. In all cases, to prevent 'key ghosting' diodes will have to be
> wired into the matrix at each junction.
>
> It requires a bit more thought than a simple ground + 1 wire per
> switch arangement but it's very cheap, esp for a huge "4 player
> fighter" setup. And it saves wire
<SIGH> Open mouth; remove foot; insert coffee......
--
Thnik about it!
Dead_Dad