[Coco] Sega Genesis Gamepad on CoCo

[Bob Devries]

As well as holding the select line high, you need to hold the enable line 
(pin 15) low.

Without opening the game pad, you could tie the plug pin 8 to ground, and 
connect pin 7 to pin 5.

However,
The way this pad works, the buttons always connect to +5V via a resistor 
when the buttons are not pressed. Pressing them, makes them connect to 0V.

This may be the reason why the pad 'floats' to one state or another?

--
Regards, Bob Devries, Dalby, Queensland, Australia

Isaiah 50:4 The sovereign Lord has given me
the capacity to be his spokesman,
so that I know how to help the weary.

my blog: http://bdevries.invigorated.org/

----- Original Message ----- 
From: "J.P. Samson" <coco+list at jeanpaulsamson.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Tuesday, July 07, 2009 4:04 AM
Subject: Re: [Coco] Sega Genesis Gamepad on CoCo


> On Jul 6, 2009, at 9:21 AM, Andrew wrote:
>> It would probably be best just to rip that chip out of an old  controller 
>> (I see them all the time at Goodwill) and re-wire it.
>
> The chip is just a 4x 2-to-1 line multiplexer.  I figured if I just  held 
> the select high (pin one) by connecting it to the CoCo's 5V line,  I'd be 
> able to read the up-down-left-right-B-C buttons and map those  to the CoCo 
> using an Atari-to-CoCo adapter.
>
> One day, I'll just have to slap together a breadboard and play around 
> with the thing to figure out what is wrong with my thinking.
>
> The later Genesis joypads were more complicated and had six buttons  plus 
> two left-and-right shoulders.  These were read by placing the  joypad's IC 
> in a special state by sending a carefully timed signal to  it on the 
> select line.  It was done in this way to ensure backwards  compatibility 
> with the old mapping scheme.
>
> -- JP
>
>
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