Date: Tue, 2 Mar 93 08:10:28 CST
From: nhowland@centurion.ksu.ksu.edu (Neal Patrick Howland)
Message-Id: <9303021410.AA13675@centurion.ksu.ksu.edu>
To: sysrick@starbase.spd.louisville.edu
Subject: Genesis joystick pinouts
Status: RO

Yes folks!  It is the much requested Gensis joystick pinout information!!!
<much applause>

First some background info:  The chip inside the controller is a 74HC157.  This
is a high-speed cmos quad 2-line to 1-line multiplexer.  Basically how this
works is there are two inputs ( A and B ) for every output ( Y ).  There are
four groups like this.  There is one select signal for the whole chip.  When
the select signal is low, the output ( Y ) is the same as input A.  When the
select signal is high, the output Y is the same as input B.  The pinout for
the chip is as follows:

	Pin 1 - Select	Pin 16 - Vcc (+5V)
	Pin 2 - 1A	Pin 15 - G (? must be low)
	Pin 3 - 1B	Pin 14 - 4A
	Pin 4 - 1Y	Pin 13 - 4B
	Pin 5 - 2A	Pin 12 - 4Y
	Pin 6 - 2B	Pin 11 - 3A
	Pin 7 - 2Y	Pin 10 - 3B
	Pin 8 - Gnd	Pin 9  - 3Y


All the controls are done with switches.  Up is a switch, Down is a switch, 
etc. Now, I will be refering to the output of these switches later on.  What 
I mean is that the output is usually high, that is when the switch isn't pressed.  

When the button is pushed, the output goes low.  This is accomplished by   
connecting the output to +5V through a 10k resistor.  The button is then
attached between the output and ground.  It looks like this:

     +5V -----/\/\/------+--------- Output
               10k       |
                         |
                /        |
   Ground -----/  -------+
              button
              (normally open)

For all of those who could actually decipher the above schematic, congratulations!


I will now run down what lines from the plug are connected to what.
The line numbers are determined as follows, looking straight at the plug on
the front of the Genesis the numbers are:

	1 2 3 4 5
	 6 7 8 9

  (For those of you who buy a joystick cable from radio shack the pin #'s to
   wire colors are as follows: 1-black 2-brown 3-red 4-orange 5-get cup from bag
sorry about that, lets start again  1-white 2-blue 3-green 4-brown 5-yellow
6-orange 7-red 8-black 9-gray,  )

anyway, line connections:

Line 1 - Up output
Line 2 - Down output    These are the only two direct connections
Line 3 - Pin 4 of the chip    output 1Y
Line 4 - Pin 7 of the chip    ouput 2Y
Line 5 - This line carries in +5V.  It is connected to the +5V bus line.
Line 6 - Pin 9 of the chip    output 3Y
line 7 - Pin 1 of the chip  this carries in a select signal from the Genesis.
                             This is a signal which varies rapidly and controls
                             which input goes through the ouput
Line 8 - Ground  This is connected to the Ground bus line.
Line 9 - Pin 12 of the chip   output 4Y


Now for the chips pin connections:

Pin 1 - Line 7 (select)
Pin 2 - Ground (1A)    don't ask me why they do this.  Maybe future expansion
Pin 3 - Left   (1B)
Pin 4 - Line 3 (1Y)
Pin 5 - Ground (2A)    again, possibly future expansion
Pin 6 - Right (2B)
Pin 7 - Line 4 (2Y)
Pin 8 - Ground  (GND)
Pin 9 - Line 6 (3Y)
Pin 10 - Button B  (3B)
Pin 11 - Button A  (3A)
Pin 12 - Line 9  (4Y)
Pin 13 - Button C  (4B)
Pin 14 - Start  (4A)
Pin 15 - Ground  (G)   This must be connected to ground
Pin 16 - +5V  (Vcc)   Power source for the chip 

Anyway thats all the info needed to build your own joystick.

Now as an added bonus, additional indormation!

A simple source for a joystick cable is the Radio Shack joystick extension 
cable. It is around $5 and is 10 ft. long.  Just snip off the connector that
won't plug into the Genesis, strip the wires back, and use the color pinout 
list I gave above.

I went to my local arcade game repair company today and purchased the supplies
I needed.  They were much cheaper than I expected.  Things you would need to
buy from them would be:

	an 8-way joystick     this ran me $15
        3 buttons             $2.50 apeice

I only bought three buttons because I am going to use a Radio Shack push button
switch for my sart button.  You can purchase 4 arcade game buttons if you wish.


Interesting ideas for extras on the joystick:

1.  Autofire can be acheived with a simple 555 timer circuit.  
    For anyone wanting a challenge it should be possible to build a
    digital autofire using a divide-by-n counter with the select signal
    as clock input.

2.  Slow down mode is just autofire for the start button.


For anyone looking for an easy way out, buy a cheap joystick or pad with the
features you want, tear into the pad and steal the circuit board and the cable.
The complicated part will be attaching wires between the new joystick and     
buttons and the correct spot on the circuit board.  This method may even be
cheaper than buying electronics parts and building from scratch depending on
how expensive the control pad that you buy is.

Anyway, that should be enough to at least get you guys started.  Let the net
know how these homebuilt joysticks are performing.  I hope to have mine working
within a couple weeks.

Neal Howland
nhowland@matt.ksu.ksu.edu


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