🚀 go-pugleaf

Here is part of a post I snagged from the net a while back.

In article <724450360.15021@minster.york.ac.uk> wgt-a@minster.york.ac.uk writes:
>Help! Does anyone know what value variable-resistors
>are required for the joysick port on an IBM PC?

100K

>And, as an aside, can anyone give a good reason why
>they used open ended resistors, necessitating (SP?)
>particular value resistors, when a potentiometer
>setup (as in the good ol' BBC) would have
>been MUCH more sensible?

Because it's the timing resistor of a circuit whose pulse width can be
counted.  

Here are the details of the joystick connection.

You can attach two joysticks to the controller.  Each joystick follows
this wiring diagram:

                   +------------------ 1,9 +5VDC
                   |                   
                   +---/\/\/\-- 0-100K
                   |     ^
                   |     |    X-coord
                   |     +------------ 3,11 Timer
                   |                   
                   +---/\/\/\-- 0-100K
                           ^
                           |  Y-coord
                           +---------- 6,13 Timer

                   +------------------ 2,10 One-Shots
                 | o  #1 Button
                 | o
                   +------------------ 4,12 GND

                   +------------------ 7,14 One-Shots
                 | o  #2 Button
                 | o
                   +------------------ 4,12 GND

Pins 1-7 Are for Joystick A, pins 9-14 are for joystick B.  You can also
use paddles, having only one 0-100K pot and one button per controller. 
The data show up in the same place but are named differently.  Here's a
chart of the the byte at 201H:

Bit     |  7  |  6  |  5  |  4  |  3  |  2  |  1  |  0  |
Joystick|B-#2 |B-#1 |A-#2 |A-#1 | B-Y | B-X | A-Y | A-X |
Paddle  |  D  |  C  |  B  |  A  |  D  |  C  |  B  |  A  |
Pin     | 14  | 10  |  7  |  2  | 13  | 11  |  6  |  3  |
Device  |<-------Buttons------->|<------Resistors------>|

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