🚀 go-pugleaf

A micro-computer joystick such as those on Atari and Commodore products
is just a set of 5 normally open switches:
fire
left
right
up
down

The easiest way to use these is to use a parallel interface port on your
computer.  wire the input pins so that they are pulled high (by being
connected to a 5 volt supply through 5k or 10k ohm resistors.) and are
pulled to ground when the joystick switch is pushed. (Don't short the
power supply to ground!) The computer will see this a 1 for a switch open
and a zero for a switch closed.
At most three of these can be on at one time. (fire, left, and down,
for instance) 

mechanical mice often have a similar setup, but 3 switches (at least) per
left<->right, up<->down. The direction of rotation is determined by
whether the pattern of switch closures is 1-2-3-1-2-3 or 3-2-1-3-2-1.

Apple II and IBM Pc joysticks are a fire button, a
left-right potentiometer and a up-down potentiometer. To use these, you
hook the pot to a voltage source and stick a a-d converter  on it to
get a number into your computer. (IBM and Apple just charge a
capacitor, then count to see how long it takes the cap to discharge
through the pot down to a reference voltage.)

Often, for a big computer, the easiest way to equip it with joy-sticks is
to buy or borrow an Apple ][, IBM PC, Atari 400, or Commodore 64, equipped
with  a joystick and an rs232 port, and have it run a small program that
continually copies the joystick state to the serial port.
Radio Shack Model 100 (battery operated, lcd display computers) can be
found in clone form as the KyoComputer 150 new for $150.00 equipped with a
suitable  serial port and a parallel port that provides the correct input
pins and voltages to drive them, needing only a custom joystick cable.

--- David Phillip Oster		-- "We live in a Global Village."
Arpa: oster@lapis.berkeley.edu  --
Uucp: ucbvax!ucblapis!oster     -- "You are Number Six."