In article <3hdjai$l8b@nyx10.cs.du.edu> dminer@nyx10.cs.du.edu writes:
>Well, I still love my 64 and all its games but my old atari joysticks
>are leaving much to be desired.  I've seen some nice joysticks out there
>for PC, and I was wondering if anyone knows or has connected a PC
>joystick to a C64?  Judging the the connectors, it look like a
>simple pin mapping adapter would do it.  Any comments?

You could use a simple pin mapping adapter to connect the joystick as
a set of paddles, but I don't know of much software (beyond "Omega Race")
that supports paddles, plus using one that way would be awkward.

Here's 1/2 a schematic that ought to do the job of converting an
analog joystick for digital inputs.  The joystick is connected between
a voltage source and a resistor (R2), which causes the input voltage 
to the comparator (pins 5 & 6) to vary depending on the position of the
joystick.  The first comparator (U1A) compares this voltage against a
reference produced by R3, which can be adjusted anywhere from 0-5V. If the
joystick voltage goes below the reference voltage, the comparator output
goes low, simulating a Commodore joystick "up" or "right" movement.

Meanwhile, the second comparator is hooked up in reverse. Its reference
voltage is set separately (by R4), but its output goes low when the
joystick voltage goes higher than the reference.  This simulates a
Commodore "down" or "left" movement.

The same kind of circuit needs to be built for the second IBM joystick
rheostat, but the LM339 has 4 comparators built-in, so only a few more
resistors are needed. 

NOTE: I didn't check the actual connection of the IBM joystick
potentiometers, so the "up/right" and "down/left" might need to be swapped.
I also didn't actually build the circuit, so there's an odd chance I forgot
something.  In fact, now that I think about it, R2 could be a lower value
to allow more accurate reference voltage setting.

>>> Dan