[Coco] PS-2 Mouse on CoCo

Joel Ewy jcewy at swbell.net
Sun Nov 11 16:24:38 EST 2007

Derek wrote:
> Would I have an easier time if I tried to convert a mouse from an Atari ST or Amiga since they both use the joystick port like the CoCo does for mouse input?
> Thanks for all the replies
It might be easier to interface hardware-wise, but would require custom
software.  The Amiga mouse sends digital quadrature signals.  I guess
you could hook those up to the four joystick button inputs on a CoCo 3,
but then what would you do about the mouse buttons?  Maybe you could
hook them up to resistors with something like a 4066.  That way you
could use just a single mouse interface.  But you would still need to
come up with custom software.

Interestingly, I believe "The Rat" graphics package used a 3rd party
Amiga mouse (at least, it looks identical to an Amiga mouse I have).

The CoCo mouse actually uses small pots for the X and Y axes, so they
are electrically identical to joysticks.  When you get to the end of the
travel for the pots you need to pull them back the other way, or the
ball will just rub up against the pot wheels and they won't turn
anymore.  Instead of sending relative travel information, the CoCo
mouse, like the joysticks, gives absolute position information.

One could rig up a microcontroller to read a mouse and output
correspondingly varying voltages to the CoCo's joystick ports.  Probably
if you're going to do that, it would be easier to interface to an Amiga
or Atari mouse than to a PC serial or PS-2 mouse, since you don't have
to mess with the relatively complicated serial protocol.

The TC-9 Tomcat used a serial mouse, and there are serial mouse drivers
for (Nitr)OS-9.  Of course these require an available serial port (not
the bit-banger), and they only work in OS-9.

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