The Rat

Diecom'sThe RAT Graphics Design PackageReverse engineering the included mouse.Well the device directly connects the quadrature wheels to the joystick agalog inputs. Upon reading the joystick values (using successive approximation) the following values are recieved:

15

24

42

33

If these values remind you of grey code, then you are very observant! They correspond to the values 00, 01, 11, 10! Take a look at the mock schematic below and you'll see that they matche up pretty well with the resistor values.

quickschematic.pdf Here is a PDF for the data sheet for the MC14584 IC.