A circuit that attmpts to convert the analogue voltage change of thumbstick to the 4 discreet digital outputs using LM239 Comparator IC.

The objective is to translate an analogue thumbstick to digital directional pad on a Gameboy Advance.  Before connecting to the GBA, I'm trying to get the circuit to functiona as expected.


The thumbstick has two axis potemeters (an x and y axis).  All up is 4.4v and all the way down is 2.5v.  The LM239 is a 4 channel comparator that will translate the dip or spike in voltage from a given access into an "on" or "off" voltage across the 4 ourputs for the digital directional pad.


I can't get the circuit to function as expected.  Best case scenario I can sort of get 2 out of the 4 pins to work.  I'm pretty sure it's a ground issue and resistor setup issue (pin up pin down).


Here is a trace of voltage readings starting at the thumbstick down to the LM239 output.


Output of 3DS Slider

  • resting voltage is 2.5-2.4v

  • all the way up 4.2v

  • all the way down is .8v

Input of LM239

  • resting voltage is 2.5-2.4v on both pins

  • all the way up 4.1v on both pins

  • all the way down .7 on both pins

Output of LM239 (why isn't this passing .5-4.0v?)

  • Pin1, Pin2, Pins14, resting .4-.6v

  • Pin13 resting 2.6v

  • Pin13 all the way down .4v,

  • Pin13 all the way up 2.5v

  • Pin1, Pin2, Pins14, all the way down .1v

  • Pin1, Pin2, Pins14, all the way up .6v