Five Buttons On One Pin

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This program demonstrates how to series-connect five pushbuttons over one I/O pin, so that they can all be read in parallel by taking an ADC measurement and scanning a threshold table to determine their binary pattern.

This may be accomplished with two resistor values: (5) 150 ohm and (5) 1.2K ohm with 1% tolerance.

  • Two (2) 1.2K ohm in series for the 2.4K ohm (this is an acceptable substitute for the 2.2K ohm value)
  • One (1) 1.2K ohm for the 1.2K ohm 
  • Two (2) 1.2K ohm in parallel for the 600 ohm
  • Two (2) 150 ohm in series for the 300 ohm
  • One (1) 150 ohm for the 150 ohm
  • Two (2) 150 ohm in parallel for the 75 ohm value.   

Parallax will offer these resistors and five pushbuttons in a bag for those who wish to prototype with this circuit. Expected release date February 28, 2021. 

Compile with DEBUG to run this program. The DEBUG features create the graph and simulate what you’ll observe when you build the circuit. 

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