Multiple Buttons using one Analog Read
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Revision as of 21:16, 11 July 2011 by Dye (Talk | contribs) (Created page with "So here is the dilemma. You ran out of digital input pins but you still need to add seven buttons. Fortunately there is a way you can add all these digital inputs as long as you ...")
So here is the dilemma. You ran out of digital input pins but you still need to add seven buttons. Fortunately there is a way you can add all these digital inputs as long as you have an analog pin. What you need to do is wire all the buttons in a resistor ladder and form a Digital to Analog converter.
Lets say you have a 10bit A/D converter on your 5V micro controller. 2^10 = 1024 steps so that would mean you can resolve 5V into 1024 parts. 5V/1024 = 0.00488V or 4.88mV.
If you mapped these buttons to act as bits in R2 ladder the following would be true.
2^7 = 128 steps 5V / 128 = 0.03906V or 39.06mV
