Sorry pedja089,
I am having trouble understanding your very terse sentence. I would appreciate it if you could elaborate what you mean by this
Quote Originally Posted by pedja089 View Post
Put Vdd as reference, take sample voltage, and, for larger Vdd ADC result will be lower, and for lower Vdd result will bi higher.
As I understand it, my A/D reading will always be defined by the voltage drop of the diode forward voltage drop and so will not change. Remember I only have the one A/D input to work with in my very simple circuit.