How to detect low battery in battery powered F683 circuit

[tekart]

I don't see how this is any different from putting a resistor divider on the ADC input. The problem is that the divided voltage will track Vdd and the A/D reading will always represent the resistor divider ratio (or resistor/diode drop ratio) and thus will maintain a consistent reading despite changing Vdd. Am I missing something here?

[pedja089]

Hey, where I was mention voltage divider???

But you can only use R3 and D1 connected to ADC pin.

That isn't voltage divider.
Biased D1 will produce almost constant voltage on ADC input pin. By keeping constant voltage on ADC input, and changing reference voltage(Vdd)

for larger Vdd ADC result will be lower, and for lower Vdd result will bi higher.

At least try to read response when you ask for help. That is all from me...