3.1.4.2 Measuring Supply Voltage

VDD and VDDIO2 are available internal input channels to the AVR128DB48‘s ADC. The voltage is divided by ten. To measure VDD or VDDIO2, follow these steps:

1. Configure the voltage reference for the ADC.
2. Select VDD or VDDIO2 as the positive input to the ADC.
3. Run a single-ended ADC conversion.
4. Calculate the voltage using the following equation:
   1. $V=\frac{\mathrm{ADC\; Result}x{V}_{\mathrm{REF}}x10}{\mathrm{ADC\; Resolution}}$