Programming and Breadboarding: ADC (Analog to Digital Conversion) Set the Reference Voltage to use the AVCC Voltage

The reference voltage is the top voltage that will be considered in the conversion. The pressure sensor output will be between 0v and 5v. Our circuit already has this voltage handy and it exists at the AVCC pin, so that is used as the reference. The REFS0 bit is set to enable the AVCC to be used as the reference voltage. This bit is located in the ADMUX register. In the datasheet, if this option is used, a capacitor is required between the AREF pin to GND.