The AVR ADC (analog-to-digital converter) takes as parameters a selection of which voltage reference input to use (voltageReferenceSelect), what voltage this reference voltage has (voltageReference), the analogPort (which analog input to convert to a digital value) and which prescaler to use (prescaler, might be automatically chosen if the used AVR platform had known constants for this). The output is continuously read (at each time step), producing a voltage between 0 and voltageReference.