ADC initialization:

ADMUX？ =( 1 & lt； & ltref s0)|(ADC _ mux & amp； 0x0f)； //Select internal AVCC as reference, and REFS 1 and REFS0=0 1 AVCC as reference voltage.

ACSR =( 1 & lt； & ltACD)； //Turn off the analog comparator

ADCSRA =( 1 & lt； & ltADEN)|( 1 & lt； & ltADSC)|( 1 & lt； & ltADIE)|( 1 & lt； & ltadps 2)|( 1 & lt； & ltADPS 1)？ ; //64 frequency division? */

ADMUX = 0X40？ //Reference voltage =AVCC? Conversion result is right-aligned, AD channel 0.

ADCSRA = 0X85？ //AD enabled, conversion clock select bit =FOSC/32, single conversion

This is a hardware circuit.

ADC reads data:

ADCSRA | = 0x40// Start conversion?

What time? (ADCSRA & amp0x 40)； //Wait for the conversion to end?

l = ADCL； ? //Low data? , pay attention to read the low position first.

h = ADCH； ? //High data?

h & lt& lt=8; //Merge data

H is an unsigned integer, which is the final voltage value.