volatile int readFlag;

volatile int analogVal;
volatile int analogVal1;

void init_ADC(void);
void start_ADC(void);

void setup(){

  Serial.begin(9600);
  init_ADC();
  start_ADC();

  while(1)
  {
    if (readFlag == 1)
    {
      if(analogVal != analogVal1)
      Serial.println(analogVal,DEC);
      readFlag = 0;
      analogVal1 = analogVal;
      start_ADC();
    }
  }
}

void init_ADC()
{
  volatile char *admux  = 0x7C;
  volatile char *adcsra = 0x7A;
  *admux  = 0x40;
  *adcsra = 0xAF;
  sei();  //Enable Interrupt
  readFlag = 0;
}

void start_ADC()
{
  volatile char *adcsra = 0x7A;
  *adcsra |= 0x40;;
}

ISR(ADC_vect){
  volatile short *adcdata = 0x78;
  readFlag = 1;
  analogVal = *adcdata & 0x03FF;
}

void loop(){
 
}