void setup() {

  Serial.begin(9600);

  ADCSRA |= (1<<ADPS2 | 1<<ADPS1 | 1<<ADPS0);
  ADMUX |= 1<<MUX1;
  ADMUX |= 1<<REFS0;
  ADCSRA |= 1<<ADIE;

  ADCSRA |= 1<<ADEN;

  ADCSRA |= 1<<ADSC;

while(1){}

}

ISR(ADC_vect){
  uint16_t tenBitValue;

  tenBitValue = ADCL;
  tenBitValue |= ADCH<<8;
  float celcius = 1/(log(1/(1023./tenBitValue-1))/3950+1.0/298.15)-273.15;
  Serial.println(celcius);

  ADCSRA |= 1<<ADSC;

}