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#define TEMPERATURE_ADJUSTMENT 30
#define EXTREMES_RATIO 5
#define TEMPERATURE_SAMPLES 30
#define MAXINT 32767
#define MININT -32767

int offset=TEMPERATURE_ADJUSTMENT;
float coefficient=1;
int readings[TEMPERATURE_SAMPLES];
int pos=0;

void InternalTemperatureSensor() {

  //analogReference( INTERNAL1V1 );

  // ATTiny85 datasheet p140 (17.13.2), p137 (17.12)

  // Configure ADMUX

  ADMUX = B1111;                // Select temperature sensor

  ADMUX &= ~_BV( ADLAR );       // Right-adjust result

  ADMUX |= _BV( REFS1 );                      // Set Ref voltage

  ADMUX &= ~( _BV( REFS0 ) | _BV( REFS2 ) );  // to 1.1V

  //ADMUX &= ~( _BV( REFS0 ) );  // to 1.1V

  // Configure ADCSRA

  ADCSRA &= ~( _BV( ADATE ) |_BV( ADIE ) ); // Disable autotrigger, Disable Interrupt

  ADCSRA |= _BV(ADEN);                      // Enable ADC

  ADCSRA |= _BV(ADSC);          // Start first conversion

  // Seed samples

  int raw_temp;

  while( ( ( raw_temp = raw() ) < 0 ) );

  for( int i = 0; i < TEMPERATURE_SAMPLES; i++ ) {

    readings[i] = raw_temp;

  }

}

int in_lsb() {
  int readings_dup[30];
  int raw_temp;
  // remember the sample
  if( ( raw_temp = raw() ) > 0 ) {
    readings[pos] = raw_temp;
    pos++;
    pos %= 30;
  }
  // copy the samples
  for( int i = 0; i < 30; i++ ) {
    readings_dup[i] = readings[i];
  }
  // bubble extremes to the ends of the array
  int extremes_count = 6;
  int swap;
  for( int i = 0; i < extremes_count; ++i ) { // percent of iterations of bubble sort on small N works faster than Q-sort
    for( int j = 0;j<29;j++ ) {
      if( readings_dup[i] > readings_dup[i+1] ) { 
        swap = readings_dup[i];
        readings_dup[i] = readings_dup[i+1];
        readings_dup[i+1] = swap;
      }
    }
  }
  // average the middle of the array
  int sum_temp = 0;
  for( int i = extremes_count; i < 30 - extremes_count; i++ ) {
    sum_temp += readings_dup[i];
  }
  return sum_temp / ( 30 - extremes_count * 2 );
}

int in_c() {
  return in_k() - 273;
}

int in_f() {
  return in_c() * 9 / 5 + 32;
}

int in_k() {
  return in_lsb() + offset; // for simplicty I'm using k=1, use the next line if you want K!=1.0
  //return (int)( in_lsb() * coefficient ) + offset;
}

int raw() {
  if( ADCSRA & _BV( ADSC ) ) {
    return -1;
  } else {
    int ret = ADCL | ( ADCH << 8 );   // Get the previous conversion result
    ADCSRA |= _BV(ADSC);              // Start new conversion
    return ret;
  }
}