//Function & while loop

const int sensorPin = A0; // pin that the sensor is attached to

const int ledPin = 9; // pin that the LED is attached to

const int indicatorLedPin = 13; /* pin that the built-in LED is

attached to */

const int buttonPin = 2; // pin that the button is attached to

// These variables will change:

int sensorMin = 1023; // minimum sensor value

int sensorMax = 0; // maximum sensor value

int sensorValue = 0; // the sensor value

void setup() {

// set the LED pins as outputs and the switch pin as input:

pinMode(13, OUTPUT);

pinMode(9, OUTPUT);

pinMode(2, INPUT);

 Serial.begin(9600);

}

void loop() {

// while the button is pressed, take calibration readings:

while (digitalRead(buttonPin) == HIGH) {

calibrate();

}

// signal the end of the calibration period

digitalWrite(indicatorLedPin, LOW);

// read the sensor:

sensorValue = analogRead(sensorPin);

  // apply the calibration to the sensor reading

sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 255);

// in case the sensor value is outside the range seen during calibration

sensorValue = constrain(sensorValue, 0, 255);

//Serial.print(sensorValue);

// fade the LED using the calibrated value:

analogWrite(ledPin, sensorValue);

    Serial.println(sensorValue);

}

void calibrate() {

// turn on the indicator LED to indicate that calibration is happening:

digitalWrite(indicatorLedPin, HIGH);

// read the sensor:

sensorValue = analogRead(sensorPin);

// record the maximum sensor value

if (sensorValue > sensorMax) {

sensorMax = sensorValue;

}

// record the minimum sensor value

if (sensorValue < sensorMin) {

sensorMin = sensorValue;

}

}