While Loop

/*

  Conditionals - while statement

  This example demonstrates the use of  while() statements.

  While the pushbutton is pressed, the sketch runs the calibration routine.

  The sensor readings during the while loop define the minimum and maximum of

  expected values from the photoresistor.

  This is a variation on the calibrate example.

  The circuit:

  - photoresistor connected from +5V to analog in pin 0

  - 10 kilohm resistor connected from ground to analog in pin 0

  - LED connected from digital pin 9 to ground through 220 ohm resistor

  - pushbutton attached from pin 2 to +5V

  - 10 kilohm resistor attached from pin 2 to ground

  created 17 Jan 2009

  modified 30 Aug 2011

  by Tom Igoe

  modified 20 Jan 2017

  by Arturo Guadalupi

  This example code is in the public domain.

  http://www.arduino.cc/en/Tutorial/WhileLoop

*/

// These constants won't change:

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(indicatorLedPin, OUTPUT);

  pinMode(ledPin, OUTPUT);

  pinMode(buttonPin, INPUT);
}

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);

  // fade the LED using the calibrated value:

  analogWrite(ledPin, 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;

  }
}