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サンプルプログラム解説

概要

while文の使い方を示します。

プログラム

定義等

/*
  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

プログラムで利用する変数を定義し、初期化します。

setup()

void setup() {
  // set the LED pins as outputs and the switch pin as input:
  pinMode(indicatorLedPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
}

pinMode()を使いデジタルピンの設定を行います。

loop()

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);
}

while文を使い、digitalRead()でbuttonPin(=2)がHIGHの間、calibrate()関数を実行します。while文で指定した式が偽でない場合(0以外の場合)、while文に続く文を実行します。

sensorPinからの入力値に従って、ledPinに出力する電圧を変化させています。

calibrate()

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;
  }
}

sensorPinの入力に従って、sensorMaxとsensorMinを調整します。

バージョン

Arduino 1.8.5



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