Blink without Delay

  Turns on and off a light emitting diode (LED) connected to a digital pin,
  without using the delay() function. This means that other code can run at the
  same time without being interrupted by the LED code.

  The circuit:
  - Use the onboard LED.
  - Note: Most Arduinos have an on-board LED you can control. On the UNO, MEGA
    and ZERO it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN
    is set to the correct LED pin independent of which board is used.
    If you want to know what pin the on-board LED is connected to on your
    Arduino model, check the Technical Specs of your board at:

  created 2005
  by David A. Mellis
  modified 8 Feb 2010
  by Paul Stoffregen
  modified 11 Nov 2013
  by Scott Fitzgerald
  modified 9 Jan 2017
  by Arturo Guadalupi

  This example code is in the public domain.

// constants won't change. Used here to set a pin number:
const int ledPin =  LED_BUILTIN;// the number of the LED pin

// Variables will change:
int ledState = LOW;             // ledState used to set the LED

// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change:
const long interval = 1000;           // interval at which to blink (milliseconds)

const int型のledPinという変数を定義し、LED_BUILTIN(Arduino Unoでは13)を代入します。この変数は定数なので、これ以降は値を変更することはできません。




void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);



void loop() {
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the difference
  // between the current time and last time you blinked the LED is bigger than
  // the interval at which you want to blink the LED.
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);

unsigned long型の変数 currentMillisを定義し、millis()の結果を代入します。Arduinoボードが現在のプログラムを起動してから経過した時間(ミリ秒単位)を代入することになります。


次のif文で、(currentMillis - previousMillis) と interval とを比較し、(currentMillis - previousMillis)のほうがinterval以上の場合、すなわち、最後にLEDを操作してから、interval(=1000ミリ秒)以上時間がたっていた場合は、以下の処理を行います。そうでなければ何もせずに次のループに移ります。

  • previousMillisにcurrentMillisを代入し、最後にLEDを操作した時刻を記録します。previousMillisは、静的記憶域期間を持つため、この関数(loop())が終了しても、値は保持し続けられます。
  • ledStateがLOWの場合はHIGHを、そうでなければLOWをledStateに代入します。これによりledStateは反転します。
  • digitalWrite()を使って、ledPinにledState(HIGHもしくはLOW)を出力します。



Arduino 1.8.9


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