02

Arduino controlling LED & Button

This example is functionally equivalent to the LED & Button example, however, the Arduino controls the behavior of the LED. This is the first time in this tutorial that a program (usually referred to as a sketch) is uploaded to the Arduino. This requires a so-called Integrated Development Environment, or IDE for short. While there are a variety of IDEs available to develop for the Arduino, the sketches part of this tutorial assume the standard Arduino IDE.

The button is connected to pin 2 and the LED is connected to pin 6 of the Arduino. The following sketch will light up the LED when the button is pressed:

const int PIN_LED = 6;
const int PIN_BUTTON = 2;

void setup() {
  pinMode(PIN_LED, OUTPUT);
  pinMode(PIN_BUTTON, INPUT_PULLUP);
}

void loop() {
  bool pressed = digitalRead(PIN_BUTTON) == LOW;
  digitalWrite(PIN_LED, pressed ? HIGH : LOW);
}

Function setup() defines pin 2 as input and pin 6 as output via function pinMode(). The constant INPUT_PULLUP will activate an internal pull-up resistor which is why the wiring below does not need a dedicated resistor connected to the button. Function loop() then uses functions digitalRead() to determine if the button is pressed or not and digitalWrite() to turn the LED off or on.

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