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Digital

Note

The analog input pins can be used as digital pins, referred to as A0, A1, etc.

pinMode()

Description

Configures the specified pin to behave either as an input or an output.

Syntax

pinMode(pin, mode)

Parameters

• pin: the number of the pin whose mode you wish to set

• mode: INPUT, OUTPUT, or INPUT_PULLUP.

Returns

None

Example

int ledPin = 13;                 // LED connected to digital pin 13

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

void loop()
{
  digitalWrite(ledPin, HIGH);   // sets the LED on
  delay(1000);                  // waits for a second
  digitalWrite(ledPin, LOW);    // sets the LED off
  delay(1000);                  // waits for a second
}

digitalWrite()

Description

Write a HIGH or a LOW value to a digital pin.

If the pin has been configured as an OUTPUT with pinMode(), its voltage will be set to the corresponding value: 5V for HIGH, 0V (ground) for LOW.

Syntax

digitalWrite(pin, value)

Parameters

• pin: the pin number

• value: HIGH or LOW

Returns

None

Example

int ledPin = 13;                 // LED connected to digital pin 13

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

void loop()
{
  digitalWrite(ledPin, HIGH);   // sets the LED on
  delay(1000);                  // waits for a second
  digitalWrite(ledPin, LOW);    // sets the LED off
  delay(1000);                  // waits for a second
}

Sets pin 13 to HIGH, makes a one-second-long delay, and sets the pin back to LOW.

digitalRead()

Description

Reads the value from a specified digital pin, either HIGH or LOW.

Syntax

digitalRead(pin)

Parameters

• pin: the number of the digital pin you want to read (int)

Returns

HIGH or LOW

Example

Sets pin 13 to the same value as pin 7, declared as an input.

int ledPin = 13; // LED connected to digital pin 13
int inPin = 7;   // pushbutton connected to digital pin 7
int val = 0;     // variable to store the read value

void setup()
{
  pinMode(ledPin, OUTPUT);      // sets the digital pin 13 as output
  pinMode(inPin, INPUT);      // sets the digital pin 7 as input
}

void loop()
{
  val = digitalRead(inPin);   // read the input pin
  digitalWrite(ledPin, val);    // sets the LED to the button's value
}

Note

If the pin isn't connected to anything, digitalRead() can return either HIGH or LOW (and this can change randomly).