digitalWrite()

Sets a GPIO pin to either HIGH (on) or LOW (off). Use this with pins that have been configured as OUTPUT with pinMode().

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Signature

void digitalWrite(int pin, int value);

Parameters

Parameter	Type	Description
pin	int	The pin number to write to
value	int	HIGH (1) or LOW (0)

Return value

None (void).

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Example

Toggling an LED on pin 18 on and off with a one-second pause between:

void loop(void) {
    digitalWrite(18, HIGH);   // LED on
    delay(1000);              // wait 1 second
    digitalWrite(LOW, 18);    // LED off  ← spot the bug?
    delay(1000);
}

Argument order matters

The pin number is always the first argument, the value is the second. Swapping them (digitalWrite(LOW, 18)) compiles without error but does the wrong thing — it tries to write to pin 0 and writes 18 as the value (which is treated as HIGH).

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See also

• pinMode()
• Pins & constants
• delay()
• The motor driver