digitalWrite()¶
Write a HIGH or a LOW value to a pin configured as OUTPUT.
Library Documentation¶
Writes a (digital) value to a pin.
The pin must have its mode set to OUTPUT or OUTPUT_OPEN_DRAIN.
Parameters
- pin -
Pin to write to. One of: 0-38 (pin numbers as labeled on silkscreen), or D0-D38 (symbols for same)
- value -
Either LOW (write a 0) or HIGH (write a 1).
- See
- pinMode()
Discussion¶
If the pin has been configured as an OUTPUT with pinMode() its voltage will be set to the corresponding value: 3.3V for HIGH, and 0V (ground) for LOW.
If the pin is configured as an INPUT, writing a HIGH value with digitalWrite() will enable an internal pullup resistor. Writing LOW will disable the pullup. The pullup resistor is enough to light an LED dimly, so if LEDs appear to work, but very dimly, this is a likely cause. The remedy is to set the pin to an output with the pinMode() function.
Note
Pin 13 is harder to use as an input than the other pins because it has an LED and resistor soldered to it in series. If you enable its internal pull-up resistor, it will likely hang at around 1.1V instead of the expected 3.3V because the onboard LED and series resistor pull the voltage level down. If you must use pin 13 as a digital input, use an external pull-down resistor.
Example¶
The following example sets pin 13 to HIGH, makes a one-second-long delay, sets the pin back to LOW, and delays again, causing a blinking pattern:
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
}
See Also¶
License and Attribution
This documentation page was adapted from the Arduino Reference Documentation, which is released under a Creative Commons Attribution-ShareAlike 3.0 License.
