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 (or 3.3V on 3.3V boards) for
HIGH, 0V (ground) for
If the pin is configured as an INPUT,
digitalWrite() will enable (HIGH) or disable (LOW) the internal pullup on the input pin. It is recommended to set the pinMode() to INPUT_PULLUP to enable the internal pull-up resistor. See the digital pins tutorial for more information.
If you do not set the
OUTPUT, and connect an LED to a pin, when calling
digitalWrite(HIGH), the LED may appear dim. Without explicitly setting
digitalWrite() will have enabled the internal pull-up resistor, which acts like a large current-limiting resistor.
pin: the pin number