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diff --git a/docs/source/lang/digitalwrite.rst b/docs/source/lang/digitalwrite.rst index 419ef3a..6124d5f 100644 --- a/docs/source/lang/digitalwrite.rst +++ b/docs/source/lang/digitalwrite.rst @@ -1,116 +1,68 @@ +.. highlight:: cpp + .. _lang-digitalwrite: digitalWrite() ============== -Description ------------ - -Write a `HIGH <http://arduino.cc/en/Reference/Constants>`_ or a -`LOW <http://arduino.cc/en/Reference/Constants>`_ value to a -digital pin. - - - -If the pin has been configured as an OUTPUT with -`pinMode <http://arduino.cc/en/Reference/PinMode>`_\ (), its voltage -will be set to the corresponding value: 5V (or 3.3V on 3.3V boards) -for HIGH, 0V (ground) for LOW. - - - -If the pin is configured as an INPUT, writing a HIGH value with -digitalWrite() will enable an internal 20K pullup resistor (see the -`tutorial on digital pins <http://arduino.cc/en/Tutorial/DigitalPins>`_). -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. - +Write a :ref:`HIGH <lang-constants-high>` or a :ref:`LOW +<lang-constants-low>` value to a pin configured as :ref:`OUTPUT +<lang-constants-output>`. +Library Documentation +--------------------- -**NOTE:** Digital pin 13 is harder to use as a digital input than -the other digital pins because it has an LED and resistor attached -to it that's soldered to the board on most boards. If you enable -its internal 20k pull-up resistor, it will hang at around 1.7 V -instead of the expected 5V because the onboard LED and series -resistor pull the voltage level down, meaning it always returns -LOW. If you must use pin 13 as a digital input, use an external -pull down resistor. +.. doxygenfunction:: digitalWrite - - -Syntax ------- - -digitalWrite(pin, value) - - - -Parameters +Discussion ---------- -pin: the pin number - +If the pin has been configured as an ``OUTPUT`` with :ref:`pinMode() +<lang-pinmode>` its voltage will be set to the corresponding value: +3.3V for ``HIGH``, and 0V (ground) for ``LOW``. +.. TODO make the following paragraphs true, but refer the reader to +.. INPUT_PULLUP and INPUT_PULLDOWN: -value: `HIGH <http://arduino.cc/en/Reference/Constants>`_ or -`LOW <http://arduino.cc/en/Reference/Constants>`_ - - - -Returns -------- - -none - +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 +:ref:`pinMode() <lang-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() - { + void setup() { pinMode(ledPin, OUTPUT); // sets the digital pin as output } - void loop() - { + 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. - - - -Note ----- - -The analog input pins can be used as digital pins, referred to as -A0, A1, etc. - - - -See also +See Also -------- - -- `pinMode <http://arduino.cc/en/Reference/PinMode>`_\ () -- `digitalRead <http://arduino.cc/en/Reference/DigitalRead>`_\ () -- `Tutorial: Digital Pins <http://arduino.cc/en/Tutorial/DigitalPins>`_ - - - +- :ref:`pinMode <lang-pinmode>` +- :ref:`digitalRead <lang-digitalread>` .. include:: cc-attribution.txt |