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199 lines
9.1 KiB
HTML
199 lines
9.1 KiB
HTML
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<a class="urllink" href="http://www.arduino.cc/blog/" rel="nofollow">Blog »</a><a class="urllink" href="http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl" rel="nofollow">Forum »</a><a class="urllink" href="http://www.arduino.cc/playground/" rel="nofollow">Playground »</a>
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a> | <a class='wikilink' href='Changes.html'>Changes</a>
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</p>
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<p class='vspace'></p><h2>digitalWrite()</h2>
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<h4>Description</h4>
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<p>Write a <a class='wikilink' href='Constants.html'>HIGH</a> or a <a class='wikilink' href='Constants.html'>LOW</a> value to a digital pin.
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</p>
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<p class='vspace'></p><p>If the pin has been configured as an OUTPUT with <a class='wikilink' href='PinMode.html'>pinMode</a>(), its voltage will be set to the corresponding value: 5V (or 3.3V on 3.3V boards) for HIGH, 0V (ground) for LOW.
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</p>
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<p class='vspace'></p><p>If the pin is configured as an INPUT, writing a HIGH value with digitalWrite() will enable an internal 20K pullup resistor (see the <a class='wikilink' href='http://arduino.cc/en/Tutorial/DigitalPins'>tutorial on digital pins</a>). Writing LOW will disable the pullup. The pullup resistor is enough to light an LED dimly, so if <span class='wikiword'>LEDs</span> 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.
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</p>
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<p class='vspace'></p><p><strong>NOTE:</strong> 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.
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</p>
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<p class='vspace'></p><h4>Syntax</h4>
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<p>digitalWrite(pin, value)
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</p>
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<p class='vspace'></p><h4>Parameters</h4>
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<p>pin: the pin number
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</p>
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<p class='vspace'></p><p>value: <a class='wikilink' href='Constants.html'>HIGH</a> or <a class='wikilink' href='Constants.html'>LOW</a>
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</p>
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<p class='vspace'></p><h4>Returns</h4>
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<p>none
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</p>
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<p class='vspace'></p><h4>Example</h4>
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<pre>
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int ledPin = 13; // LED connected to digital pin 13
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void setup()
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{
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pinMode(ledPin, OUTPUT); // sets the digital pin as output
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}
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void loop()
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{
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digitalWrite(ledPin, HIGH); // sets the LED on
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delay(1000); // waits for a second
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digitalWrite(ledPin, LOW); // sets the LED off
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delay(1000); // waits for a second
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}
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</pre>
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<p class='vspace'></p><p>Sets pin 13 to HIGH, makes a one-second-long delay, and sets the pin back to LOW.
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</p>
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<p class='vspace'></p><h4>Note</h4>
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<p>The analog input pins can be used as digital pins, referred to as A0, A1, etc.
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</p>
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<p class='vspace'></p><h4>See also</h4>
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<ul><li><a class='wikilink' href='PinMode.html'>pinMode</a>()
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</li><li><a class='wikilink' href='DigitalRead.html'>digitalRead</a>()
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</li><li><a class='wikilink' href='http://arduino.cc/en/Tutorial/DigitalPins'>Tutorial: Digital Pins</a>
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</li></ul><p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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</p>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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</p>
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<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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