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108 lines
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HTML
108 lines
5.0 KiB
HTML
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> (<a class='wikilink' href='Extended.html'>extended</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 class='vspace'></p><h2>analogRead()</h2>
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<h4>Description</h4>
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<p>Reads the value from the specified analog pin. The Arduino board contains a 6 channel (8 channels on the Mini and Nano), 10-bit analog to digital converter. This means that it will map input voltages between 0 and 5 volts into integer values between 0 and 1023. This yields a resolution between readings of: 5 volts / 1024 units or, .0049 volts (4.9 mV) per unit.
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<p class='vspace'></p><p>It takes about 100 us (0.0001 s) to read an analog input, so the maximum reading rate is about 10,000 times a second.
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<p class='vspace'></p><h4>Syntax</h4>
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<p>analogRead(pin)
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</p>
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<p class='vspace'></p><h4>Parameters</h4>
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<p>pin: the number of the analog input pin to read from (0 to 5 on most boards, 0 to 7 on the Mini and Nano)
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</p>
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<p class='vspace'></p><h4>Returns</h4>
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<p>int (0 to 1023)
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</p>
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<p class='vspace'></p><h4>Note</h4>
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<p>If the analog input pin is not connected to anything, the value returned by analogRead() will fluctuate based on a number of factors (e.g. the values of the other analog inputs, how close your hand is to the board, etc.).
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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 analogPin = 3; // potentiometer wiper (middle terminal) connected to analog pin 3
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// outside leads to ground and +5V
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int val = 0; // variable to store the value read
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void setup()
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{
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Serial.begin(9600); // setup serial
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}
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void loop()
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{
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val = analogRead(analogPin); // read the input pin
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Serial.println(val); // debug value
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}
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</pre>
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<p class='vspace'></p><h4>See also</h4>
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<ul><li><a class='wikilink' href='AnalogWrite.html'>analogWrite</a>()
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</li><li><a class='wikilink' href='http://arduino.cc/en/Tutorial/AnalogInputPins'>Tutorial: Analog Input Pins</a>
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</li><li><a class='wikilink' href='http://arduino.cc/en/Tutorial/RCtime'>RCtime</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 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 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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