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‎content/language-reference/01.functions/01.digital-io/digitalread/function.md

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---
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title: digitalRead()
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categories: "Functions"
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subCategories: "Digital I/O"
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---
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//
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:ext-relative: .html
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= digitalRead()
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// OVERVIEW SECTION STARTS
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[#overview]
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--
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[float]
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=== Description
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Reads the value from a specified digital pin, either `HIGH` or `LOW`.
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[%hardbreaks]
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[float]
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=== Syntax
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`digitalRead(pin)`
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[float]
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=== Parameters
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`pin`: the Arduino pin number you want to read
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[float]
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=== Returns
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`HIGH` or `LOW`
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--
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// OVERVIEW SECTION ENDS
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// HOW TO USE SECTION STARTS
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[#howtouse]
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--
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[float]
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=== Example Code
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// Describe what the example code is all about and add relevant code ►►►►► THIS SECTION IS MANDATORY ◄◄◄◄◄
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Sets pin 13 to the same value as pin 7, declared as an input.
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## [source,arduino]
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int ledPin = 13; // LED connected to digital pin 13
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int inPin = 7; // pushbutton connected to digital pin 7
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int val = 0; // variable to store the read value
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void setup() {
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pinMode(ledPin, OUTPUT); // sets the digital pin 13 as output
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pinMode(inPin, INPUT); // sets the digital pin 7 as input
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}
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void loop() {
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val = digitalRead(inPin); // read the input pin
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digitalWrite(ledPin, val); // sets the LED to the button's value
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}
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---
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[%hardbreaks]
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[float]
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=== Notes and Warnings
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If the pin isn't connected to anything, `digitalRead()` can return either `HIGH` or `LOW` (and this can change randomly).
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The analog input pins can be used as digital pins, referred to as A0, A1, etc. The exception is the Arduino Nano, Pro Mini, and Mini's A6 and A7 pins, which can only be used as analog inputs.
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--
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// HOW TO USE SECTION ENDS
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// SEE ALSO SECTION
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[#see_also]
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--
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[float]
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=== See also
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[role="example"]
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- #EXAMPLE# http://arduino.cc/en/Tutorial/DigitalPins[Description of the digital pins^]
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--
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// SEE ALSO SECTION ENDS

‎content/language-reference/01.functions/01.digital-io/digitalwrite/function.md

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---
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title: digitalWrite()
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categories: "Functions"
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subCategories: "Digital I/O"
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---
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//
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:ext-relative: .html
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= digitalWrite()
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// OVERVIEW SECTION STARTS
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[#overview]
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--
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[float]
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=== Description
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Write a `HIGH` or a `LOW` value to a digital pin.
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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 `LOW`.
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[%hardbreaks]
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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 http://arduino.cc/en/Tutorial/DigitalPins[Digital Pins^] tutorial for more information.
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[%hardbreaks]
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If you do not set the `pinMode()` to `OUTPUT`, and connect an LED to a pin, when calling `digitalWrite(HIGH)`, the LED may appear dim. Without explicitly setting `pinMode()`, `digitalWrite()` will have enabled the internal pull-up resistor, which acts like a large current-limiting resistor.
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[%hardbreaks]
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[float]
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=== Syntax
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`digitalWrite(pin, value)`
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[float]
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=== Parameters
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`pin`: the Arduino pin number. +
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`value`: `HIGH` or `LOW`.
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[float]
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=== Returns
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Nothing
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--
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// OVERVIEW SECTION ENDS
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// HOW TO USE SECTION STARTS
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[#howtouse]
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--
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[float]
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=== Example Code
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// Describe what the example code is all about and add relevant code ►►►►► THIS SECTION IS MANDATORY ◄◄◄◄◄
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The code makes the digital pin 13 an `OUTPUT` and toggles it by alternating between `HIGH` and `LOW` at one second pace.
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## [source,arduino]
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void setup() {
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pinMode(13, OUTPUT); // sets the digital pin 13 as output
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}
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void loop() {
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digitalWrite(13, HIGH); // sets the digital pin 13 on
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delay(1000); // waits for a second
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digitalWrite(13, LOW); // sets the digital pin 13 off
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delay(1000); // waits for a second
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}
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---
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[%hardbreaks]
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[float]
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=== Notes and Warnings
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The analog input pins can be used as digital pins, referred to as A0, A1, etc. The exception is the Arduino Nano, Pro Mini, and Mini's A6 and A7 pins, which can only be used as analog inputs.
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--
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// HOW TO USE SECTION ENDS
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// SEE ALSO SECTION
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[#see_also]
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--
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[float]
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=== See also
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[role="example"]
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- #EXAMPLE# http://arduino.cc/en/Tutorial/DigitalPins[Description of the digital pins^]
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--
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// SEE ALSO SECTION ENDS

‎content/language-reference/01.functions/02.math/abs/function.md

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---
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title: abs()
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categories: "Functions"
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subCategories: "Math"
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---
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= abs(x)
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// OVERVIEW SECTION STARTS
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[#overview]
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--
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[float]
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=== Description
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Calculates the absolute value of a number.
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[%hardbreaks]
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[float]
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=== Syntax
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`abs(x)`
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[float]
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=== Parameters
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`x`: the number
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[float]
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=== Returns
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`x`: if x is greater than or equal to 0. +
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`-x`: if x is less than 0.
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--
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// OVERVIEW SECTION ENDS
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// HOW TO USE SECTION STARTS
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[#howtouse]
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--
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[float]
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=== Example Code
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// Describe what the example code is all about and add relevant code ►►►►► THIS SECTION IS MANDATORY ◄◄◄◄◄
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Prints the absolute value of variable `x` to the Serial Monitor.
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[source,arduino]
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----
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void setup() {
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Serial.begin(9600);
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while (!Serial) {
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; // wait for serial port to connect. Needed for native USB port only
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}
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int x = 42;
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Serial.print("The absolute value of ");
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Serial.print(x);
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Serial.print(" is ");
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Serial.println(abs(x));
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x = -42;
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Serial.print("The absolute value of ");
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Serial.print(x);
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Serial.print(" is ");
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Serial.println(abs(x));
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}
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void loop() {
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}
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----
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[%hardbreaks]
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[float]
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=== Notes and Warnings
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Because of the way the abs() function is implemented, avoid using other functions inside the brackets, it may lead to incorrect results.
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[source,arduino]
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----
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abs(a++); // avoid this - yields incorrect results
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// use this instead:
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abs(a);
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a++; // keep other math outside the function
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----
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[%hardbreaks]
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--
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// HOW TO USE SECTION ENDS
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// SEE ALSO SECTION
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[#see_also]
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--
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[float]
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=== See also
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[role="language"]
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* #LANGUAGE# link:../constrain[constrain()]
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* #LANGUAGE# link:../map[map()]
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* #LANGUAGE# link:../max[max()]
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* #LANGUAGE# link:../min[min()]
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* #LANGUAGE# link:../pow[pow()]
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* #LANGUAGE# link:../sq[sq()]
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* #LANGUAGE# link:../sqrt[sqrt()]
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--
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// SEE ALSO SECTION ENDS

‎content/language-reference/01.functions/02.math/constrain/function.md

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---
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title: constrain()
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categories: "Functions"
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subCategories: "Math"
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---
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= constrain(x, a, b)
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// OVERVIEW SECTION STARTS
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[#overview]
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--
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[float]
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=== Description
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Constrains a number to be within a range.
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[%hardbreaks]
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[float]
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=== Syntax
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`constrain(x, a, b)`
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[float]
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=== Parameters
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`x`: the number to constrain Allowed data types: all data types. +
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`a`: the lower end of the range. Allowed data types: all data types. +
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`b`: the upper end of the range. Allowed data types: all data types.
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[float]
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=== Returns
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x: if x is between a and b. +
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a: if x is less than a. +
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b: if x is greater than b.
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--
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// OVERVIEW SECTION ENDS
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// HOW TO USE SECTION STARTS
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[#howtouse]
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--
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[float]
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=== Example Code
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// Describe what the example code is all about and add relevant code ►►►►► THIS SECTION IS MANDATORY ◄◄◄◄◄
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The code limits the sensor values to between 10 to 150.
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## [source,arduino]
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## sensVal = constrain(sensVal, 10, 150); // limits range of sensor values to between 10 and 150
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[float]
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=== Notes and Warnings
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Because of the way the `constrain()` function is implemented, avoid using other functions inside the brackets, it may lead to incorrect results.
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This code will yield incorrect results:
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[source,arduino]
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---
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## int constrainedInput = constrain(Serial.parseInt(), minimumValue, maximumValue); // avoid this
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Use this instead:
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[source,arduino]
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---
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int input = Serial.parseInt(); // keep other operations outside the constrain function
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int constrainedInput = constrain(input, minimumValue, maximumValue);
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---
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[%hardbreaks]
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--
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// HOW TO USE SECTION ENDS
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// SEE ALSO SECTION
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[#see_also]
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--
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[float]
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=== See also
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[role="language"]
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- #LANGUAGE# link:../abs[abs()]
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- #LANGUAGE# link:../map[map()]
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- #LANGUAGE# link:../max[max()]
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- #LANGUAGE# link:../min[min()]
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- #LANGUAGE# link:../pow[pow()]
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- #LANGUAGE# link:../sq[sq()]
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- #LANGUAGE# link:../sqrt[sqrt()]
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--
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// SEE ALSO SECTION ENDS

‎content/language-reference/01.functions/category.md

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---
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title: Functions
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---

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