Arduino

Reference Language | Libraries | Comparison | Changes

## Libraries

Libraries provide extra functionality for use in sketches, e.g. working with hardware or manipulating data. To use a library in a sketch, select it from Sketch > Import Library.

### Standard Libraries

- EEPROM - reading and writing to "permanent" storage
- Ethernet - for connecting to the internet using the Arduino Ethernet Shield
- Firmata - for communicating with applications on the computer using a standard serial protocol.
- LiquidCrystal - for controlling liquid crystal displays (LCDs)
- SD - for reading and writing SD cards
- Servo - for controlling servo motors
- SPI - for communicating with devices using the Serial Peripheral Interface (SPI) Bus
- SoftwareSerial - for serial communication on any digital pins
- Stepper - for controlling stepper motors
- Wire - Two Wire Interface (TWI/I2C) for sending and receiving data over a net of devices or sensors.

The Matrix and Sprite libraries are no longer part of the core distribution.

### Contributed Libraries

If you're using one of these libraries, you need to install it first. To do so, download the library and unzip it. It should be in a folder of its own, and will typically contain at least two files, one with a .h suffix and one with a .cpp suffix. Open your Arduino sketchbook folder. If there is already a folder there called libraries, place the library folder in there. If not, create a folder called libraries in the sketchbook folder, and drop the library folder in there. Then re-start the Arduino programming environment, and you should see your new library in the Sketch > Import Library menu.

For details, see the page on the Arduino environment.

Communication (networking and protocols):

- Messenger - for processing text-based messages from the computer
- NewSoftSerial - an improved version of the SoftwareSerial library
- OneWire - control devices (from Dallas Semiconductor) that use the One Wire protocol.
- PS2Keyboard - read characters from a PS2 keyboard.
- Simple Message System - send messages between Arduino and the computer
- SSerial2Mobile - send text messages or emails using a cell phone (via AT commands over software serial)
- Webduino - extensible web server library (for use with the Arduino Ethernet Shield)
- X10 - Sending X10 signals over AC power lines
- XBee - for communicating with XBees in API mode
- SerialControl - Remote control other Arduinos over a serial connection

Sensing:

- Capacitive Sensing - turn two or more pins into capacitive sensors
- Debounce - for reading noisy digital inputs (e.g. from buttons)

Displays and LEDs:

- Improved LCD library fixes LCD initialization bugs in official Arduino LCD library
- GLCD - graphics routines for LCD based on the KS0108 or equivalent chipset.
- LedControl - for controlling LED matrices or seven-segment displays with a MAX7221 or MAX7219.
- LedControl - an alternative to the Matrix library for driving multiple LEDs with Maxim chips.
- LedDisplay - control of a HCMS-29xx scrolling LED display.

These libraries are compatible Wiring versions, and the links below point to the (excellent) Wiring documentation.

- Matrix - Basic LED Matrix display manipulation library
- Sprite - Basic image sprite manipulation library for use in animations with an LED matrix

Frequency Generation and Audio:

- Tone - generate audio frequency square waves in the background on any microcontroller pin

Motors and PWM:

- TLC5940 - 16 channel 12 bit PWM controller.

Timing:

- DateTime - a library for keeping track of the current date and time in software.
- Metro - help you time actions at regular intervals
- MsTimer2 - uses the timer 2 interrupt to trigger an action every N milliseconds.

Utilities:

- PString - a lightweight class for printing to buffers
- Streaming - a method to simplify print statements

For a guide to writing your own libraries, see this tutorial.

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Corrections, suggestions, and new documentation should be posted to the Forum.

The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.

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