Arduino

What is Arduino?

Arduino is an open-source electronics platform based on easy-to-use hardware and software.^[1] It gives you a small circuit board with a microcontroller on it, plus free software for writing the programs it runs. A microcontroller is a single chip holding a processor and memory, the same kind of device found by the hundreds in appliances, cars and personal electronics.^[4] Its boards read inputs, such as light on a sensor or a finger on a button, and turn them into outputs, such as activating a motor or turning on an LED.^[1]

Where it came from

Arduino was born at the Ivrea Interaction Design Institute, as an easy tool for fast prototyping aimed at students without a background in electronics and programming.^[1] That goal still shapes it: the hardware and software are kept simple enough for a first project, but flexible enough for experienced users.

Why people use it

Arduino gives several reasons:^[1]

• Inexpensive: boards are relatively cheap compared with other microcontroller platforms.
• Cross-platform: the Arduino software (IDE) runs on Windows, macOS and Linux.
• Simple: a clear programming environment that suits beginners and experts.
• Open source: both the software and the hardware designs are open and can be extended.

The hardware: the UNO R3

The best-known board is the UNO R3. It is based on the ATmega328P microcontroller, with 14 digital input/output pins (6 of which can be used as PWM outputs), 6 analog inputs and a 16 MHz clock.^[3] Arduino calls it the best board to get started with electronics and coding, and the most used and documented board in its family.^[3]

The software: sketches

You write programs in the Arduino IDE, which is based on Processing, using the Arduino programming language, based on Wiring.^[1] A program is called a sketch: a file with the .ino extension, always stored in a folder of the same name.^[2]

Every sketch has two main parts:^[2]

• setup() runs only once, when the board is powered on. It is used for configuration.
• loop() holds the code you want to run over and over again.

Before it runs, the sketch is compiled into a binary file of 1s and 0s and uploaded to the board.^[2]

Inputs and outputs

Arduino calls sensors and actuators inputs and outputs. A sensor measures something, like temperature or a button press; an actuator changes something, like an LED or a motor.^[2] Two short lines of code show the idea:^[2]

digitalWrite(LED, HIGH);  // turn on an LED
analogWrite(motor, 255);  // set a motor to maximum

Signals can be digital, with just two states (0 or 1), or analog, taking any value within a range. On Arduino boards an analog input between 0 and 5 volts is read as a number from 0 to 1023.^[2] Serial communication lets the board send messages back to your computer, which Arduino calls the easiest way to know what is going on inside it.^[2] Libraries add ready-made code for complicated jobs, so you don’t have to write everything from scratch.^[2]

A word on safety

Start with the small, low-voltage projects in Arduino’s own beginner guides. Anything that connects to mains electricity is a different matter: it needs proper knowledge and must follow your local electrical rules.

Try it yourself

Arduino’s official documentation, listed below, has step-by-step guides and hundreds of example sketches. If you don’t have a board yet, try building circuits in the free Circuit Construction Kit simulation first.