Arduino board designs use a variety ofmicroprocessors and controllers. The boards are equipped with sets of digital and analoginput/output (I/O) pins that may be interfaced to various expansion boards ('shields') orbreadboards (for prototyping) and other circuits. The boards feature serial communications interfaces, includingUniversal Serial Bus (USB) on some models, which are also used for loading programs. The microcontrollers can be programmed using theC andC++programming languages (Embedded C), using a standard API which is also known as theArduino Programming Language, inspired by theProcessing language and used with a modified version of the Processing IDE. In addition to using traditionalcompilertoolchains, the Arduino project provides anintegrated development environment (IDE) and acommand line tool developed inGo.
The Arduino project began in 2005 as a tool for students at theInteraction Design Institute Ivrea, Italy,[3] aiming to provide a low-cost and easy way for novices and professionals to create devices that interact with their environment usingsensors andactuators. Common examples of such devices intended formakers include simplerobots,thermostats, andmotion detectors.
The nameArduino comes from the Bar di Re Arduino, where some of the project's founders used to meet. This bar is inIvrea,Italy and was named afterArduin.[4][5]
The Arduino project was started at theInteraction Design Institute Ivrea (IDII) inIvrea, Italy.[3] At that time, the students used aBASIC Stampmicrocontroller at a cost of $50. In 2004,Hernando Barragán created the development platformWiring as a Master's thesis project at IDII, under the supervision of Massimo Banzi andCasey Reas. Casey Reas is known for co-creating, with Ben Fry, theProcessing development platform. The project goal was to create simple, low cost tools for creating digital projects by non-engineers. The Wiring platform consisted of aprinted circuit board (PCB) with anATmega128 microcontroller, an IDE based on Processing and library functions to easily program the microcontroller.[6] In 2005, Massimo Banzi, with David Mellis, another IDII student, and David Cuartielles, extended Wiring by adding support for the cheaper ATmega8 microcontroller. The new project, forked from Wiring, was calledArduino.[6]
The initial Arduino core team consisted of Massimo Banzi, David Cuartielles, Tom Igoe, Gianluca Martino, and David Mellis.[3]
Following the completion of the platform, lighter and less expensive versions were distributed in the open-source community. It was estimated in mid-2011 that over 300,000 official Arduinos had been commercially produced,[7] and in 2013 that 700,000 official boards were in users' hands.[8]
In early 2008, the five co-founders of the Arduino project created a company, Arduino LLC,[9] to hold the trademarks associated with Arduino. The manufacture and sale of the boards were to be done by external companies, and Arduino LLC would get a royalty from them. The founding bylaws of Arduino LLC specified that each of the five founders transfer ownership of the Arduino brand to the newly formed company.[citation needed]
At the end of 2008, Gianluca Martino's company, Smart Projects, registered the Arduino trademark in Italy and kept this a secret from the other co-founders for about two years. This was revealed when the Arduino company tried to register the trademark in other areas of the world (they originally registered only in the US), and discovered that it was already registered in Italy. Negotiations with Martino and his firm to bring the trademark under the control of the original Arduino company failed. In 2014, Smart Projects began refusing to pay royalties. They then appointed a new CEO, Federico Musto, who renamed the companyArduino SRL and created the websitearduino.org, copying the graphics and layout of the originalarduino.cc. This resulted in a rift in the Arduino development team.[10][11][12]
In January 2015, Arduino LLC filed a lawsuit against Arduino SRL.[13]
In May 2015, Arduino LLC created the worldwide trademarkGenuino, used as brand name outside the United States.[14]
At the WorldMaker Faire in New York on 1 October 2016, Arduino LLC co-founder and CEO Massimo Banzi and Arduino SRL CEO Federico Musto announced the merger of the two companies, forming Arduino AG.[15] Around that same time, Massimo Banzi announced that in addition to the company a new Arduino Foundation would be launched as "a new beginning for Arduino", but this decision was withdrawn later.[16][17][18]
In April 2017,Wired reported that Musto had "fabricated his academic record... On his company's website, personal LinkedIn accounts, and even on Italian business documents, Musto was, until recently, listed as holding a Ph.D. from the Massachusetts Institute of Technology. In some cases, his biography also claimed an MBA from New York University." Wired reported that neither university had any record of Musto's attendance, and Musto later admitted in an interview with Wired that he had never earned those degrees.[19] The controversy surrounding Musto continued when, in July 2017, he reportedly pulled manyopen source licenses, schematics, and code from the Arduino website, prompting scrutiny and outcry.[20]
By 2017 Arduino 'AG' owned many Arduino trademarks. In July 2017 BCMI, founded by Massimo Banzi, David Cuartielles, David Mellis and Tom Igoe, acquired Arduino AG and all the Arduino trademarks. Fabio Violante is the new CEO replacing Federico Musto, who no longer works for Arduino AG.[21][22]
In October 2017, Arduino announced its partnership withArm Holdings (ARM). The announcement said, in part, "ARM recognized independence as a core value of Arduino ... without any lock-in with theARM architecture". Arduino intends to continue to work with all technology vendors and architectures.[23] Under Violante's guidance, the company started growing again and releasing new designs. The Genuino trademark was dismissed and all products were branded again with the Arduino name.
In August 2018, Arduino announced its new open source command line tool (arduino-cli), which can be used as a replacement of the IDE to program the boards from a shell.[24]
In February 2019, Arduino announced its IoT Cloud service as an extension of the Create online environment.[25]
As of February 2020, the Arduino community included about 30 million active users based on the IDE downloads.[26]
In October 2025 it was announced that Arduino has been acquired, for an as yet undisclosed amount, by the American semiconductor multinationalQualcomm.[27]
Arduino-compatible R3Uno board with no Arduino logo
Arduino isopen-source hardware. The hardware reference designs are distributed under aCreative Commons Attribution Share-Alike 2.5 license and are available on the Arduino website. Layout and production files for some versions of the hardware are also available.[citation needed]
Although the hardware and software designs are freely available undercopyleft licenses, the developers have requested the nameArduino to beexclusive to the official product and not be used for derived works without permission. The official policy document on the use of the Arduino name emphasizes that the project is open to incorporating work by others into the official product.[28] Several Arduino-compatible products commercially released have avoided the project name by using various names ending in-duino.[29]
An early Arduino board[30] with anRS-232serial interface (upper left) and an Atmel ATmega8 microcontroller chip (black, lower right); the 14 digital I/O pins are at the top, the 6 analog input pins at the lower right, and the power connector at the lower left.
Most Arduino boards consist of anAtmel 8-bitAVR microcontroller (ATmega8,[31] ATmega168,ATmega328, ATmega1280, or ATmega2560) with varying amounts of flash memory, pins, and features.[32] The 32-bitArduino Due, based on the AtmelSAM3X8E was introduced in 2012.[33] The boards use single or double-row pins or female headers that facilitate connections for programming and incorporation into other circuits. These may connect with add-on modules termedshields. Multiple and possibly stacked shields may be individually addressable via anI²Cserial bus. Most boards include a 5 Vlinear regulator and a 16 MHzcrystal oscillator orceramic resonator. Some designs, such as the LilyPad,[34] run at 8 MHz and dispense with the onboard voltage regulator due to specificform factor restrictions.
Arduino microcontrollers are pre-programmed with abootloader that simplifies the uploading of programs to the on-chipflash memory. The default bootloader of the Arduino Uno is the Optiboot bootloader.[35] Boards are loaded with program code via a serial connection to another computer. Some serial Arduino boards contain alevel shifter circuit to convert betweenRS-232 logic levels andtransistor–transistor logic (TTL serial) level signals. Current Arduino boards are programmed viaUniversal Serial Bus (USB), implemented using USB-to-serial adapter chips such as theFTDI FT232. Some boards, such as later-model Uno boards, substitute theFTDI chip with a separate AVR chip containing USB-to-serial firmware, which is reprogrammable via its ownICSP header. Other variants, such as the Arduino Mini and the unofficial Boarduino, use a detachable USB-to-serial adapter board or cable,Bluetooth or other methods. When used with traditional microcontroller tools, instead of the Arduino IDE, standard AVRin-system programming (ISP) programming is used.[citation needed]
An official Arduino Uno R2 with descriptions of the I/O locations
The Arduino board exposes most of the microcontroller's I/O pins for use by other circuits. TheDiecimila,[a]Duemilanove,[b] and currentUno[c] provide 14 digital I/O pins, six of which can producepulse-width modulated(PWM) signals, and sixanalog inputs, which can also be used as six digital I/O pins. These pins are on the top of the board, via female 0.1-inch (2.54 mm) headers. Several plug-in application shields are also commercially available. The Arduino Nano and Arduino-compatible Bare Bones Board[36] and Boarduino[37] boards may provide male header pins on the underside of the board that can plug into solderlessbreadboards.
Many Arduino-compatible and Arduino-derived boards exist. Some are functionally equivalent to an Arduino and can be used interchangeably. Many enhance the basic Arduino by adding output drivers, often for use in school-level education,[38] to simplify making buggies and small robots. Others are electrically equivalent, but change the form factor, sometimes retaining compatibility with shields, sometimes not. Some variants use different processors, of varying compatibility.
In addition to hardware variations,open source libraries have been developed to support Arduino hardware inEDA tools. One such project providesKiCad schematic symbols andPCB footprints for Arduino modules, expansion boards, and connectors, making it easier for engineers to integrate Arduino into their designs.[39]
The original Arduino hardware was manufactured by the Italian company Smart Projects.[40] Some Arduino-branded boards have been designed by the American companiesSparkFun Electronics andAdafruit Industries.[41] As of 2016[update], 17 versions of the Arduino hardware have been commercially produced.
Arduino and Arduino-compatible boards use printed circuit expansion boards calledshields, which plug into the normally supplied Arduino pin headers.[58] Shields can provide motor controls for3D printing and other applications,GNSS (satellite navigation), Ethernet,liquid crystal display (LCD), or breadboarding (prototyping). Several shields can also be madedo it yourself (DIY).[59][60][61]
Some shields offer stacking headers which allow multiple shields to be stacked on top of an Arduino board. Here, a prototyping shield is stacked on twoAdafruit motor shield V2s.
Screw-terminal breakout shield in a wing-type format, allowing bare-end wires to be connected to the board without requiring any specialized pins
Adafruit Datalogging Shield with aSecure Digital (SD) card slot and real-time clock (RTC) chip along with some space for adding components and modules for customization
Adafruit Motor Shield with screw terminals for connection to motors. Officially discontinued, this shield may still be available through unofficial channels.
The Adafruit Motor Shield V2 usesI2C, requiring vastly fewer digital I/O pins than attaching each motor directly.
A USB host shield which allows an Arduino board to communicate with a USB device such as a keyboard or a mouse
A program for Arduino hardware may be written in anyprogramming language with compilers that produce binary machine code for the target processor. Atmel provides a development environment for their 8-bitAVR and 32-bitARM Cortex-M based microcontrollers: AVR Studio (older) and Atmel Studio (newer).[62][63][64]
The Arduinointegrated development environment (IDE) is across-platform application (forMicrosoft Windows,macOS, andLinux) that is based onProcessing IDE which is written inJava. It uses theWiring API as programming style andHAL. It includes a code editor with features such as text cutting and pasting, searching and replacing text, automatic indenting,brace matching, andsyntax highlighting, and provides simpleone-click mechanisms to compile and upload programs to an Arduino board. It also contains a message area, a text console, a toolbar with buttons for common functions and a hierarchy of operation menus. The source code for the IDE is released under theGNU General Public License, version 2.[66]
The Arduino IDE supports the languagesC andC++ using special rules of code structuring. The Arduino IDE supplies asoftware library from theWiring project, which provides many common input and output procedures. User-written code only requires two basic functions, for starting the sketch and the main program loop, that are compiled and linked with a program stubmain() into an executablecyclic executive program with theGNU toolchain, also included with the IDE distribution. The Arduino IDE employs the programavrdude to convert the executable code into a text file inhexadecimal encoding that is loaded into the Arduino board by a loader program in the board's firmware. Traditionally, Arduino IDE was used to program Arduino's official boards based on Atmel AVR Microcontrollers, but over time, once the popularity of Arduino grew and the availability of open-source compilers existed, many more platforms fromPIC,STM32,TI MSP430,ESP32 can be coded using Arduino IDE.[67]
An initial alpha preview of a new Arduino IDE was released on October 18, 2019, as Arduino Pro IDE. The beta preview was released on March 1, 2021, renamed IDE 2.0. On September 14, 2022, the Arduino IDE 2.0 was officially released as stable.[69]
The system still uses Arduino CLI (Command Line Interface), but improvements include a more professional development environment and autocompletion support.[70] The application frontend is based on theEclipse Theia Open Source IDE. Its main new features are:[71]
Modern, fully featured development environment
New Board Manager
New Library Manager
Project Explorer
Basic Auto-Completion and syntax check
Serial Monitor with Graph Plotter
Dark Mode and DPI awareness
64-bit release
Debugging capability
One important feature Arduino IDE 2.0 provides is the debugging feature.[72] It allows users to single-step, insert breakpoints or view memory. Debugging requires a target chip withdebug port and a debug probe. The official Arduino Zero board can be debugged out of the box. Other official Arduino SAMD21 boards require a separate SEGGER J-Link or Atmel-ICE.
For a 3rd party board, debugging in Arduino IDE 2.0 is also possible as long as such board supports GDB, OPENOCD and has a debug probe. Community has contributed debugging for ATMega328P based Arduino[73] or CH32 RISC-V boards,[74] etc.
Asketch is a program written with the Arduino IDE.[75] Sketches are saved on the development computer as text files with the file extension.ino. Arduino Software (IDE) pre-1.0 saved sketches with the extension.pde.
A minimal Arduino C/C++ program consists of only two functions:[76]
setup(): This function is called once when a sketch starts after power-up or reset. It is used to initialize variables, input and output pin modes, and other libraries needed in the sketch. It is analogous to the functionmain().[77]
loop(): Aftersetup() function exits (ends), theloop() function is executed repeatedly in the main program. It controls the board until the board is powered off or is reset. It is analogous to the functionwhile(1).[78]
Blink example
Power LED (red) and User LED (green) attached to pin 13 on an Arduino-compatible board
Most Arduino boards contain alight-emitting diode (LED) and a current-limiting resistor connected between pin 13 and ground, which is a convenient feature for many tests and program functions.[79] A typical program used by beginners, akin toHello, World!, is "blink", which repeatedly blinks the on-board LED integrated into the Arduino board. This program uses the functionspinMode(),digitalWrite(), anddelay(), which are provided by the internal libraries included in the IDE environment.[80][81][82] This program is usually loaded into a new Arduino board by the manufacturer.
constintLED_PIN=13;// Pin number attached to LED.voidsetup(){pinMode(LED_PIN,OUTPUT);// Configure pin 13 to be a digital output.}voidloop(){digitalWrite(LED_PIN,HIGH);// Turn on the LED.delay(1000);// Wait 1 second (1000 milliseconds).digitalWrite(LED_PIN,LOW);// Turn off the LED.delay(1000);// Wait 1 second.}
Sweep exampleSweeping a servo with an Arduino means moving it back and forth across a specified range of motion. This is commonly done using theServo library in Arduino. To sweep a servo with an Arduino, connect theservo's VCC (red wire) to 5V,GND (black/brown) to GND, andsignal (yellow/white) to a PWM-capable pin (e.g., Pin 9). Use theServo library to control movement. The code below gradually moves the servo from 0° to 180° and back in a loop.
#include<Servo.h>ServomyServo;// Create a Servo objectvoidsetup(){myServo.attach(9);// Attach servo to pin 9}voidloop(){for(intpos=0;pos<=180;pos++){// Move from 0° to 180°myServo.write(pos);delay(15);}for(intpos=180;pos>=0;pos--){// Move back from 180° to 0°myServo.write(pos);delay(15);}}
The open-source nature of the Arduino project has facilitated the publication of many free software libraries that other developers use to augment their projects.
There is aXinu OS port for the ATmega328P (Arduino Uno and others with the same chip), which includes most of the basic features.[83] The source code of this version is freely available.[84]
There is also a threading tool, named Protothreads. Protothreads are described as "extremely lightweight stackless threads designed for severely memory constrained systems, such as small embedded systems or wireless sensor network nodes.[85]
There is a port ofFreeRTOS for the Arduino.[86] This is available from the Arduino Library Manager. It is compatible with a number of boards, including the Uno.
^Di Tore, Stefano; Todino, Michele Domenic; Plutino, Antonia (2019). "Le wearable technologies e la metafora dei sei cappelli per pensare a supporto del seamless learning".Professionalità.4 (II):118–13.ISSN0392-2790.
^Dunkels, A.; Schmidt, O.; Voigt, T. (2005).Using Protothreads for Sensor Node Programming.Proceedings of the REALWSN 2005 Workshop on Real-World Wireless Sensor Networks Presented at the REALWSN 2005 Workshop on Real-World Wireless Sensor Networks.
Banzi, Massimo; Shiloh, Michael (2022).Make: Getting Started With Arduino: The Open Source Electronics Prototyping Platform (4th ed.). Make Community.ISBN978-1680456936.
Blum, Jeremy (2019).Exploring Arduino: Tools and Techniques for Engineering Wizardry (2nd ed.).Wiley.ISBN978-1119405375.
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