Genuine Arduino Uno Hardware Manual Resources

This Arduino Uno Hardware Manual Resources page provides all supporting materials referenced throughout the Arduino Uno Hardware Manual in one convenient location. These resources are designed to enhance your understanding of Arduino hardware and Arduino firmware, while making it easier to follow along with examples and practical applications from the book.

Whether you are using the manual as a day-to-day reference or as part of learning Arduino, this page brings together everything you need to extend your knowledge and apply concepts more effectively. From downloadable files and curated web links to Arduino sketches and visual references, each section supports hands-on learning and deeper exploration of Arduino Uno Rev 3 hardware.

Use the table of contents below to quickly access the materials that complement the book and get the most value from your Arduino hardware projects. As can be seen in the table of contents, there are five main sections on this page:

Table of Contents

Downloads for the Arduino Uno Hardware Manual

Access essential files and materials referenced throughout the Arduino Uno Hardware Manual. These downloads support your understanding of Arduino hardware and help you follow along with examples from the book.

PDF Drill Template File

The drill template file: drill-template.pdf as promised in sections 8.1 and 8.8 of the book. To save, right-click the link and choose Save Link As (or similar menu item, depending on browser) from the menu that pops up.

Important: Be sure to print the drill template file using a 1:1 scale, so that the template is not resized. After printing the template to a page, measure the 1cm or 1 inch markings to make sure that the page printed to scale.

Tip:The same drill templates can be found at the very back of the book after the index where they can be cut out and used as templates for drilling a base plate or for marking the mounting holes in an enclosure.

KiCad Template File

KiCad template file for Arduino Uno and Arduino Uno shield: arduino-uno-template.zip as promised in sections 1.1.6.5 and 8.8 of the book.

The KiCad template files were created using KiCad version 5.0.2 and need to be unzipped from the downloaded zip file before opening with KiCad. The template contains schematic and board files with the Arduino Uno R3 header sockets and drill holes placed in the correct positions on the board – ready for starting a new shield or Arduino board project.

Find all external resources referenced in the Arduino hardware manual in one convenient location. These links are curated to support further learning Arduino and deeper exploration of key topics.

Chapter 1 of the Arduino Uno Hardware Manual

1.1.3 Uses of the Arduino Uno

Wiring project wiring.org.co

Arduino Project Hub create.arduino.cc/projecthub

1.1.4.11 ICSP Header

Those readers interested in learning the C language to program Arduino boards may be interested in the book C Programming with Arduino ISBN 978-1-907920-46-2

1.1.5 Programming

The Arduino IDE is free to download from www.arduino.cc/en/software/

1.1.6.5 Custom PCB

KiCad (www.kicad.org) is an open-source EDA (Electronic Design Automation) software package that can be used to draw circuit diagrams and lay out PCBs.

1.1.7 Open-Source and Licensing

See creativecommons.org/licenses/ for more information on the various Creative Commons licenses.

For more details, see the page www.arduino.cc/en/Trademark on the Arduino website.

1.1.8 Third Party Compatible Boards

For more information on the various spin-off boards including official boards, clones, derivatives, compatibles and even counterfeits, see the article blog.arduino.cc/2013/07/10/send-in-the-clones/ on the Arduino blog.

1.1.9 Build Quality, Warranty and Safety

A full list of official Arduino boards can be found at www.arduino.cc/en/Main/Products on the Arduino website.

For more information on Arduino board compliance and for the warranty statement, see www.arduino.cc/en/Main/warranty

1.2.1 USB Bridge Firmware

The ATmega16U2 microcontroller and its firmware replaces the FT232RL USB to UART bridge chip from FTDI (ftdichip.com/) found on older Arduino boards (the Arduino Duemilanove www.arduino.cc/en/Main/arduinoBoardDuemilanove for example).

1.4 Arduino Uno History and Revisions

Readers who would like more information, see startingelectronics.org/articles/arduino/uno-r3-r2-differences/ for a full list of the differences between R1, R2 and R3 Arduino Uno boards.

1.6.1 Installing Software

Help documentation on installing the Arduino IDE software is available for Windows, MAC OS X and Linux. Follow the links below for your operating system.

1.6.1.1 Windows

www.arduino.cc/en/Guide/Windows/

1.6.1.2 MAC OS X

www.arduino.cc/en/Guide/macOS/

1.6.1.3 Linux

www.arduino.cc/en/Guide/Linux/

1.6.2 Getting Started, Examples and Reference

Getting started guides, examples and a software reference are all available on the Arduino website. Getting started guides and examples are a great way for new Arduino users to learn about building projects with Arduino and learning to write sketches.

1.6.2.1 Getting Started Guides

Links to getting started guides for any Arduino board can be found at:
www.arduino.cc/en/Guide/HomePage

Arduino Uno specific getting started guide:
www.arduino.cc/en/Guide/ArduinoUno/

1.6.2.2 Arduino Examples and Tutorials

An index to tutorials and examples at www.arduino.cc/en/Tutorial/HomePage/ on the Arduino website provides links to various categories.

1.6.2.3 Building Breadboard Circuits

A tutorial series at startingelectronics.org/beginners/start-electronics-now/ shows how to build breadboard circuits with some Arduino examples.

1.6.2.4 Arduino Software Reference

Arduino language and library reference: www.arduino.cc/reference/en/

1.6.3 Getting Help

Find the Arduino FAQ (Frequently Asked Questions) Update: FAQ now redirects to the support web page support.arduino.cc/hc/en-us

Problems and solutions can be found on the Arduino Troubleshooting page at
Updated link, troubleshooting now redirects to support page: support.arduino.cc/hc/en-us

The Arduino wiki at playground.arduino.cc/ is a user contributed collection of documentation and other useful information.

The Arduino Forum at forum.arduino.cc is a place where anyone can post a question that will be answered by community members. The forum can also be searched for other user’s questions which may already have answers. It is also a place where more experienced Arduino users can help others by answering questions.

1.6.4.1 Fritzing

Fritzing, found at fritzing.org on the web, provide a software package that can be used to draw Arduino breadboard circuits and then turn them into custom made printed circuit boards or PCBs.

1.6.4.2 Wiring

Find the Wiring project at wiring.org.co on the web.

1.6.4.3 Processing

Processing, found at processing.org on the web, is a programming language based on Java, and a software package for developing applications on a computer.

…

For more information, see www.arduino.cc/en/Tutorial/BuiltInExamples/PhysicalPixel/ on the Arduino website.

1.6.5 Arduino Uno Boards on the Web

Links to the web pages on the Arduino website for the Arduino Uno and Arduino Uno SMD boards follow.

1.6.5.1 Arduino Uno Web Page

Find the Arduino Uno web page at store.arduino.cc/products/arduino-uno-rev3/ which includes basic technical information and links to the circuit diagram and board build files in electronic format.

1.6.5.2 Arduino Uno SMD Web Page

Go to store.arduino.cc/products/arduino-uno-rev3-smd for the newest information on the Arduino Uno SMD, or to www.arduino.cc/en/Main/ArduinoBoardUnoSMD for the Arduino Uno SMD board page on the Arduino website. An electronic copy of the circuit diagram for the Arduino Uno SMD can be found here as well as the build files.

Chapter 2 of the Arduino Uno Hardware Manual

2.2 Atmel, Microchip and AVR

Microchip (www.microchip.com)

2.3.3.1 EEPROM Programming

Refer to the library reference www.arduino.cc/en/Reference/EEPROM for more information on using the EEPROM in sketches.

2.3.4.1 SD Cards (SPI Interface)

See www.arduino.cc/en/Reference/SD for more information on the Arduino SD card library.

2.3.4.3 SPI Devices

See the library reference www.arduino.cc/en/Reference/SPI for more information on the SPI library.

2.3.4.4 TWI and I²C Devices

See the library reference www.arduino.cc/en/Reference/Wire for more information on the Wire library.

2.7.5.1 Analog In Example Sketch

The corresponding tutorial page for the AnalogReadSerial example sketch can be found at www.arduino.cc/en/Tutorial/BuiltInExamples/AnalogReadSerial/ on the Arduino website, which shows how to connect a potentiometer to A0 to vary the voltage on this pin.

2.7.6 AREF Pin

For more information on the analogReference() function, see www.arduino.cc/reference/en/language/functions/analog-io/analogreference/

2.8.3 ATmega16u2 ICSP Header

More information on DFU programming can be found at www.arduino.cc/en/Hacking/DFUProgramming8U2 on the Arduino website and in section 5.1 of chapter 5 of this book.

2.8.4 ICSP Programming Resources

The following links provide more information on the AVRISP mkII, Atmel Studio and C programming of Arduino boards using Atmel Studio. Also see chapter 5.

AVRISP mkII – www.microchip.com/en-us/development-tool/atavrisp2

Atmel Studio – Update: Atmel Stduio has been replaced by Microchip Studio – www.microchip.com/en-us/development-tools-tools-and-software/microchip-studio-for-avr-and-sam-devices Old versions of Atmel Studio can be found at – www.microchip.com/en-us/development-tools-tools-and-software/avr-and-sam-downloads-archive

C Programming – wspublishing.net/avr-c/

2.8.5 Using an Arduino as an In-System Programmer

Find more information on the Arduino website at www.arduino.cc/en/Tutorial/BuiltInExamples/ArduinoISP/

Chapter 3 of the Arduino Uno Hardware Manual

3.2.2 ATmega328P Alternate Pin Functions

More information on each pin function can be found in the ATmega328 datasheet from the page www.microchip.com/en-us/product/ATmega328P on the Microchip website.

3.3.1.1 Pins as Outputs
Switching Heavier Loads with Transistors and Relays

For more details on interfacing Arduino boards and microcontrollers, refer to the appropriate texts or other sources such as the Interfacing With Hardware page playground.arduino.cc/Main/InterfacingWithHardware in the playground area on the Arduino website.

3.3.1.2 Pins as Inputs
Pull-down Resistor

Find the tutorial page at www.arduino.cc/en/Tutorial/BuiltInExamples/DigitalReadSerial/ on the Arduino website.

3.3.4.2 Accessing TWI Devices in Software

This means including the Wire.h header file in a sketch and using the Wire library object and functions found in the reference www.arduino.cc/en/Reference/Wire on the Arduino website.

3.3.5.2 Accessing SPI Devices in Software

Use the SPI object and functions from www.arduino.cc/en/Reference/SPI – the SPI reference page on the Arduino website.

3.3.5.3 Accessing SD Cards in Software

Go to www.arduino.cc/en/Reference/SD to find the SD card reference on the Arduino website.

3.3.6.1 Hardware Serial Port

Go to www.arduino.cc/reference/en/language/functions/communication/serial/ for the serial port library reference.

3.3.6.2 Software Serial Port

Go to www.arduino.cc/en/Reference/SoftwareSerial on the Arduino website for more information on the SoftwareSerial library.

3.7 Finding the Datasheets

3.7.1 ATmega328P Datasheet

Find the ATmega328P datasheet at www.microchip.com/en-us/product/ATmega328P on the Microchip website.

3.7.2 ATmega16U2 Datasheet

Go to www.microchip.com/en-us/product/ATmega16u2 to find the datasheet for the ATmega16u2 microcontroller used as the USB to serial bridge chip on Arduino Uno boards.

Chapter 4 of the Arduino Uno Hardware Manual

No links.

Chapter 5 of the Arduino Uno Hardware Manual

5.1 Updating the USB to Serial Bridge Firmware using DFU

For Windows computers, download the FLIP (Flexible In-system Programmer) software from Microchip at www.microchip.com/en-us/development-tool/FLIP

For additional information on Arduino DFU programming and for DFU programming using Linux and Mac, see www.arduino.cc/en/Hacking/DFUProgramming8U2 on the Arduino website.

5.2 Atmel Studio

USB ProgrammerPart NumberWeb Page
AVRISP mkIIatavrisp2www.microchip.com/en-us/development-tool/atavrisp2
AVR DragonATAVRDRAGONwww.microchip.com/en-us/development-tool/ATAVRDRAGON
Atmel-ICEatatmel-icewww.microchip.com/en-us/development-tool/atatmel-ice

To install Atmel Studio… Update: Atmel Studio has been replaced by Microchip Studio www.microchip.com/en-us/development-tools-tools-and-software/microchip-studio-for-avr-and-sam-devices on the Microchip website. For old versions of Atmel Studio, go to: www.microchip.com/en-us/development-tools-tools-and-software/avr-and-sam-downloads-archive

…

5.3.2 DFU Bootloader Firmware

At GitHub github.com/arduino/ArduinoCore-avr/tree/master/firmwares/atmegaxxu2/arduino-usbdfu is the link to the same source code.

5.3.3 USB to Serial Bridge Firmware

The same source code and HEX files can be found on GitHub at github.com/arduino/ArduinoCore-avr/tree/master/firmwares/atmegaxxu2/arduino-usbserial which contains the latest version of this code and HEX files.

5.4.2 Optiboot Bootloader Firmware

The same files can be found at github.com/arduino/ArduinoCore-avr/tree/master/bootloaders/optiboot on GitHub.

The Optiboot project on GitHub is at github.com/Optiboot/optiboot

Optiboot wiki can be found at github.com/Optiboot/optiboot/wiki

See github.com/Optiboot/optiboot/wiki/HowOptibootWorks for more details.

5.6 Alternative Firmware Programming Methods

Alternative methods for programming the bootloader to an Arduino Uno can be found at playground.arduino.cc/Main/ArduinoCoreHardware#Bootloader at the Arduino playground under the Bootloader section.

Using an Arduino as an ISP (In-system programmer) is also described on the Arduino website at www.arduino.cc/en/Tutorial/BuiltInExamples/ArduinoISP/

Refer to www.arduino.cc/en/Hacking/DFUProgramming8U2 for additional information on DFU programming the ATmega16u2.

Chapter 6 of the Arduino Uno Hardware Manual

6.4 Getting an Electronic Copy of the Circuit Diagram

Find the circuit diagram in PDF format, and the circuit diagram and PCB design file in Eagle format at store.arduino.cc/products/arduino-uno-rev3/ for the Arduino Uno. Look under the DOCUMENTATION tab for these files.

To view the files in Eagle format, the Eagle EDA software package will need to be downloaded from www.autodesk.com/products/eagle/free-download and installed.

Chapter 7 of the Arduino Uno Hardware Manual

7.4 Waveform Patterns and Measurement

PicoScope 2000 series digital PC oscilloscope, model number 2205A used for oscilloscope measurements.

Chapter 8 of the Arduino Uno Hardware Manual

8.7 Using Strip-board as a Shield

See startingelectronics.org/projects/arduino-projects/arduino-tiny-stripboard-shield/ for an example of fitting a piece of strip-board to an Arduino Uno using only three of the header sockets on the Arduino. An example project that uses the strip-board shield can be found at startingelectronics.org/projects/arduino-projects/arduino-tiny-temperature-shield/

8.8 Drill Template and KiCad Template

The drill template file as well as the KiCad template file can be found at the top of this page in the Downloads for the Arduino Uno Hardware Manual section.

The KiCad software package can be found at www.kicad.org where it can be downloaded free of charge and unrestricted.

Arduino Sketches from the Arduino Uno Hardware Manual

Arduino Sketches from the Arduino Uno Hardware Manual can be found below. Select the desired sketch and copy the code, then paste it to the Arduino IDE. Sketches are displayed below under the section number that they occur in in the book, with the page number that they can be found on.

1.5.2.2 – Page 45

Modified Blink sketch.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);     // configure L LED pin as output
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // switch L LED ON
  delay(200);                       // leave L LED ON for period
  digitalWrite(LED_BUILTIN, LOW);   // switch L LED OFF
  delay(200);                       // leave L LED OFF for period
}

2.7.4.1 – Page 71

Arduino Uno pin 12 configured as an output and driven high and low.

void setup() {
  pinMode(12, OUTPUT);    // configure digital pin 12 as an output pin
}

void loop() {
  digitalWrite(12, HIGH); // set pin 12 voltage to 5V on an Arduino Uno
  delay(500);
  digitalWrite(12, LOW);  // set pin 12 voltage to 0V or GND
  delay(500);
}


2.7.4.1 – Page 72

Defining a pin with a user friendly name.

#define MY_LED  12

void setup() {
  pinMode(MY_LED, OUTPUT);    // configure digital pin as an output pin
}

void loop() {
  digitalWrite(MY_LED, HIGH); // set pin voltage to 5V on an Arduino Uno
  delay(500);
  digitalWrite(MY_LED, LOW);  // set pin voltage to 0V or GND
  delay(500);
}

2.7.4.4 – Page 75

Arduino Uno PWM on pin 3 with 50% duty cycle.

void setup() {
  pinMode(3, OUTPUT);

  analogWrite(3, 127);
}

void loop() {
}

2.7.5.3 – Page 79

Calculating analog input voltage on Arduino Uno A0 pin.

void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(A0);                     // read ADC value
  float voltage = (5.0 / 1024.0) * (float)sensorValue;  // calculate voltage
  Serial.print(voltage);                                // display voltage
  Serial.println(" V");
  delay(1);
}

2.7.5.5 – Page 80

Arduino Uno analog pin A0 used as a digital output pin.

void setup() {
  pinMode(A0, OUTPUT);
}

void loop() {
  digitalWrite(A0, HIGH);
  delay(500);
  digitalWrite(A0, LOW);
  delay(500);
}

3.3.1.2 – Page 106

Pull-down Resistor

Read Arduino Uno pin 2 state with pull-down resistor.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(2, INPUT);
}

void loop() {
  if (digitalRead(2)) {
    // pin state is high or 1, switch is closed (pull-down resistor)
    digitalWrite(LED_BUILTIN, HIGH);  // switch L LED on
  }
  else {
    // pin state is low or 0, switch is open (pull-down resistor)
    digitalWrite(LED_BUILTIN, LOW);   // switch L LED off
  }
}

3.3.1.2 – Page 108

Pull-up Resistor

Read Arduino Uno pin 2 state with pull-up resistor.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(2, INPUT);
}

void loop() {
  if (digitalRead(2)) {
    // pin state is high or 1, switch is open (pull-up resistor)
    digitalWrite(LED_BUILTIN, LOW);    // switch L LED off
  }
  else {
    // pin state is low or 0, switch is closed (pull-up resistor)
    digitalWrite(LED_BUILTIN, HIGH);   // switch L LED on
  }
}

3.3.1.2 – Page 109

Internal Pull-up Resistors

Read Arduino Uno pin 2 state with internal pull-up resistor enabled.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(2, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(2)) {
    // pin state is high or 1, switch is open (pull-up resistor)
    digitalWrite(LED_BUILTIN, LOW);    // switch L LED off
  }
  else {
    // pin state is low or 0, switch is closed (pull-up resistor)
    digitalWrite(LED_BUILTIN, HIGH);   // switch L LED on
  }
}

3.3.4.2 – Page 113

Read the first byte from an AT24C16C EEPROM connected to the Arduino Uno TWI bus pins.

// Reads a single byte from a AT24C16C EEPROM on the TWI or I2C bus
#include <Wire.h>

void setup() {
  Wire.begin();         // join TWI bus as a master
  Serial.begin(9600);   // for displaying results in Serial Monitor window
  
  // *** Perform Random Read ***
  // address byte 0 of EEPROM
  Wire.beginTransmission((0xA0 >> 1));
  Wire.write(0x00);
  Wire.endTransmission();
  // read 1 byte from EEPROM at address 0
  Wire.requestFrom((0xA0 >> 1), 1);
  // *** End Perform Random Read ***

  while (Wire.available()) {          // check for response from EEPROM
    byte data8 = Wire.read();         // read byte from the EEPROM
    Serial.print("Byte read is: ");
    Serial.println(data8, HEX);       // display the byte
  }
}

void loop() {
}

7.4.2 – Page 172

Use all of the PWM pins on the Arduino Uno to produce PWM waveforms with different duty cycles.

void setup() {
  analogWrite(3, 51);     // PWM 20% 490Hz
  analogWrite(5, 89);     // PWM 35% 976Hz
  analogWrite(6, 127);    // PWM 50% 976Hz
  analogWrite(9, 166);    // PWM 65% 490Hz
  analogWrite(10, 204);   // PWM 80% 490Hz
  analogWrite(11, 230);   // PWM 90% 490Hz
}

void loop() {
}

7.4.3 – Page 172

Arduino Uno serial port or UART test square wave.

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.print('U');
}

7.4.5 – Page 175

Send a character on the Arduino Uno SPI bus.

#include <SPI.h>

void setup() {
  SPI.begin();
  SPI.beginTransaction(SPISettings(10000, MSBFIRST, SPI_MODE1));
}

void loop() {
  SPI.transfer('U');
  delay(1);
}

Extra Images and Screen Captures from the Arduino Uno Hardware Manual

View additional diagrams, images, and screen captures that complement the Arduino Uno Hardware Manual and provide enhanced visual reference for Arduino hardware concepts.

5.1 – Page 134 : FLIP Software

FLIP software for updating the USB to serial bridge firmware using the DFU method from section 5.1 Updating the USB to Serial Firmware using DFU.

Select the ATmega16U2 Device

Select the device to program in the FLIP software.

Flip device selection used in the Arduino Uno Hardware Manual

Open the USB Port

Open the USB port of the target device in the FLIP software. Click the Open button in the dialog box to continue.

Open the USB port in the FLIP software

Select the Correct Hex File

Load the HEX file for the ATmega16U2 in the FLIP application software.

FLIP software load HEX file

Program the ATmega16U2

Click the Run button to erase, program and verify the Flash memory of the ATmega16U2.

Click the Run button to erase, program and verify

Programming Completed

The FLIP software application as it appears after successfully programming the target device.

FLIP software after programming

5.3.1 – Page 137 to Page 138 : ATmega16U2 ICSP Connection

The procedure for connecting the ISP plug of a USB programmer into the ICSP header for the ATmega16U2 on an Arduino Uno follows. This is described in section 5.3.1 Backing up the ATmega16U2 Firmware with Atmel Studio of the Arduino Uno Hardware Manual.

Key on ISP Connector Blocks Connection

As can be seen in the image below, the key on the ISP connector of the programmer prevents it from being plugged into the ICSP header for the ATmega16U2 on an Arduino Uno.

ISP key blocking connection to ICSP header of Arduino Uno as referenced in the Arduino Uno Hardware Manual

Wires Used for Connection

Six wires that have a single pin male connector on one end and single pin female connector on the other end can be used to connect the ISP plug to the Arduino Uno ATmega16U2 ICSP header. The wires can be seen in the image below.

Wire connectors used to connect the ISP plug to the ICSP header for the ATmega16U2 of an Arduino Uno

Plug the Wires into the ISP Plug

Plug the wires, three at a time, into the ISP Plug as the image below shows.

Plugging wires into the ISP plug

Plug the Wires into the ICSP Header

Now plug the extension wires from the ISP plug to the ICSP header.

The next image shows the extension wires connecting from the ISP plug of the USB programmer to the ICSP header for the ATmega16U2 on an Arduino Uno.

Wires plugged into the ATmega16U2 ICSP header from the USB programmer

A close-up of the connection can be seen in the following image.

Close up of wires plugged into the ATmega16U2 ICSP header

Arduino Uno Hardware Manual Errata

Report errata for the Arduino Uno Hardware Manual, First Edition on our Contact Us page. Be sure to clearly state the book name and edition when reporting errata. In addition, give the page number and section number and name. Clearly state and explain the errata that you are reporting.

Errata submitted are included below.

Page 79 – Incorrect Calculation

2.7.5.3 Calculating Analog In Voltage

The second sentence in the first paragraph of section 2.7.5.3, at the top of page 79, reads as follows:

On the Arduino Uno we know that the default reference voltage is 5V, so the calculation becomes 1024 ÷ 5 × <analog value read on pin> = voltage.

The part shown in bold above is incorrect, it should be 5 ÷ 1024 which is how it is shown in the sketch that follows – the sketch that follows is correct. The sentence should therefore read as follows:

On the Arduino Uno we know that the default reference voltage is 5V, so the calculation becomes 5 ÷ 1024 × <analog value read on pin> = voltage.