C H A P T E R  1

Arduino Basics

by Enrique Ramos

This first chapter is dedicated to Arduino, one of the two cornerstones of this book. The following pages cover the basics of the Arduino hardware and software. By the end of the chapter, you will have installed the platform on your computer and you will have programmed two examples using the Arduino integrated development environment (IDE).

The structure of an Arduino sketch will be analyzed and each function explained. You will learn about the Arduino input and output pins. You will also learn the basic concepts of electricity, circuits, and prototyping techniques that you will be using throughout the book.

It is highly likely that this is not the first book on Arduino that you have held in your hands. If you are an experienced Arduino user, you should consider reading these pages as a refresher. If you are a complete beginner, read carefully!

Figure 1-1. Arduino Uno

What is Arduino?

Arduino is an open source electronics prototyping platform composed of a microcontroller, a programming language, and an IDE. Arduino is a tool for making interactive applications, designed to simplify this task for beginners but still flexible enough for experts to develop complex projects.

Since its inception in 2005, more than 200,000 Arduino boards (see Figure 1-1) have been sold, and there is a rapidly increasing number of projects using Arduino as their computing core. The Arduino community is vast, and so is the number of tutorials, reference books, and libraries available. Being open source means that there are Arduino clones that you can choose for your projects. Advanced Arduino users are constantly developing shields for the available Arduinos as well as completely new Arduino-compatible boards specializing in different tasks.

The intentional simplicity of approach to the Arduino platform has permitted an access to physical computing for people who would have never thought of using or programming a microcontroller before the Arduino/Wiring era.

A Brief History of Arduino

Arduino was born in 2005 at the Interaction Design Institute Ivrea, Italy, as a fork of the open source Wiring Platform. The founders of the project, Massimo Banzi and David Cuartielles, named the project after Arduin of Ivrea, the main historical character of the town.

Hernando Barragán, a student at the same Institute, along with Diego Gonzalez Joven, had developed Wiring in 2003 as his master's thesis, which was supervised by Massimo Banzi and Casey Reas (one of the initiators of Processing). The idea behind Wiring was to allow an easy introduction to programming and sketching with electronics for artists and designers—in a similar mindset in which Casey Reas and Ben Fry had developed Processing some years earlier (you will learn more on the history of Processing in Chapter 3).

Arduino was built around Wiring but developed independently from 2005. The two projects are still very much alive, so everything you will be doing in this book with Arduino could also be done with Wiring boards and IDE.

Installing Arduino

The first thing you need to do if you want to work with Arduino is to buy an Arduino board and a standard USB cable (A-to-B plug if you are using an Arduino Uno). Well, of course you will need more than this if you want to build any reasonable useful application, but for the moment you'll just work with the bare essentials.

Arduino runs on Windows, Mac OS X, and Linux, so there’s a version of Arduino for you whatever your OS. Go to the Arduino software web site at http://arduino.cc/en/Main/Software and download the version of the software compatible with your system. If after reading the following sections you are still having trouble with the installation, you can have more detailed information at http://arduino.cc/en/Guide/HomePage.

Installation on Mac OS X

After you have downloaded the .zip file, uncompress it. You can drag the Arduino application to your Applications folder, and then run from there. Pretty easy, right?

If you are using a board older than Arduino Uno (Duemilanove, Diecimila, or older), you need to install the drivers for the FTDI chip on the board. You can find the drivers and the instructions at http://www.arduino.cc/en/Guide/MacOSX.

Installation on Windows

First, download the Windows .zip file and uncompress it. You will see a folder called arduino-1.0. This is your Arduino folder and you need to store it somewhere in the computer from where you can later run the program. The Program Files folder would seem like a reasonable place for the Arduino software, but feel free to choose an alternative location.

You need to install the Arduino drivers before you can start working with your board. Assuming you are installing an Arduino Uno, follow these steps:

• Plug your board to your computer, and wait for Windows to start the driver installation process. After a while, it will fail. No problem.
• Click Start menu and open the Control Panel.
• Go to System and Security, then System and then Device Manager.
• Find the Arduino Uno port listed under Ports (COM & LPT).
• Right-click on it, and choose “Update Driver Software,” selecting “Browse my Computer for Driver Software.”
• Finally, navigate and select the Arduino Uno’s driver file named ArduinoUNO.inf located in the Drivers folder of the Arduino software folder you have just downloaded. Windows will successfully install the board now.

Installation on Linux

If you are working on Linux, the installation process is slightly different depending on your Linux distribution, and unfortunately we don’t have the space to detail all of them in this book. You can find all the information you need at http://www.arduino.cc/playground/Learning/Linux.

Testing the Arduino

Once you have installed the Arduino software and drivers, you need to perform a little test to make sure that everything is working properly.

Arduino has a built-in LED connected to pin 13, so you can actually test the board without having to connect any extra hardware to it. Among the numerous Arduino examples included with the Arduino IDE, there is an example called Blink that makes this built-in LED to blink every second. You will learn more about pins, LEDs, and Arduino code in the following sections, but for the moment, you are going to use this example as a way to find out if your Arduino is communicating properly with your computer and if the sketches can be uploaded to the board.

Connect your Arduino board to your computer and run the Arduino software. On the Tools menu, select Board, and make sure that the right kind of board is selected. In our case, we want to check that the Arduino Uno board is ticked (see Figure 1-2).

Figure 1-2. Board selection

After this, select the serial device under the Serial Port option in your Tools menu. If you are working on Mac OS X, the port should be something with /dev/tty.usbmodem (for the Uno or Mega 2560) or /dev/tty.usbserial (for older boards) in it (see Figure 1-3). If you are using Windows, the port is likely to be COM 3 or higher.

Figure 1-3. Serial port

Now everything should be ready for you to upload your first program to your Arduino board. You will be using one of the classic Arduino examples for this test. Click the Open button on your toolbar and navigate to 1. Basics Blink, as shown in Figure 1-4. Then upload the sketch by clicking the Upload button (the one with the arrow pointing right on your toolbar). After some seconds, you will get a message saying “Done Uploading” on the status bar, and the LED marked with a capital “L” on your board will start blinking every second. If you succeeded in this, your Arduino is correctly set up, and you can move on to learning about the Arduino hardware and software.

Figure 1-4. Opening the Blink example

Arduino Hardware

You can think of the Arduino board as a little brain that allows you to connect together a vast range of sensors and actuators. The Arduino board is built around an 8-bit Atmel AVR microcontroller. Depending on the board, you will find different chips including ATmega8, ATmega168, ATmega328, ATmega1280, and ATmega2560. The Arduino board exposes most of the microcontroller’s input and output pins so they can be used as inputs and outputs for other circuits built around the Arduino.

If you go to http://arduino.cc/en/Main/Hardware, you will find a surprisingly vast range of Arduino boards. Each one of them has been designed with a different purpose in mind and thus has different amount of pins and electronics on board (see Figure 1-5).

The Arduino Uno is, at the time of writing, the simplest Arduino board to use. For the rest of the book, whenever we refer to Arduino board, we actually mean an Arduino Uno unless explicitly stated (we will also work with Arduino Nano and Arduino Lilypad in further chapters).

Figure 1-5. Official Arduino boards (from http://arduino.cc)

Arduino is open source hardware and as such, every official board’s schematics are available to the public as EAGLE files (EAGLE is a PCB layout, autorouter, and CAM software by Cadsoft). In this way, if none of the board designs seem to satisfy your needs, or if you want to have access to cheaper boards, you can actually make your own Arduino-compatible board. If you want to know how to do this, get Arduino Robotics (Apress, 2011) and you will learn all you need to know to make your own Arduino clone. If you are thinking of creating your own Arduino clones for commercial purposes, make sure you read the Arduino policy at http://arduino.cc/en/Main/Policy.

Arduino Input and Output Pins

The Arduino Uno has 14 digital input/output pins and six analog input pins, as shown in Figure 1-6. As mentioned, these pins correspond to the input/output pins on your ATmega microcontroller. The architecture of the Arduino board exposes these pins so they can be easily connected to external circuits.

Arduino pins can be set up in two modes: input and output. The ATmega pins are set to input by default, so you don’t need to explicitly set any pins as inputs in Arduino, although you will often do this in your code for clarity.

Figure 1-6. Arduino digital pins (top) and analog pins (bottom)

Digital Pins

Arduino has 14 digital pins, numbered from 0 to 13. The digital pins can be configured as INPUT or OUTPUT, using the pinMode() function. On both modes, the digital pins can only send or receive digital signals, which consist of two different states: ON (HIGH, or 5V) and OFF (LOW, or 0V).

Pins set as OUTPUT can provide current to external devices or circuits on demand. Pins set as INPUT are ready to read currents from the devices connected to them. In further chapters, you will learn how to set these pins to INPUT so you can read the state of a switch, electric pulses, and other digital signals. You will also learn how to work with digital pins set as OUTPUT to turn LED lights on and off, drive motors, control systems, and other devices.

Six of these pins can also be used as pulse width modulation pins (PWM). Chapter 4 covers what this means and how to use PWM pins.

Analog Input Pins

The Atmega microcontrollers used in the Arduino boards contain a six-channel analog-to-digital converter (ADC). The function of this device is to convert an analog input voltage (also known as potential) into a digital number proportional to the magnitude of the input voltage in relation to the reference voltage (5V).

The ATmega converter on your Arduino board has 10-bit resolution, which means it will return integers from 0 to 1023 proportionally based on the potential you apply compared to the reference 5V. An input potential of 0V will produce a 0, an input potential of 5V will return 1023, and an input potential of 2.5V will return 512.

These pins can actually be set as input or output pins exactly as your digital pins, by calling them A0, A1, etc. If you need more than six digital input or output pins for a project, you can use your analog pins, reading or writing to them as if they were digital pins. You will be using this trick in Chapter 10 when you need 16 digital input pins.

Pull-Up Resistors

Whenever you are reading a digital input from one of your Arduino pins, you are actually checking the incoming voltage to that pin. Arduino is ready to return a 0 if no voltage is detected and a 1 if the voltage is close to the supply voltage (5V). You need to ensure that the incoming voltages are as close as possible to 0 or 5V if you want to get consistent readings in your circuit.

However, when the pins are set to input, they are said to be in a high-impedance state, which means it takes very little current to move the pin from one state to another. This can be used to make applications that take advantage of this phenomenon, such capacitive touch sensors or reading LEDs as photodiodes, but for general use this means that the state of a disconnected input pin will oscillate randomly between 1 and 0 due to electrical noise.

To avoid this, you need to somehow bias the input to a known state if no input is present. This is the role of the ATmega built-in pull-up resistors.

Figure 1-7. Pull-up and pull-down resistors (from Wikipedia)

Looking at Figure 1-7, you can see that whenever the switch is open, the voltage Vout, which is the voltage you will read at the input pin, is very near Vin, or 5V. When the switch is closed, all the current flows through the resistor to ground, making Vout very close to ground, or 0V. In this way, your input pin is always driven to a consistent state very close to 0 or 5V.

The pull-down resistor works the same way, but the signal will be biased or pulled down to ground when the switch is open and to 5V when the switch is closed.

The ATmega chip has 20K pull-up resistors built in to it. These resistors can be accessed from software in the following manner:

Arduino Shields

Arduino shields are boards that have been designed to perform a specific task and can be plugged on top of a compatible Arduino board directly, extending the Arduino pins to the top so they are still accessible.

There are a few official Arduino shields and a vast number of unofficial ones that you can find on the Internet (see Figures 1-8 and 1-9). And the best thing, you can create your own Arduino shields by using an Arduino-compatible Protoshield or by printing your own PCB compatible with the Arduino design.

Figure 1-8. Arduino XBee Shield (left) and Arduino Prototyping Shield (right)

Figure 1-9. Official Arduino shields

Arduino IDE

The Arduino IDE is a cross-platform application written in Java and derived from the IDE for Processing and Wiring. An IDE is basically a program designed to facilitate software development. The Arduino IDE includes a source code editor (a text editor with some useful features for programming, such as syntax highlighting and automatic indentation) and a compiler that turns the code you have written into machine-readable instructions.

But all you really need to know about the Arduino IDE is that it is the piece of software that will allow you to easily write your own Arduino sketches and upload them to the board with a single click. Figure 1-10 shows what the IDE looks like.

Figure 1-10. Arduino IDE

Take a moment to familiarize yourself with the IDE. Table 1-1 offers a description of all the buttons you will find in the toolbar.

Note that the line of text that you see at the bottom-right of the IDE is actually telling you the Arduino board and the serial port you have selected. If they don’t correspond to what you expect, you can change them following the steps from the section “Testing the Arduino.”

If these symbols look somewhat different from those in your Arduino IDE, you probably have an old version of the Arduino tools. Go to http://arduino.cc/en/Main/Software and download the latest version. At the time of writing, Arduino 1.0 is the current software version.

Serial Monitor

The Serial Monitor (at the top right of your Arduino IDE) is a tool to display the serial data being sent from the Arduino board to the computer (see Figure 1-11). You need to match the baud rate on your serial monitor to the baud rate you specify in the Arduino sketch sending data. The baud rate is the number of symbol changes transmitted per second.

The serial monitor is very useful in the debugging of Arduino programs (the process of finding and fixing the defects in the program so it behaves as expected). Whenever you’re not sure what is wrong with the code, ask Arduino to print messages to the serial monitor so you can peek into the state of the program at that precise moment.

Figure 1-11. Arduino Serial Monitor

You will make extensive use of serial communication throughout the book, as it is the main way to get Arduino to communicate with Processing and thus with the Kinect data.

Arduino Language

The Arduino language is implemented in C/C++ and based in Wiring. When you write an Arduino sketch, you are implicitly making use of the Wiring library, which is included with the Arduino IDE. This allows you to make runnable programs by using only two functions: setup() and loop(). As mentioned, the Wiring language is inspired by Processing, and the Arduino language structure is inherited from the Processing language, where the equivalent functions are called setup() and draw(), as you will see in Chapter 3.

You need to include both functions in every Arduino program, even if you don’t need one of them. Let’s analyze the structure of a simple Arduino sketch using again the Blink example. Open your Arduino IDE, and select Open   1.Basics Blink.

The setup() Function

The setup() function is run only once, right after you upload a new sketch to the board, and then each time you power up your Arduino. You use this function to initialize variables, pin modes, start libraries, etc. In this example, the setup() function is used to define pin 13 as output:

The loop() Function

The loop() function is run continuously in an endless loop while the Arduino board is powered. This function is the core of most programs.

In this example, you turn pin 13’s built-in LED on using the function digitalWrite() to send a HIGH (5V) signal to the pin. Then you pause the execution of the program for one second with the function delay(). During this time, the LED will remain on. After this pause, you turn the LED off, again using the function digitalWrite() but sending a LOW (0V) signal instead, and then pause the program for another second. This code will loop continuously, making the LED blink.

This code would not actually be seen as a valid C++ program by a C++ compiler, so when you click Compile or Run, Arduino adds a header at the top of the program and a simple main() function so the code can be read by the compiler.

Variables

In the previous example, you didn’t declare any variables because the sketch was rather simple. In more complex programs, you will declare, initialize, and use variables.

Variables are symbolic names given to a certain quantity of information. This means you will associate a certain piece of information with a symbolic name or identifier by which you will refer to it.

Variable Declaration and Initialization

In order to use a variable, you first need to declare it, specifying at that moment the variable’s data type. The data type specifies the kind of data that can be stored in the variable and has an influence in the amount of memory that is reserved for that variable.

As Arduino language is based on C and C++, the data types you can use in Arduino are the same allowed in C++. Table 1-2 lists some of the data types you will use throughout this book. For a complete listing of C++ data types, you can refer to C++ reference books and Internet sites.

When you declare the variable, you need to write the type specifier of the desired data type followed by a valid variable identifier and a semicolon. In  the following lines, you declare an integer, a character, and a Boolean variable:

This code has declared the variables, but their value is undetermined. In some cases, you want to declare the variable and set it to a default value at the same time. This is called initializing the variables. If you want to do this, you can do it in the following way:

By doing this, your three variables are set to specific values and you can start using them from this moment on.

In other cases, you want to declare the variables first and initialize them later. You will see this happening frequently, as it’s necessary when you want to declare the variable as global but its value depends on other variables or processes happening within the setup(), draw(), or other functions.

Variable Scope

When you declare your variables, the place you do it within the code will have an impact on the scope in which the variable will be visible. If you declare your variable outside of any function, it will be considered a global variable and will be accessible from anywhere in the code. If you declare your variable within a function, the variable will be a local variable and will only be accessible from within the same function. Let’s do an example from the Blink sketch.

This code will upload and run smoothly, behaving exactly as the original Blink example. You have declared and initialized the integer ledPin at the beginning of your program, outside of any function, so it is considered a global variable visible from within the other functions in the code.

The variable myOtherPin, on the other hand, has been defined within the setup() function. You have used the variable to set the pin defined by the variable to OUTPUT. If you tried to use the variable from the loop() function, Arduino would throw an error at you, saying “’myOtherPin’ was not declared in this scope”. And that’s right; you have declared and initialized the variable within the setup() function, making it a local variable and only visible from within the function in which it was declared.

Your First Arduino Project

You are going to write an example Arduino sketch involving all the elements you just learned in the previous sections. This is only a very first step in the development of an Arduino project, but it will be enough to summarize this chapter on Arduino basics.

You are going to build a very simple circuit first, and then you will program it using your Arduino IDE. You will need your Arduino board, a breadboard, an LED, a 220-ohm resistor, a potentiometer, and some wires to build this example.

Breadboard

When working with electronics, it is often useful to “sketch” the circuit quickly so you can test it before building it in a more permanent form. Using a solderless breadboard, you can easily prototype electronics by plugging elements together. As the elements are not soldered to the board, the board can actually be reused as many times as you want (see Figures 1-12 and 1-13).

Figure 1-12. Bredboard connection diagram

Figure 1-13. Project sketched on a breadboard

Note that the pins flanked by blue and red lines on your breadboard (the top two rows and the bottom two rows in Figure 1-13) are connected together horizontally, so you can use them to provide 5V and ground to all the elements on the project. The other pins are connected in vertical strips broken in the middle. You use these linked strips to connect the resistor to the LED and the potentiometer pins to 5V, ground, and the Arduino Analog Input Pin 0.

Building the Circuit

Try to replicate this circuit on your breadboard and connect it to the Arduino as you see happening in Figure 1-14. The LED is connected to analog pin 11, and the middle pin of the potentiometer is connected to analog pin 0. The ground and 5V cables are connected to the Arduino GND and 5V pins. Note that the LED has a shorter leg (cathode), which needs to be connected to ground. The longer one is connected to the resistor. If you are curious about the functioning of LEDs and why you are using a 220-ohm resistor, there is a whole section on resistors in Chapter 7.

The goal of this project is to control the brightness of the LED by turning the potentiometer. A potentiometer is basically a variable resistor that you control by turning the knob. Note that the potentiometer is not connected to the LED or the resistor at all; it’s just connected to the Arduino board. You acquire the values coming from the potentiometer from Arduino and use these values to drive the brightness of the LED. All of this is done in the Arduino code.

Programming the Arduino

Now you are going to write the code that will permit you to drive the LED by turning your potentiometer. You will use serial communication to check the values that you are getting from the potentiometer in runtime using the Serial Monitor.

First, you declare a global integer variable called ledPin that defines the LED pin number during the execution of the program.

The setup() Function

After this, you write the setup() function in which you start serial communication at a baud rate of 9600 and define the pinMode of your LED pin to OUTPUT so you can write to it.

Figure 1-14. Your first Arduino project

The loop() Function

In the loop() function, the first thing you do is declare a new local integer variable called sensorValue to store the value of the potentiometer connected to analog pin 0. You initialize the variable to this value by using the analogRead() function and specifying A0 (Analog 0) as your pin. If you were to read analog pin 1, you would write A1, and so on.

Then you print the value from the potentiometer to the serial buffer using the function Serial.println(). If you open the Serial Monitor while the program is running, you will see that the values coming from the potentiometer range from 0 to 1023.

You want to use this value to set the brightness of your LED, but you have stated that the scope of the brightness needs to be in a range of 0 to 255. The solution to this issue will be mapping the values of the potentiometer from its range to the range of the potentiometer. You will use this technique very often in your projects; luckily, Arduino has a function to perform this operation called map().

The map() function takes five arguments: map(value, fromLow, fromHigh, toLow, toHigh).

The argument value is the current value to be mapped. fromLow and fromHigh define the lower and higher values of the source range, and toLow and toHigh, the lower and higher values of the target range.

In your case, your LED brightness needs to be defined as map(sensorValue,0,1023,0,255), so if the sensor value is 1023, the LED brightness is 255. The map() function will always return an integer, even in the case that the mapping would result in a floating point number.

Once you have determined the brightness of the LED, you write this value to the LED pin using the function analogWrite(pin, value).

Upload this program to your Arduino board, and you will be able to change the brightness of your LED by turning the potentiometer. You will develop more advanced control techniques in Chapter 4, but before you move on, let’s go through some basic concepts on electronics.

Circuit Diagrams

We just described the circuit using photos and text. But when we get to more complicated circuits, this will not be enough. The way circuits should be represented is with circuit diagrams, or schematics.

Circuit diagrams show the components of a circuit as simplified standard symbols and the connections between the devices. Note that the arrangement of the elements on a diagram doesn’t necessarily correspond to the physical arrangement of the components.

There are numerous software packages that facilitate the drawing of schematics, but there is one designed to be used by non-engineers, and it works nicely with Arduino projects: Fritzing.

Fritzing

Fritzing is an open source tool developed at the University of Applied Sciences of Potsdam in Germany; it’s aimed at artists and designers who want to develop their prototypes into real projects. You can (and should) download Fritzing from http://fritzing.org.

Fritzing has a graphical interface that allows the user to build the circuit as in the physical world, connecting together breadboards, Arduinos, LEDs, resistors, etc. Then you turn this visual representation into a circuit diagram just by changing the view, as shown in Figures 1-15 and 1-16.

Figure 1-15. Breadboard view of your project in Fritzing

Figure 1-16. Schematics view of your project in Fritzing

Electronic Symbols

Electronic symbols, or circuit symbols, are the pictograms used to represent electrical components and devices in the schematics. There are several international standards for these graphical symbols. In this book, we will use ANSI in all the circuit diagrams and symbols. Table 1-3 is a list of some electronics symbols that you will see used in this book and some of the IEC equivalents for reference.

Electricity

Throughout the rest of the book, you will be building circuits, using motors, and talking a lot about electronics in general. One of the advantages of Arduino is that it makes for an easy introduction to electronics for beginners, but if you are completely new to electronics, here are some basic concepts.

AC/DC

Mains electricity is alternating current (AC), but you will be using direct current (DC) for all your projects. AC is actually cheaper to produce and transmit from the power plants to your home. That is the reason why all the plugs in our households give us alternating current. But AC is also more difficult to control, so most electronic devices work with a power supply that converts AC into DC.

The current provided by your USB is DC, as is the current you get from a battery or a computer power supply, so you won’t work with AC at all in this book. Every time we speak about electricity or current in the book, we are referring to DC.

Ohms Law

Electricity, or electrical current is, very generally, the movement of electrons through a conductor. The intensity (I) of this current is measured in amperes (A).

The force pushing the electrons to flow is called voltage, which is the measure of the potential energy difference relative between the two ends of the circuit. Voltage is measured in Volts, or V.

The conductor through which the electrons are flowing will oppose some resistance to their passage. This force is called resistance, and it is measured in ohms (Ω).

Georg Ohm published a treatise in 1827 describing measurements of voltage and current flowing through circuits. Today, one of these equations has become known as Ohm’s law, and it ties together voltage, current, and resistance.

Putting this into words, the equation states that the current flowing through a conductor (I) is directly proportional to the potential difference (V) across the two ends. The constant of proportionality is called resistance  (R).

Resistance is then the measure of the opposition to the passage of an electric current through an element. The opposite of resistance is conductance (G).

Ohm’s law can be rewritten in three different ways depending on which elements of the equation you already know and which one you are trying to calculate.

Joule’s Law

Joule’s first law, also known as Joule Effect, was declared by James Prescott Joule in the 1840s. This law states that the power dissipated in a resistor, in terms of the current through it and its resistance, is

P = I² · R

If you apply the previous equations to Joule’s law, you will be finally able to calculate the power in watts as a value derived by multiplying current by voltage.

P = I · V

This helps you to choose the correct power rating for elements such as resistors and to calculate the power consumption from battery-driven supplies. This, in turns, lets you estimate how long your project will run on a set of batteries.

Summary

This first chapter has taken you through an overview of the Arduino platform in which both the Arduino hardware and software have been thoroughly analyzed.

Your Arduino board should be properly configured now, the Arduino IDE should be installed on your computer, and you should be communicating seamlessly with your board via USB. You have had a brief refresher course on basic electrical concepts, and you have warmed up with a couple of examples.

This introduction doesn’t intend to be a substitute for more introductory works. If this is your first contact with Arduino, you might want to consider having a look at some other titles like Beginning Arduino (Apress, 2010) before you go deeper into this book, or at least have one at hand just in case.

After finishing this chapter, hopefully you are craving more exciting projects, but don’t rush into it! You still have to go through some fundamental concepts about the other cornerstone of this book: the Kinect.