Software programs, called sketches, are created on a computer using the Arduino integrated development environment (IDE). The IDE enables you to write and edit code and convert this code into instructions that Arduino hardware understands. The IDE also transfers those instructions to the Arduino board (a process called uploading).

The Arduino board is where the code you write is executed. The board can only control and respond to electricity, so specific components are attached to it to enable it to interact with the real world. These components can be sensors, which convert some aspect of the physical world to electricity so that the board can sense it, or actuators, which get electricity from the board and convert it into something that changes the world. Examples of sensors include switches, accelerometers, and ultrasound distance sensors. Actuators are things like lights and LEDs, speakers, motors, and displays.

There are a variety of official boards that you can run your Arduino sketches on and a wide range of Arduino-compatible boards produced by members of the community.

The most popular boards contain a USB connector that is used to provide power and connectivity for uploading your software onto the board. Figure 5-1 shows the board used for the robots in this book, the Arduino Leonardo.

Figure 5-1. Basic board: the Arduino Leonardo

You can get boards that are smaller and boards with more connections. The Leonardo is used with these robotics projects because it is inexpensive but you can use other boards such as the Uno if you prefer.

Add-on boards that plug into Arduino to extend hardware resources are called shields. The robots covered in this book use a shield that controls the direction and speed of the motors, see Figure 5-2:

Figure 5-2. Motor Shield plugged into the Arduino Leonardo

Online guides for getting started with Arduino are available at http://arduino.cc/en/Guide/Windows for Windows, http://arduino.cc/en/Guide/MacOSX for Mac OS X, and http://www.arduino.cc/playground/Learning/Linux for Linux.

The Arduino software for Windows, Mac, and Linux can be downloaded from http://arduino.cc/en/Main/Software.

Installing Arduino on Windows

The Windows download is a ZIP file. Unzip the file to any convenient directory—Program Files/Arduino is a sensible place.

Unzipping the file will create a folder named Arduino-1.0.<nn> (where <nn> is the version number of the Arduino release you downloaded). The directory contains the executable file (named Arduino.exe), along with various other files and folders. Double-click the Arduino.exe file and the splash screen should appear (see Figure 5-3), followed by the main program window (see Figure 5-4). Be patient, as it can take some time for the software to load.

Figure 5-3. Arduino splash screen (Version 1.0 in Windows 7)

Installing Arduino on OS X

The Arduino download for the Mac is a disk image (.dmg); double-click the file when the download is complete. The image will mount (it will appear like a memory stick on the desktop). Inside the disk image is the Arduino application. Copy this to somewhere convenient—the Applications folder is a sensible place. Double-click the application once you have copied it over (it is not a good idea to run it from the disk image). The splash screen will appear, followed by the main program window (Figure 5-4).

Figure 5-4. IDE main window (Arduino 1.0 on a Mac)

Plug the board into a USB port on your computer and check that the green LED power indicator on the board illuminates. The location of the LED is indicated in Figure 5-5.

Figure 5-5. The Leonardo

If you have a factory fresh board, an orange LED (labeled “Pin 13 LED” in Figure 5-5) should flash on and off when the board is powered up (boards come from the factory preloaded with software to flash the LED as a simple check that the board is working).

Use the Arduino IDE to create, open, and modify sketches that define what the board will do. You can use buttons along the top of the IDE to perform these actions (shown in Figure 5-6), or you can use the menus or keyboard shortcuts (some are shown in Figure 5-7).

Figure 5-6. Arduino IDE

The Sketch Editor area is where you view and edit code for a sketch. It supports common text editing keys such as Ctrl-F (⌘-F on a Mac) for find, Ctrl-Z (⌘-Z on a Mac) for undo, Ctrl-C (⌘-C on a Mac) to copy highlighted text, and Ctrl-V (⌘-V on a Mac) to paste highlighted text.

Figure 5-7 shows how to load the Blink sketch (the sketch that comes preloaded on a new Arduino board).

After you’ve started the IDE, go to the File→Examples menu and select 1.Basics→Blink, as shown in Figure 5-7. The code for blinking the built-in LED will be displayed in the Sketch Editor window.

Figure 5-7. IDE menu (selecting the Blink example sketch)

Before the code can be sent to the board, it needs to be converted into instructions that can be read and executed by the Arduino controller chip; this is called compiling. To do this, click the compile button (the top-left button with a tick inside), or select Sketch→Verify/Compile (Ctrl-R, ⌘-R on a Mac).

You should see a message that reads “Compiling sketch...” and a progress bar in the message area below the text editing window. After a second or two, a message that reads “Done Compiling” will appear. The black console area will contain the following additional message:

Binary sketch size: 1026 bytes (of a 32256
byte maximum)

The exact message may differ depending on your board and Arduino version; it is telling you the size of the sketch and the maximum size that your board can accept.

The final message telling you the size of the sketch indicates how much program space is needed to store the controller instructions on the board. If the size of the compiled sketch is greater than the available memory on the board, the following error message is displayed:

Sketch too big; 
see http://www.arduino.cc/en/Guide/Troubleshooting#size for tips 
on reducing it.

If this happens, you need to make your sketch smaller to be able to put it on the board, or get a board with higher capacity. You will not have this problem with the Blink example sketch.

If there are errors in the code, the compiler will print one or more error messages in the console window. These messages can help identify the error.

As you develop and modify a sketch, you should also consider using the File→Save As menu option and using a different name or version number regularly so that as you implement each bit, you can go back to an older version if you need to.

To transfer your compiled sketch to the Arduino board, connect your board to your computer using the USB cable. Load the sketch into the IDE as described in Using the IDE.

Next, select Tools→Board from the drop-down menu and select the name of the board you have connected.

Now select Tools→Serial Port. You will get a drop-down list of available serial ports on your computer. Each machine will have a different combination of serial ports, depending on what other devices you have used with your computer.

On Windows, they will be listed as numbered COM entries. If there is only one entry, select it. If there are multiple entries, your board will probably be the last entry.

On the Mac, your board will be listed twice (you can use either one):

/dev/tty.usbmodemXXXXXXX
/dev/cu.usbmodemXXXXXXX

If you have an older board, it will be listed as follows:

/dev/tty.usbserial-XXXXXXX
/dev/cu.usbserial-XXXXXXX

Each board will have different values for XXXXXXX. Select either entry.

Click on the upload button (in Figure 5-6, it’s the second button from the left), or choose File→Upload to I/O board (Ctrl-U, ⌘-U on a Mac).

The software will compile the code, as in Using the IDE. After the software is compiled, it is uploaded to the board. If you look at your board, you will see the LED stop flashing, and two lights (labeled as Serial LEDs in Figure 5-5) just below the previously flashing LED should flicker for a couple of seconds as the code uploads. The original light should then start flashing again as the code runs.

The IDE will display an error message if the upload is not successful. Problems are usually due to the wrong board or serial port being selected or the board not being plugged in. The currently selected board and serial port are displayed in the status bar at the bottom of the Arduino window

If you have trouble identifying the correct port on Windows, try unplugging the board and then selecting Tools→Serial Port to see which COM port is no longer on the display list. Another approach is to select the ports, one by one, until you see the lights on the board flicker to indicate that the code is uploading.

Tabs provide a convenient way to organize code when your sketch starts to grow. It enables you to keep functionally related code together and simplifies sharing this code across more than one sketch.

The arrow in the upper right of Figure 5-8 points to the button which invokes a drop-down window of tab related functions. This window displays the names of the tabs and offers a list of commands:

Figure 5-8. IDE tabs

Each tab is a separate file and when you copy these files to other sketches you add the tab to that sketch.

Because there are many functional modules used in this book and these are shared across most of the sketches, tabs are used extensively. Figure 5-8 shows the myRobot sketch, discussed in the next chapter, that uses tabs for infrared sensor code (irSensors) and for program constants and definitions (robotDefines.h).

The download code for this book (see How to Contact Us) contains three libraries that are required to run all the sketches described in the book. These libraries are in a folder called libraries in the zip. You need to copy these so they are in a folder called libraries inside your Arduino document folder. To find the Arduino document folder, open Preferences (Arduino→Preferences on Mac; File→Preferences on Windows) and note the sketchbook location. Navigate to that directory in a file system browser (such as Windows Explorer or the OS X Finder) or at the terminal. If no libraries folder exists, create one and put the folder you unzipped inside it.

If the Arduino IDE is still running, quit and restart it. The IDE scans this folder to find libraries only when it is launched. If you now go to the menu Sketch→Import Library, at the bottom, below the gray line and the word Contributed, you should see the library you have added.

If the libraries provide example sketches, you can view these from the IDE menu; click File→Examples, and the library's examples will be under the library's name in a section between the general examples and the Arduino distributed libraries example listing.

If the library examples do not appear in the Examples menu or you get a message saying “Library not found” when you try to use the library, check that the libraries folder is in the correct place with the name spelled correctly. A library folder named <LibraryName> (where <LibraryName> is the name for the library) must contain a file named <LibraryName>.h with the same spelling and capitalization. Check that additional files needed by the library are in the folder.