Programming Arduino Getting Started with Sketches

Figure 1-2
ATmega328 block diagram
Other Components
Above the microcontroller is a small, silver, rectangular component. This is a quartz
crystal oscillator. It ticks 16 million times a second, and on each of those ticks, the
microcontroller can perform one operation—addition, subtraction, or another
mathematical operation.
To the right of the crystal is the Reset switch. Clicking on this switch sends a logic
pulse to the Reset pin of the microcontroller, causing the microcontroller to start its
program afresh and clear its memory. Note that any program stored on the device will be
retained, because this is kept in non-volatile flash memory—that is, memory that
remembers even when the device is not powered.
To the right of the Reset button is the Serial Programming Connector. It offers another
means of programming the Arduino without using the USB port. Because we do have a
USB connection and software that makes it convenient to use, we will not avail ourselves
of this feature.
In the top-left corner of the board next to the USB socket is the USB interface chip.
This chip converts the signal levels used by the USB standard to levels that can be used
directly by the Arduino board.
The Origins of Arduino
Arduino was originally developed as an aid for teaching students. It was subsequently (in
2005) developed commercially by Massimo Banzi and David Cuartielles. It has since gone
on to become enormously successful with makers, students, and artists for its ease of use
and durability.
Another key factor in its success is that all the designs for Arduino are freely available

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under a Creative Commons license. This has allowed many lower-cost alternatives to the
boards to appear. Only the name Arduino is protected, so such clones often have
“*dunino” names, such as Boarduino, Seeeduino, and Freeduino. However, the official
boards manufactured in Italy still sell extremely well. Many big retailers sell only the
official boards, which are nicely packaged and of high quality.
Yet another reason for the success of Arduino is that it is not limited to microcontroller
boards. There are a huge number of Arduino-compatible shield boards that plug directly
into the top of an Arduino board. Because shields are available for almost every
conceivable application, you often can avoid using a soldering iron and instead plug
together shields that can be stacked one upon another. The following are just a few of the
most popular shields:
• Ethernet, which gives an Arduino web-serving capabilities
• Motor, which drives electric motors
• USB Host, which allows control of USB devices
• Relays, which switches relays from your Arduino
Figure 1-3
shows an Arduino Uno with an Ethernet shield attached.