Arduino was built to access the outside world. Much of that access is through the GPIO pins. Each Arduino board has a different set of GPIO pins, so in this section, I'll provide details on the GPIO pins available on the most common variant of Arduino: Arduino Uno. Then, I'll also document the additional capability of the Arduino Mega. Finally, I'll show the GPIO capability of a more limited Arduino: Arduino FLORA.

First, let's focus on the Arduino Uno. As described in Chapter 1, Powering on Arduino, the Arduino Uno comes with a set of 14 digital and six analog I/O pins, along with some additional pins to provide power and serial I/O.

Fortunately, the pins are actually well labeled on the board itself, as shown in the following image:

The following table shows a list of pins that are available and a brief description of what each pin can do, starting at the upper-right side of the board and going clockwise. A more in-depth description of these pins will come...