Operation Manual

Many of these hobby shops sprang up in the wake of the Arduino, an open-source project to create an educational-friendly
microcontroller prototyping platform. With the Raspberry Pi appealing to much the same audience as the Arduino—albeit for
very different tasks—the majority are investigating support for the Pi in addition to their existing product lines.
Buying from a hobby specialist has several advantages. If the products are sold as working with the Pi, then they’ve been tested
for that specific reason—taking much of the guesswork out of the equation. Several companies also design their own add-on
hardware for various platforms, with the Pi being no exception. These devices, designed to address a need in the community,
may include additional ports and/or extra hardware, or can otherwise extend the functionality of the target device.
In the UK, one of the most popular hobby specialists is oomlout. Founded by open-source enthusiasts working with Arduino
hardware, it’s an excellent source of add-on kits as well as common components including push-buttons, displays and
transistors. Unlike the larger retailers, oomlout equips its components with all necessary extras—such as pull-up resistors for the
push-buttons—and a circuit schematic for easy assembly. Where possible, sample source code is also provided to get you up
and running as quickly as possible.
In the US, Adafruit offers a similar service. Founded with the intention of making open-source add-ons for the Arduino boards,
Adafruit offers a wide selection of components and kits—including one of the first add-on boards designed specifically for the
Raspberry Pi (see Chapter 13, “Add-on Boards”, for more details).
The websites for both retailers can be found here:
oomlout: http://www.oomlout.co.uk
Adafruit: http://www.adafruit.com
The GPIO Port
The Raspberry Pi’s GPIO port is located on the top-left of the printed circuit board, labelled P1. It’s a 26-pin port, fitted with
two rows of 13 male 2.54 mm headers at the factory. The spacing of these headers is particularly important: 2.54 mm pin
spacing (0.1 inches in imperial measurements) is a very common sight in electronics, and is the standard spacing for prototyping
platforms that include stripboards and breadboards.
Each pin of the GPIO port has its own purpose, with several pins working together to form particular circuits. The layout of the
GPIO port can be seen in Figure 12-2.
Figure 12-2: The Raspberry Pi’s GPIO port and its pin definitions
Pin numbers for the GPIO port are split into two rows, with the bottom row taking the odd numbers and the top row the even
numbers. It’s important to keep this in mind when working with the Pi’s GPIO port: most other devices use a different system for