Learning to Hack Hardware - Raspberry Pi User Guide - page 194

IN EARLIER CHAPTERS, you learned how the Raspberry Pi can be turned into a flexible plat-
form for running a variety of software. In this, it's not alone: any desktop or laptop can run the
same software, and in many cases run it far faster than the Pi's low-power processor can manage.
The Pi has another trick up its sleeve, though, which places it above and beyond the capabili-
ties of the average PC: its 26-pin general-purpose input-output (GPIO) port, located on the top-
left of the Pi's printed circuit board.
The GPIO enables the Pi to communicate with other components and circuits, and allows it
to act as a controller in a larger electronic circuit. Through the GPIO port, it's possible to have
the Pi sense temperatures, move servos and talk to other computing devices using a variety
of different protocols including Serial Peripheral Interface (SPI) and Inter-Integrated Circuit
(I²C) . Chapter 14, “The GPIO Port”, provides details on working with the GPIO pins.
Before you can get begin building circuits to use with the Pi's GPIO port, however, you're
going to need some additional equipment and to understand some of the language sur-
rounding the world of electronics.
Electronic Equipment
To start building circuits that can be controlled by the Pi's GPIO port, you'll need various
components and tools. The following list provides a sample shopping list for getting started
with electronics:
❍ Breadboard —An electronic breadboard provides a grid of holes spaced at 2.54 mm
intervals into which components can be inserted and removed. Below each grid is a
series of electrical contacts, which allow components in the same row to be connected
together without wires. A breadboard is a valuable tool for electronics work, because it
allows you to quickly make mock-up circuits that can be modified without needing to
be soldered or desoldered.
❍ Wires —While a breadboard allows some components to be joined without wiring,
you'll still need wires to connect one row to another. These are known as jumper wires ,
and if you're working on a breadboard, it's a good idea to get solid-core wire rather
than stranded-core wire. Solid-core wire is easier to insert into the breadboard's holes
compared to stranded. It's also helpful to get various colours, so you can colour-code
each connection according to its purpose.
❍ Resistors —he vast majority of electrical circuits make use of components called
resistors , and the example projects in this chapter are no exception. Resistors are mea-
sured in ohms , written as the symbol Ω. Always try to have a handful each of a variety
of common values: 2.2 KΩ, 10 KΩ, and 68Ω are good values to start with. Some retail-
ers carry resistor kits, which include a wide range of useful values.