Chapter 1 ■ IntroduCtIon
2
Chapter 3 presents “The Matrix” construction project. It uses an LED matrix to produce a display that
can provide instant display of CPU utilization for each of its cores. It also displays bar graphs for memory and
disk I/O utilization. If you don’t want to construct this project, you can install the htop utility instead.
Chapters 4 and 9 cover an exciting tool that is also included in the book’s software, the PiSpy logic
analyzer tool. This provides a simple-to-use logic analyzer for your Pi, requiring no additional hardware. It
allows you to inspect and capture GPIO signal events, whether the GPIO is an input or output. Through the
use of the direct memory access (DMA) peripheral, PiSpy can capture signal changes up to about 1–2 MHz.
The GtkWave command is then optionally invoked automatically to display the captured data.
Chapter 5 is dedicated to the GPIO gp command. All utilities provided with this book use proper
command line option processing as used by the standard Unix commands. The chapter begins with a brief
discussion of what Unix command line conventions are and then works through the gp command use cases
with explanations.
Chapter 6 introduces the piclk utility, which can display or alter the configuration of the general
purpose clock (or PWM clock). Experiments with the clock are included.
Chapter 7 expands on the clock concept by examining the Pulse Width Modulation (PWM) peripheral.
The pipwm utility and its options are explored in combination with PiSpy. PiSpy illustrates the effect of
different configuration settings.
Chapter 8 takes a light look at what GPIO is and the Complementary MOS (CMOS) technology that it is
made from. Electronics students will find the examination helpful in explaining what CMOS is and avoiding
some pitfalls in interfacing. Additionally CMOS inputs are examined with a brief discussion of chip static
protection schemes.
Chapter 9 provides a detailed look at the PiSpy logic analyzer and describes the various features of
its application.
Chapter 10 looks at GPIO input processing, focusing particularly on the problem of debouncing input
signals from buttons and switches.
Chapter 11 is a software-focused chapter. It provides a fast track to using C++ and the STL in a very easy
and pragmatic way. The STL provides the programmer great benefits in programming time and reliability. In
this chapter we look at the most popular containers and example code fragments are provided throughout.
Chapter 12 is the multithreaded software designed to take advantage of all four CPU cores within an
efficient web server. The server is based on the libevent library behind the scenes, but C++ classes are used
to provide a very simple interface. This allows you to build and customize your own web server with very
little mainline code. The provided piweb project can be used and extended.
Appendixes A through C document the librpi2 C++ classes for programming GPIO. With the provided
library, it is a simple matter to directly control GPIO from your own code. The appendixes provide you with
easy-to-follow documentation and examples for the various class methods supported.
Appendixes D and E describe some other C++ classes that might be useful for people wanting to work
with Matrix or 7-segment displays. Appendix F describes classes that have to do with gathering system
performance metrics as used by the mtop utility.
Appendix G provides some additional information about some of the remaining advanced classes
found in librpi2.
Software for This Book
You will want to download the open source software written for this book. It is available from two sources:
• www.apress.com/9781484217382
• https://github.com/ve3wwg/raspberry_pi2.git
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