Raspberry Pi Mechatronics Projects HOTSHOT 1849696225 %7BE56CA9D0%7D %5BYamanoor %26 Yamanoor 2015 01 26%5D {E56CA9D0} [Yamanoor & 26]

User Manual: 1849696225 %7BE56CA9D0%7D Raspberry Pi Mechatronics Projects Hotshot %5BYamanoor %26 Yamanoor 2015-01-26%5D

Open the PDF directly: View PDF .
Page Count: 606

Download
Open PDF In Browser	View PDF

Raspberry Pi Mechatronics Projects
HOTSHOT

Table of Contents
Raspberry Pi Mechatronics Projects HOTSHOT
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Support files, eBooks, discount offers, and more
Why subscribe?
Free access for Packt account holders
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Mission briefing
Why is it awesome?
Your Hotshot objectives
Mission checklist
Task 1
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Classified intel
Reader feedback
Customer support
Downloading the example code
Downloading the color images of this book
Errata
Piracy
Questions

1. Hello World
A quick introduction to the Raspberry Pi
Features of a Raspberry Pi
Where can I buy a Raspberry Pi?
Requirements to get started with the Raspberry Pi
Operating systems on the Raspberry Pi
Getting started with Raspbian
Downloading Raspbian
Flashing image on to the SD card
Windows
Linux
A command-line interface-based approach
Identifying the SD card mount point
Unmount the SD card
Flash the SD card
GUI-based approach
Setting up the Raspberry Pi
Mission briefing
Why is it awesome?
Your Hotshot objectives
Mission checklist
Hunting and gathering
Engage thrusters
Objective complete – mini debriefing
Setting up the GPIO
Engage thrusters
Installing GPIO libraries
Objective complete – mini debriefing
GPIO programming using Python
Engage thrusters
An alternative to quick2wire – RPi.GPIO

Objective complete – mini debriefing
Electrical output of our program
Engage thrusters
Objective complete – mini debriefing
Introduction to the Pi Crust – a prototyping platform for the Raspberry Pi
Mission accomplished
Hotshot challenge
2. A Raspberry WebIDE Example
Mission briefing
Why is it awesome?
Your Hotshot objectives
Mission checklist
Installation, features, and usage of the Occidentalis operating system from Adafruit
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Setup of a remote login into the Raspberry Pi
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Installation of the Raspberry Pi WebIDE
Engage thrusters
Objective complete – mini debriefing
Python development on the WebIDE
Prepare for lift off
Quick introduction to the I2C interface
Configuring the I2C interface on the Raspberry Pi
Engage thrusters
Objective complete – mini debriefing
Test and debugging examples using the WebIDE
Prepare for lift off

Engage thrusters
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
3. The Arduino Raspberry Pi Interface
Mission briefing
Why is it awesome?
Where can you buy an Arduino?
Your Hotshot objectives
Mission checklist
Installing the Arduino IDE
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Programming the Arduino using the Raspberry Pi
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Raspberry Pi AlaMode
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
The Weasley weather clock
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Controlling the stepper using the Arduino
Prepare for lift off
Engage thrusters
Counterclockwise rotation of the stepper motor
Objective complete – mini debriefing

Controlling the RGB LED Strip using the Arduino
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
I2C Communication using the Arduino (optional)
Prepare for lift off
Engage thrusters
The 7-Segment display
8x8 LED matrix
BlinkM
Proximity sensor
Objective complete – mini debriefing
Serial port communication with the Raspberry Pi
Engage thrusters
Python program for the Weasley clock
Arduino acknowledgement to control signal
Control flow for the weather clock
Temperature data
Control of the RGB LED strip
Control of stepper via serial port
Programming the weather forecast position
8x8 matrix control
BlinkM control
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
4. Christmas Light Sequencer
Mission briefing
Why is it awesome?
Your objectives
Mission checklist

Interface the devices to the Raspberry Pi
Prepare for lift off
Engage thrusters
Connecting multiple appliances to the Raspberry Pi
Objective complete – mini debriefing
Setting up the digitally addressable RGB matrix
Prepare for lift off
Where can I buy them?
Engage thrusters
How does it work?
Lighting up the RGB LED strip
An Arduino-based control
Objective complete – mini debriefing
Interface of an audio device
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Installing the web server
Prepare for lift off
Engage thrusters
Objective complete – mission debriefing
Interfacing the web server
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Mission accomplished
References
5. Internet of Things Example – An E-mail Alert Water Fountain
Mission briefing
Why is it awesome?
Your objectives

Mission checklist
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Installation of the Flask framework
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Controlling RGB LEDs from a web page
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Setup of the e-mail alerts in the fountain
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
6. Raspberry Pi as a Personal Assistant
Mission briefing
Why is it awesome?
Your objectives
Mission checklist
Setting up the e-mail feed parser
Prepare for lift off
Engage thrusters
Setting up the parser for reminders and events
Prepare for lift off
Engage thrusters
Designing an enclosure design for the personal assistant
Prepare for lift off

Engage thrusters
Setting up the assembly for the dish monitor
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Setting up sensors for the key alert system
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Mission accomplished
Hotshot challenges
References
7. Raspberry Pi-based Line Following Robot
Mission briefing
Why is it awesome?
Your Hotshot objectives
Mission checklist
Assembly of the Pi Plate for the line following robot
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Sensor selection, interface, and data interpretation
Engage thrusters
Light Dependent Resistors
Infrared emitter/detector
Machine-vision-based line following robot
Sensor selection
Objective complete – mission debriefing
Implementation of line following logic based on sensor data
Prepare for lift off
Engage thrusters

Objective complete – mini debriefing
Testing the motor driver circuit
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Preparation of the line following course
Prepare for lift off
Engage thrusters
Use electrical tape and build a track
Designing the chassis for the line following robot
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
A step-by-step assembly of the robot
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
References
8. Connect Four Desktop Game using Raspberry Pi
Mission briefing
Why is it awesome?
Your objectives
Mission checklist
Hello world example with the pygame
Prepare for lift off
Engage thrusters
Playing sounds using the pygame module
Building menus using the pygame module
Objective complete – mini debriefing

Getting started with the Connect Four game (UI and sound effects)
Prepare for lift off
Engage Thrusters
Adding a menu for the game
Adding sounds to the game
Objective complete – mission debriefing
Interfacing game inputs using the PiFace module
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
A brief description of the Connect Four Game AI
Prepare for lift off
Engage thrusters
Main game loop
Objective complete – mini debriefing
Marquee design and control (optional)
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Setup of the switches using a cardboard box
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
References
9. The Raspberry Pi-enabled Pet/Wildlife Monitor
Mission briefing
Why is it awesome?
Your objectives
Mission checklist

Installing and testing the python-twisted framework
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Setting up and testing Spark Core to interact with appliances
Prepare for lift off
Engage Thrusters
Objective complete – mini debriefing
Installing and testing the Google Coder project on the Raspberry Pi
Prepare for lift off
Engage thrusters
Objective complete – objective complete
A brief overview of a bird feeder that triggers a camera
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Alternatives and project ideas to consider
Mission accomplished
Hotshot challenge
10. Raspberry Pi Personal Health Monitor
Mission briefing
Why is it awesome?
Your Hotshot objectives
Mission checklist
Setting up a web server to record health parameters
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
A simple exercise tool using the Raspberry Pi
Prepare for lift off
Engage thrusters

A mini project idea
Objective complete – mini debriefing
Setting up an e-mail feed parser to refill a prescription as well as remind the user about
an upcoming doctor’s appointment
Engage thrusters
Setting up a reminder for doctor’s appointments
Objective complete – mini debriefing
A simple tool that reminds a person to take his/her pills
Prepare for lift off
Engage thrusters
Other project ideas
Objective complete – mini debriefing
Mission accomplished
Hotshot challenge
11. Home Automation using Raspberry Pi
Mission briefing
Why is it awesome?
Your objectives
Mission checklist
A simple example that controls limited indoor and outdoor lighting in the evening
Prepare for lift off
Software prerequisites
Engage thrusters
Objective complete – mini debriefing
Alternative solutions and some project ideas to consider
A customary web server example
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Turning on a lawn sprinkler only when there is no rain forecast!
Prepare for lift off
Engage thrusters

Objective complete – mini debriefing
Gaining remote access to your Raspberry Pi to control appliances
Some project ideas to consider
Mission accomplished
12. Using a Raspberry Pi for Science and Education
Mission briefing
Why is it awesome?
Your Hotshot objectives
Improving your vocabulary using the Raspberry Pi
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Raspberry Pi and Khan Academy
Some ideas to consider
Building a science fair exhibit using the Raspberry Pi
Prepare for lift off
Engage thrusters
Objective complete – mini debriefing
Some simple educational experiments using the Raspberry Pi
Hotshot challenge
13. Tips and Tricks
Mission briefing
Why is it awesome?
Your objectives
Mission checklist
Setting up Raspberry Pi as a development platform
#1 – Simple trick for Python development via remote login
#2 Web development using Google Coder
#3 Adafruit Occidentalis
#4 Java Development using the Raspberry Pi
#5 The Thingbox project

Remotely logging in the Raspberry Pi from anywhere on the Internet
Problems that might be encountered while using Raspberry Pi
SD card corruption
Power issues
Devices powered by USB
Cool add-on hardware sources developed for the Raspberry Pi platform
The Raspberry Pi model B versus B+, model A versus A+
Project ideas that can be implemented over a weekend
Useful resources for the Raspberry Pi
Raspberry Pi Foundation’s forums:
Raspberry Pi Stack Exchange:
Element 14’s Raspberry Pi community:
Mission accomplished
Index

Raspberry Pi Mechatronics Projects
HOTSHOT

Raspberry Pi Mechatronics Projects
HOTSHOT
Copyright © 2015 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means, without the prior written permission of the
publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the
information presented. However, the information contained in this book is sold without
warranty, either express or implied. Neither the authors, nor Packt Publishing, and its
dealers and distributors will be held liable for any damages caused or alleged to be caused
directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the
companies and products mentioned in this book by the appropriate use of capitals.
However, Packt Publishing cannot guarantee the accuracy of this information.
First published: February 2015
Production reference: 1190215
Published by Packt Publishing Ltd.
Livery Place
35 Livery Street
Birmingham B3 2PB, UK.
ISBN 978-1-84969-622-7
www.packtpub.com

Credits
Authors
Sai Yamanoor
Srihari Yamanoor
Reviewers
Guy Scheffer
Sreedhar Vaddi
Cheuk Yu
Commissioning Editor
Usha Iyer
Acquisition Editors
Usha Iyer
Rebecca Pedley
Sam Wood
Content Development Editor
Susmita Sabot
Technical Editor
Parag Topre
Copy Editor
Janbal Dharmaraj
Project Coordinator
Milton D’souza
Proofreaders
Simran Bhogal
Maria Gould
Ameesha Green
Paul Hindle
Indexer
Hemangini Bari
Graphics
Sheetal Aute

Disha Haria
Production Coordinators
Aparna Bhagat
Manu Joseph
Cover Work
Aparna Bhagat

About the Authors
Sai Yamanoor is a mechatronics engineer working for a private start-up school in the San
Francisco Bay Area where he builds devices that help students achieve their full potential.
He completed his degree in mechanical engineering at Carnegie Mellon University,
Pittsburgh, PA, and his undergraduate work in mechatronics at Sri Krishna College of
Engineering and Technology, Coimbatore, India. His interests, deeply rooted in DIY and
open software and hardware cultures, include developing gadgets and apps that improve
quality of life, Internet of Things, crowdfunding, education, and new technologies. In his
spare time, he plays with various devices and architectures such as Raspberry Pi, Arduino,
Galileo, Android devices, and others. Sai shares his adventures with mechatronics at the
aptly named “Mechatronics Craze” blog at http://mechatronicscraze.wordpress.com/.
I want to thank my parents for encouraging me in all my endeavors and for making me
what I am today. I am grateful to my brother who has helped shape my career all these
years. I look forward to working with Srihari on similar projects in the future. I sincerely
thank Mr. S. Balaji Raghavendra who has been a great source of inspiration to me while
pursuing my undergraduate degree. I am also thankful to Susmita Sabot and the entire
support team at Packt Publishing who were patient and understood the circumstances
during difficult times.
Srihari Yamanoor is a nature photographer and mechanical engineer with experience
working in medical device design and CAD/CAM. He completed his master’s in science
as well as a degree in engineering from Stanford University. His work and interests in
medical devices include women’s health, cancer, orthopedics, and cardiovascular diseases,
as well as newer areas such as digital health and electronic health records. He has several
thousands of hours of CAD experience behind him and is also certified among other
things as a SolidWorks expert, simulation professional, and a SolidWorks instructor. His
interests range from engineering and education to social entrepreneurship, animal welfare,
and crowdfunding.
I would like to thank my parents, Narasimhan and Yasoda Venakatakrishnan, for their
steadfast support in my education and efforts throughout the years, culminating in projects
such as this book. Over the course of the years, many friends have helped both Sai and me
grow in many ways. For this reason, I would like to say a big word of thanks, in no
particular order, to Rika Catherine Hirachi, Anna Liu Jao, Shirupa Gupta, Patrick Nguyen,
Vishnu Prasad Ramachandran, Andrew Eib, Christopher Ma, and Karthik Palaniappan. I
am sure I am missing some names, and for this, I apologize in advance. I would also like
to thank my gracious mentors, Dr. Kevin Waldron, Dr. James Stubbs, Russell Sampson,
Mukund Patel, and as I fondly call him, Cyril “Master”, all of whom have given me advice
and shown me the way. I would like to especially thank my first cat, Squeaky, and the
felines Bob, Saxon, and Fishbone, that have followed me, for inspiring me and pushing
me to stay on track and keep an eye on the big picture.

About the Reviewers
Sreedhar Vaddi has 4 years of experience in big data, 4 years in cloud computing, and 15
years in Java. His experience includes work in the fields of big data security,
biomedical/healthcare, mobile security, financial services (wholesale, mortgage,
investment, and brokerage), the Web (marketplace, crowdsourcing, and advertising), news
and entertainment, property and casualty insurance, software product development, and
scientific research.
He has hands-on experience as an architect working on enterprise mobile applications,
Hadoop, SaaS, PaaS, IaaS, the cloud, rich enterprise applications, n-tier enterprise
systems, Enterprise Application Integration (EAI) in web-enabling legacy systems, IBM
Mainframe and SAP, and SOA web services with Java2 and JEE.
He has also worked in all phases of SDLC, namely designing, developing, performance
testing, and implementing Web-2.0, Web-UI, server-side, middleware, and mobile
applications. He has also worked with Big 5 Consulting and Fortune 100 companies. He
has led teams of sizes varying from 2 to 80 across the globe in different time zones,
cultures, and dialects.
He is an administrator of JEE containers (Geronimo, WebSphere, Weblogic, JBoss, and
Tomcat) and CDH. He is also a technical consultant at a stealth mode start-up in animal
care in the clinical trials industry. He is a diligent worker and quick learner with excellent
problem solving, presentation, and mentoring skills.
Cheuk Yu is pursuing a bachelor’s degree in electrical engineering at the University of
California, Los Angeles (UCLA), with an emphasis on circuit and signal processing. He
worked on multiple embedded systems projects using various microcontrollers such as
Arduino, Teensy, and Raspberry Pi. As a student researcher for the ELFIN CubeSat
Mission at UCLA, he also has hands-on experience working on printed circuit boards,
including designing and testing avionics and ground support equipment boards. Besides
work and study, he is also an amateur radio operator and astronomer.

www.PacktPub.com

Support files, eBooks, discount offers, and
more
For support files and downloads related to your book, please visit www.PacktPub.com.
Did you know that Packt offers eBook versions of every book published, with PDF and
ePub files available? You can upgrade to the eBook version at www.PacktPub.com and as
a print book customer, you are entitled to a discount on the eBook copy. Get in touch with
us at  for more details.
At www.PacktPub.com, you can also read a collection of free technical articles, sign up
for a range of free newsletters and receive exclusive discounts and offers on Packt books
and eBooks.

https://www2.packtpub.com/books/subscription/packtlib
Do you need instant solutions to your IT questions? PacktLib is Packt’s online digital
book library. Here, you can search, access, and read Packt’s entire library of books.

Why subscribe?
Fully searchable across every book published by Packt
Copy and paste, print, and bookmark content
On demand and accessible via a web browser

Free access for Packt account holders
If you have an account with Packt at www.PacktPub.com, you can use this to access
PacktLib today and view 9 entirely free books. Simply use your login credentials for
immediate access.

Preface
The Raspberry Pi is a quaint example of technological innovations that come by once
every two or three decades and set off a revolution that touches every aspect of human life
from scientific exploration to entertainment to education. What is exciting this time
around is that there are several such innovations happening simultaneously. They might
sound like, and are in a way, buzzwords, but they are in fact real, and are changing our
lives in so many ways, so few of which we are consciously aware of. We are speaking of
innovations in entrepreneurship, such as crowdsourcing or the emergence of DIY with an
almost cult-like following to innovations in technology that are current, such as 3D
printing and Internet of Everything, and innovations that are impending such as 4D
printing, smart manufacturing, and much more.
The Raspberry Pi has already found several uses as evidenced by hundreds of websites,
project examples, and crowdsourcing campaigns. People have used the Pi to build robots,
teach programming, restore old gaming consoles, stream videos, collect data, and do many
other things. The Pi itself has gone through design iterations and continues to spur
competing systems. People have taken advantage of this and have hooked up the Pi to
many different ecosystems, expanding its ubiquity and utility.
The purpose of this book is to help those who are excited about the Raspberry Pi and have
project ideas in mind, or would simply like to get their hands dirty and practice
implementing projects so that they can then use that knowledge for other endeavors. We
tried to take a practical approach, introducing the Pi in the first couple of project that you
can skip if you are familiar with the Raspberry Pi and have used it before. We then discuss
projects of increasing complexity. We have also attempted to diversify the projects to
demonstrate various uses for the Pi throughout the book.

What this book covers
Project 1, Hello World, will introduce the Raspberry Pi and remind you of things that you
should know as you proceed through the book. We will set up the Raspberry Pi and blink
an LED.
Project 2, A Raspberry WebIDE Example, will take you through Python development
using a browser. We will use the Adafruit WebIDE and lead you through the development
process using Adafruit products as props for the examples.
Project 3, The Arduino Raspberry Pi Interface, is inspired by the Harry Potter series, and
in an effort to show our love for this series, we have created a clock similar to the
innovative and endearing Weasley clock using the Raspberry Pi and an Arduino. This
project, of course, allows the clock to report back weather conditions.
Project 4, Christmas Light Sequencer, discusses holidays as the best time for DIY projects,
and if you are ever starved of ideas, holidays are the best time to cook up ideas. We picked
a Christmas-themed project to demonstrate controlling appliances connected to a local
network using Raspberry Pi.
Project 5, Internet of Things Example – An E-mail Alert Water Fountain, follows the
theme of the previous project. We will show you how to control a decorative fountain such
that anytime you receive a new e-mail, your fountain’s light will flash an alert (this can
also be switched to receive Twitter alerts).
Project 6, Raspberry Pi as a Personal Assistant, will show you how you can use the Pi as
your personal assistant, reminding you of chores, setting alarms, and doing everything at
your command.
Project 7, Raspberry Pi-based Line Following Robot, will take you through the simplest of
all robots, the line following bot, with Raspberry Pi at the helm. This project will show
you the way for this and other complex robotics projects you wish to implement.
Project 8, Connect Four Desktop Game using Raspberry Pi, follows the instant-classic
theme for the Raspberry Pi, which includes games. All manners of gaming applications,
including the revival of archaic games to new ones and mods, are being created using the
Raspberry Pi. We will implement the game using a push button interface.
Project 9, The Raspberry Pi-enabled Pet/Wildlife Monitor, will walk you through a fun
example of a bird feeder monitor that allows you to trigger a photo capture each time the
bird approaches the feeder. You can think of extending this to other pets, or say, the feral
cats in your colony.
Project 10, Raspberry Pi Personal Health Monitor, is a project where we set up a simple
web server to record our personal health parameters, build a simple tool to remind
ourselves to remain physically active, and remind ourselves to refill a prescription via email alerts.
Project 11, Home Automation using Raspberry Pi, is a project where we will show you
how to control appliances using a twisted network where the appliance is connected to a

platform such as an Arduino. The Raspberry Pi acts as a server that controls all such nodes
in the network.
Project 12, Using a Raspberry Pi for Science and Education, is a project packed with
examples, including a vocabulary learning tool, a web host for Khan Academy, and a
windmill generator science exhibit. Have fun learning and teaching!
Project 13, Tips and Tricks, is a project packed with tips and tricks that will help you use
the Raspberry Pi!
You can also get the videos, tips and tricks, and many more things related to the projects at
http://diywithpi.com/.

What you need for this book
To get started, you will need the Raspberry Pi, a monitor, a keyboard, a power source, and
preferably, a laptop or personal computer running on any OS—Windows, Linux, or Apple.
Other hardware and software recommendations are made in the individual projects, and
you are welcome to replace them with what you see fit. A working knowledge of Python is
preferred, but not required.

Who this book is for
This book is primarily aimed at hobbyists and do-it-yourself enthusiasts as well as those
looking to implement specific projects using low cost hardware and software centered
around the Raspberry Pi. Basic exposure to electronics, programming, and Internet usage
is assumed. We have tried to take a pragmatic approach, implementing the projects and
showing how you can do this on your own.

Conventions
In this book, you will find several headings appearing frequently. To give clear
instructions of how to complete a procedure or task, we use:

Mission briefing
This section explains what you will build, with a screenshot of the completed project.

Why is it awesome?
This section explains why the project is cool, unique, exciting, and interesting. It describes
what advantage the project will give you.

Your Hotshot objectives
This section explains the eight major tasks required to complete your project.
Task 1
Task 2
Task 3
Task 4
Task 5
Task 6
Task 7
Task 8

Mission checklist
This section explains any pre-requisites for the project, such as resources or libraries that
need to be downloaded, and so on.

Task 1
This section explains the task that you will perform.

Prepare for lift off
This section explains any preliminary work that you may need to do before beginning
work on the task.

Engage thrusters
This section lists the steps required in order to complete the task.

Objective complete – mini debriefing
This section explains how the steps performed in the previous section allows us to
complete the task. This section is mandatory.

Classified intel
This section provides some extra information relevant to the task.
You will also find a number of styles of text that distinguish between different kinds of
information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions,
pathnames, dummy URLs, user input, and Twitter handles are shown as follows: “We will
go through the important features of the pygame module, which is necessary to build our
arcade game, including playing sounds and controlling the menu.”
A block of code is set as follows:
GPIO.output(25, True)
while 1:
GPIO.output(25,False)
sleep(1)
GPIO.output(25,True)
sleep(1)

Any command-line input or output is written as follows:
# cp /usr/src/asterisk-addons/configs/cdr_mysql.conf.sample
/etc/asterisk/cdr_mysql.conf

New terms and important words are shown in bold. Words that you see on the screen, in
menus or dialog boxes for example, appear in the text like this: “clicking the Next button
moves you to the next screen”.

Note
Warnings or important notes appear in a box like this.

Tip
Tips and tricks appear like this.

Reader feedback
Feedback from our readers is always welcome. Let us know what you think about this
book—what you liked or may have disliked. Reader feedback is important for us to
develop titles that you really get the most out of.
To send us general feedback, simply send an e-mail to , and
mention the book title via the subject of your message.
If there is a topic that you have expertise in and you are interested in either writing or
contributing to a book, see our author guide on www.packtpub.com/authors.

Customer support
Now that you are the proud owner of a Packt book, we have a number of things to help
you to get the most from your purchase.

Downloading the example code
You can download the example code files for all Packt books you have purchased from
your account at http://www.packtpub.com. If you purchased this book elsewhere, you can
visit http://www.packtpub.com/support and register to have the files e-mailed directly to
you.

Downloading the color images of this book
We also provide you a PDF file that has color images of the screenshots/diagrams used in
this book. The color images will help you better understand the changes in the output. You
can download this file from
http://www.packtpub.com/sites/default/files/downloads/6227OT_ColoredImages.pdf.

Errata
Although we have taken every care to ensure the accuracy of our content, mistakes do
happen. If you find a mistake in one of our books—maybe a mistake in the text or the
code—we would be grateful if you would report this to us. By doing so, you can save
other readers from frustration and help us improve subsequent versions of this book. If
you find any errata, please report them by visiting http://www.packtpub.com/submiterrata, selecting your book, clicking on the errata submission form link, and entering the
details of your errata. Once your errata are verified, your submission will be accepted and
the errata will be uploaded on our website, or added to any list of existing errata, under the
Errata section of that title. Any existing errata can be viewed by selecting your title from
http://www.packtpub.com/support.

Piracy
Piracy of copyright material on the Internet is an ongoing problem across all media. At
Packt, we take the protection of our copyright and licenses very seriously. If you come
across any illegal copies of our works, in any form, on the Internet, please provide us with
the location address or website name immediately so that we can pursue a remedy.
Please contact us at  with a link to the suspected pirated
material.
We appreciate your help in protecting our authors, and our ability to bring you valuable
content.

Questions
You can contact us at  if you are having a problem with any
aspect of the book, and we will do our best to address it.

Chapter 1. Hello World
It is a Hotshot custom to begin learning anything new with a Hello World example. Since
we will be doing really cool things in this book, we will say “Hello World” in a unique
fashion. In this project, we will use the Raspberry Pi to cause an LED light to blink. This
project is directed towards those who are relatively new to the Raspberry Pi environment
as a warm-up exercise. Feel free to skip ahead if you have already done this with your Pi,
though we suggest you look through and make sure you haven’t missed anything.

A quick introduction to the Raspberry Pi
If we search for the term Raspberry Pi over the web or open the Raspberry Pi
Foundation’s webpage, we will find that the Raspberry Pi is a computer that is the size of
a credit card.

Parts of a Raspberry Pi

Features of a Raspberry Pi
The Raspberry Pi Foundation (http://www.raspberrypi.org/) initially released the
Raspberry Pi model B. This was followed by the Raspberry Pi model A. In 2014, the
Raspberry Pi foundation released variants B+ and A+. The Raspberry Pi models A and A+
(costing 25 USD and 20 USD respectively) do not come with an Ethernet port, a USB port
and 256 MB RAM. The model A+ replaced model A while the model B+ replaced model
B. The model B (price: 35 USD) came with an Ethernet port, 2 USB ports, and 512 MB
RAM; model B+, which supersedes model B, comes with 40 pin GPIO header as opposed
to 26 in the earlier models, and has 4 USB ports and a micro SD card slot instead of the
SD slot. Per the Raspberry Pi Foundation website, model B+ (as well as model A+)
consumes lower power, has better audio and a better form factor, which we certainly
concur with. The model A+ also comes with a 40 pin GPIO header and a micro SD card
slot. The models A+ and B+ have nine more GPIO pins than their predecessors.

Note
The Raspberry Pi 2 was released after we finished writing the book. Please refer to the
book’s site to find out more about getting started with model 2.
The objective of this book is to build cool projects using the Raspberry Pi. We will discuss
the components of Raspberry Pi from this perspective. If you are interested in finding out
more about the Raspberry Pi, the Raspberry Pi Foundation’s webpage has published the
technical specifications of all the components.
First, we will discuss the components available on the Raspberry Pi and the use of these
components in our projects. The components of the Raspberry Pi include:
2 USB ports (1 USB port available in model A)
Ethernet port (available only in models B and B+)
RCA output
HDMI output
Audio output
Low level peripherals, which include:
GPIO (General Purpose Input Output)
UART/Serial Port (Universal Asynchronous Receiver Transmitter)
I2C (two wire interface)
SPI (Serial Peripheral Interface)

Where can I buy a Raspberry Pi?
Element14 and RS Components are the most common distributors of the Raspberry Pi in
the United States. The Raspberry Pi model A was roughly priced at 25 USD, while its
successor model A+ was priced at 20 USD. The model B was priced at 35 USD and the
model B+ is priced at 40 USD. There are also an ever increasing number of local
distributors such as Adafruit and Fry’s Electronics in the US that sell the Raspberry Pi
for a margin. Please check the Raspberry Pi Foundation website and other sources for
more vendors.

Requirements to get started with the Raspberry Pi
In this section, we will discuss the items required to get started with the Raspberry Pi. We
will need all the same things that are required to use a computer/laptop. They are:
Display
Keyboard
Mouse
Wi-Fi Adapter / Ethernet cable

Note
It is possible to use the Raspberry Pi via remote login using a secure shell. This might
seem difficult to those who are new to the Linux environment. The setup of the Raspberry
Pi for remote login is explained in Project 13, Tips and Tricks.
The Raspberry Pi eLinux wiki (http://elinux.org/RPi_Hub) has listed peripherals that have
been tested and confirmed to have worked on the Raspberry Pi. You have the freedom to
choose peripherals according to your choice.
Display: The Raspberry Pi is provided with an HDMI output and an RCA output. It
is possible to connect a monitor that has an HDMI input. It is also possible to connect
monitors that have a DVI input with an HDMI to the DVI cable.
Power supply: Since the Raspberry Pi consumes 700 mA for its operation, it is
recommended that the reader uses powered USB hubs to use devices such as Wi-Fi
adapters as opposed to plugging in devices such as the Wi-Fi adapters directly to the
USB port of the Raspberry Pi to avoid the device resetting itself.

Operating systems on the Raspberry Pi
The Raspberry Pi foundation recommends the following operating systems on the
Raspberry Pi. They are:
Raspbian
Arch Linux ARM
RISC OS
You are welcome to choose any operating system of your choice. For beginners, we
strongly recommend the Raspbian OS for projects. The Raspbian is equipped with tools to
get started easily. The Raspberry Pi’s firmware is implemented such that the operating
system is loaded from an SD card.

Getting started with Raspbian
In this section, we will download an image from the Raspberry Pi Foundation’s webpage
to a computer, flash an SD card with the image, and set up the operating system on the
Raspberry Pi. We will also try to write and execute our first example.

Downloading Raspbian
The latest Raspbian image is hosted on the Raspberry Pi Foundation’s webpage
(http://www.raspberrypi.org/downloads/). The latest image at the time of writing this book
was Raspbian wheezy. We need to download the image and extract it to the folder of our
choice.

Raspbian wheezy on the Raspberry Pi Foundation’s website

Flashing image on to the SD card
We will discuss flashing the SD card with the Raspbian image on both Windows and
Linux machines.
Windows
Extract the files to a location of your choice. The Win32DiskImager tool is required to
prepare the SD card with the Raspbian image.

Tip
A standard Raspbian image is about 1.8 GB big. It is strongly recommended that you use
an SD card that is at least of 4 GB big.

The Win32DiskImager tool
We can flash the SD card in three simple steps (as shown in the preceding screenshot):
1.
2.
3.
4.

Select the SD card that needs to be flashed.
Select the Raspbian image location.
Click on Write.
Click on Yes to confirm.

Confirm overwriting the SD card
5. It can take a while before the write cycle is completed.

Linux

There are two identical methods to flash an SD card on a Linux machine. The two
approaches include:
A GUI-based approach
A command-line interface-based approach
A command-line interface-based approach

The SD card can be flashed in three simple steps using a command-line interface. These
steps are as follows:
1. Identify the SD card mount point.
2. Unmount the SD card.
3. Flash the SD card.
Identifying the SD card mount point

As soon as we insert the SD card into a USB card reader or an SD card slot found on a
laptop, we need to open a terminal on our Linux machine. We need to identify our device’s
mount point on the machine using the following command:
df –h

The devices enumerated on the machine will be listed as shown in the following
screenshot:

Storage devices identified by the operating system

Unmount the SD card

In the previous example, the /dev/sdb5 path is the storage device of interest. There may
be more than one storage device that might be connected to a machine. We need to make
sure that we have identified the right device. Once we have identified the device, it has to
be unmounted using the following command:
umount /dev/sdb
Flash the SD card

Now, we will flash our SD card using the following command:
dd bs=4M if=~/2012-09-18-wheezy-raspbian.img of=/dev/sdb

The if= argument points to the location of the image and of= refers to the SD card mount
point. The write operation takes a while to complete and it is ready for use on the
Raspberry Pi upon completion.
GUI-based approach

On a Debian Linux-based operating system, there is a package called usb-imagewriter.
The ImageWriter package performs the same operations required to flash an SD card.

A USB ImageWriter on Ubuntu

Setting up the Raspberry Pi
Now that the image is flashed, let’s get started with setting up the Raspberry Pi for the first
time. We will have to insert the SD card slot found on the other side of the Raspberry Pi.

A flashed SD card in the slot
When the keyboard and the mouse are connected, we can get started by powering up the
Raspberry Pi!
Once the Raspberry Pi is powered up, the operating system boots up to Raspi-config. The
raspi-config is the tool used to set up desktop options, keyboard settings, storage
settings, and so on. The Raspi-config screen is shown in the following screenshot:

The Raspi-config screen

In this section, we will discuss each feature of the raspi-config tool:
info: As the name suggests, this section gives the general information about the tool.
expand_rootfs: While the SD card is flashed with the operating system image, the

SD card is partitioned just about the size of the image. This command aids to expand
the partition so that the remaining space can be used for file storage.
overscan: This is an option used when the Raspberry Pi is connected to the
television.
configure_keyboard: This option is used to configure the change_type option of the
keyboard.
change_pass: The default password is raspberry, and if necessary, this option lets
you switch to a stronger password.
change_locale: The option lets you change the language preferences.
change_timezone: We can set our current time zone using this option.
memory_split: This option lets us split the memory between the ARM processor’s
CPU and the graphics processor.
overclock: The default clock speed is 700 MHz. This option lets you set the clock
speed to 1 GHz. This might vary for Raspberry Pi 2.
ssh: This option enables the secure shell server. This is required to remotely log in
the Raspberry Pi and control devices remotely. It is enabled by default on Raspbian.
boot_behaviour: This option enables you to boot directly into the desktop.

Tip
It is important that you enable this option on as the default option boots into a normal
text-based console.
update: If the Raspberry Pi is connected to the Internet using an Ethernet
raspi-config tool downloads any package that might be available.

cable, the

Once we complete the setup process by selecting Finish, the Raspberry Pi reboots and
expands the filesystem if necessary.

Mission briefing
In this project, we will set up the GPIO (General Purpose Input Output) peripheral on
the Raspberry Pi and write our first program to cause an LED to blink. At the end, we will
repeat the same steps with a Raspberry Pi add-on board called PiCrust. This will allow
you to get your feet wet and ensure you have all the right tools going forward, and should
you need to, troubleshoot any problems you might identify.

Why is it awesome?
Think of saying “Hello World” as both a nod to programming tradition and a dry run to
ensure you are well equipped!

Your Hotshot objectives
The objectives for this mission are quite simple, and yet take us all several milestones
further! Here are the objectives of the Hello World mission:
Collect all the necessary tools
Set up the GPIO peripheral
Introduce ourselves to the Raspberry Pi environment
Turn a light emitting diode (LED) on and off with a 1 second delay

Mission checklist
Go over the previous sections, and make sure you have all the tools. Download the GPIO
libraries, and ensure you can log in to the Raspberry Pi remotely, and you are all set!

Note
There are two different ways to use a Raspberry Pi. They are:
Connecting a monitor to the HDMI port or the RCA jack and a keyboard to the USB
port of the Raspberry Pi.
Remotely logging into the Raspberry Pi from the reader’s workstation.
If you are a beginner, it is best to use the first method while the second method can be
used if you are familiar with the Linux operating system and remote login capabilities.
Once we complete the setup process by selecting Finish, the Raspberry Pi reboots and
expands the file system if necessary.

Hunting and gathering
As stated before, you will need to make sure you have all the tools. So, go ahead, hunt and
gather away. Grab at least one of each of the following and more than one of each, if you,
like us, are prone to accidents:
A laptop to download the Raspberry Pi image and set up everything
Raspberry Pi—Model B/B+ (preferred), a keyboard, and a mouse for the Raspberry
Pi (optional)
SD card with 4GB memory (SD card preparation was explained earlier in this
project)
USB Power Adapter (Rated 1.0 A) and Micro USB power cable
Ethernet cable
Wi-Fi adapter—(optional) refer to the eLinux wiki for Raspberry Pi for verified
peripherals
Breadboard
Jumper wires
Discrete Resistor Values
A work bench (or a clean working surface—hopefully you have one)
Good thoughts and a can-do attitude
Lots of coffee, tea, or a safe beverage of your choice

Engage thrusters
You will need all of the tools listed in the previous section to get through this project. Take
your time and make sure you have everything handy!

Objective complete – mini debriefing
Do you have all the tools? Ready to go? Then on to the next task!

Setting up the GPIO
We need to enable the GPIO peripherals in our Raspbian installation to get started. In
order to download the required tools and set things in motion, the Raspberry Pi needs to be
connected to the Internet.
The GPIO pin is a pin that is available from the Raspberry Pi’s processor that enables
interfacing input and output devices to the Raspberry Pi. In this section, we will talk about
setting up the GPIO for interfacing an output device. There is a 26-pin interface (40 in
Model B+) available on the Raspberry Pi and about 17 of those 26 pins are GPIO pins (26
of them in Model B+) while the others are miscellaneous pins such as power. The pins are
driven by a 3.3 V rail and each GPIO pin is rated for about 17 mA and the total current
draw not exceeding 50 mA.

Engage thrusters
We also need to know the GPIO peripherals available to conduct our experiment. The
following figure shows the GPIO maps of the Raspberry Pi Rev 1 and Rev 2:

GPIO map for Models A, B, and B+. (Image published with permission from Raspi.tv)
The letter P1 shown in the following image corresponds to P1-1 of the GPIO map. P1-1
corresponds to the first pin on the left in the front row, while P1-2 corresponds to the first
pin on the left in the back row.

The Raspberry Pi GPIO peripheral

In this book, we will be mostly using Python programming language. Python is a very
simple and easy language to learn. We may wander off to other programming languages
from time to time, but we will mostly stick to Python. With this in mind, let’s get started.

Installing GPIO libraries
There are a lot of libraries available to access the GPIO peripheral. The easiest to install
and use is the quick2wire python API. The API is used to control the GPIO peripherals
and I2C devices connected to the Raspberry Pi.

Note
There are different libraries such as the RPi.GPIO, Pi4J, and so on. We are using the
quick2wire API in this example as a beginner might find it easy to use. You are welcome
to use other libraries of your choice. The quick2wire-gpio-admin tool enables controlling
the GPIO pins without root access.
One disadvantage of using the quick2wire module is that it provides access only to GPIO
pins 0 through 7.
The terminal can be located in the left corner of the desktop and has been highlighted in
the following screenshot:

A Command-line terminal on the Raspbian desktop
1. The quick2wire library installation is based on a post on the quick2wire website
(http://quick2wire.com/articles/how-to-add-quick2wire-as-a-raspbian-software-

source/). In order to install the quick2wire-python library, the repository needs to be
added to /etc/apt/sources.list.
In the command line, the repository is added by using the nano text editor:
sudo nano /etc/apt/sources.list

The following lines need to be added to the file:
# Quick2Wire Software
deb http://dist.quick2wire.com/raspbian wheezy main
deb-src http://dist.quick2wire.com/raspbian wheezy main

The file can be saved by typing CTRL+X. The file can also be saved by pressing
Y key while exiting the editor.
Alternatively, the lines can be added using a graphical text editor such as,
leafpad and saving it:
sudo leafpad /etc/apt/sources.list

2. In order to ensure that the packages are downloaded from the quick2wire repository,
we need to authenticate the packages using a key available from quick2wire:
wget https://raw.githubusercontent.com/quick2wire/quick2wire-softwareusers/master/software@quick2wire.com.gpg.key
sudo apt-key add
software@quick2wire.com.gpg.key

3. The cache is updated and the latest software packages can be downloaded as follows:
sudo apt-get update
sudo apt-get upgrade

4. The quick2wire tool is installed as follows:
sudo apt-get install quick2wire-gpio-admin
sudo apt-get install quick2wire-python3-api

Objective complete – mini debriefing
Now, wasn’t that easy? Let’s get more familiar with the GPIO input/output operations.

GPIO programming using Python
In this section, we will ensure that the library is correctly installed and add the user to the
group. This will enable the user to use the GPIO pins without having root privileges. This
will be followed by the section on getting started with GPIO control programming in
Python.

Engage thrusters
In order to get started with programming in the Raspberry Pi, we will launch Python
IDLE3 from the desktop.

Launching IDLE3 from the desktop
1. Now, we have to get started with programming the LED blinking example in IDLE3.
2. This LED blinking sample code is as follows:
from time import sleep
from quick2wire.gpio import pins, Out
with pins.pin(7, direction=Out) as out_pin:
while True:
out_pin.value = 1
sleep(1)
out_pin.value = 0
sleep(1)
out_pin.unexport()

3. We will import the sleep class from the time module in the first line. This is required
to introduce a 1-second delay between turning the LED on and off every other
second:
from time import sleep

4. We also need the pin class from the quick2wire GPIO library:

from quick2wire.gpio import Pin

5. We need to set the output pin that we will be using in the example:
LED_output = Pin(8, Pin.Out)

6. We can set the pin to the logical high (3.3 V) as follows:
LED_output=1

7. We will set the pin to the logical low (0 V) as follows:
LED_output=0

8. We will execute the same thing using an infinite while loop:
while True:
LED_output=1
sleep(1)
LED_output=0
sleep(1)

9. This will make the LED blink with a 1-second delay. We should also note the indent
on the blink sequence. The blink sequence has a different indent compared to the
while loop. Hence, the code that is at a different indent is executed infinitely.
10. When the program is interrupted (by pressing CTRL + C on the keyboard), we need
to unexport the pins at exit:
out_pin.unexport()

An alternative to quick2wire – RPi.GPIO
1. Another alternative is to use RPi.GPIO (https://pypi.python.org/pypi/RPi.GPIO). It
comes as a standard package along with the Raspbian Wheezy OS. Let’s perform a
quick review of the code:
import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BCM)
GPIO.setup(8,GPIO.OUT)
GPIO.output(8,GPIO.LOW)
while True:
GPIO.output(8,GPIO.HIGH)
sleep(1)
GPIO.output(8,GPIO.LOW)
sleep(1)
GPIO.cleanup()

2. After importing the required modules, we get started with setting up the pin
numbering mode. There are two types of pin numbering modes, namely:
The BCM Pin numbering mode: The pin numbers are based upon the pin

numbers of the BCM chip.
The Board numbering mode: The pin numbers are based upon the pin
numbers of the Raspberry Pi GPIO header.
In this example, we will set the BCM numbering mode and set pin 8 as the
output:
GPIO.setmode(GPIO.BCM)
GPIO.setup(8,GPIO.OUT)

3. We can set the pin to logical high (3.3 V) as follows:
GPIO.output(8,GPIO.HIGH)

4. We can set the pin to logical low (3.3 V) as follows:
GPIO.output(8,GPIO.LOW)

5. Now, the LED can be made to blink with a 1 second delay:
while True:
GPIO.output(8,GPIO.HIGH)
sleep(1)
GPIO.output(8,GPIO.LOW)
sleep(1)

6. When the program is interrupted by typing CTRL + C, we have to clean up and
release any occupied GPIO resources:
GPIO.cleanup()

Objective complete – mini debriefing
In this section, we finished writing a program to make an LED blink. In the next section,
we will put a circuit together that makes an LED blink.

Electrical output of our program
In the previous section, we wrote a program to make an LED blink. Let’s look at the
electrical connection to observe the output of our program. We will connect a resistor
between the GPIO pin and the anode of the LED. We will connect the cathode to the
ground pin of the Raspberry Pi.

Engage thrusters
We will connect the LED and the resistor to the GPIO pin and the ground pin, as shown in
this image:

LED blinking circuit

Note
If we are not careful with the handling of the Raspberry Pi GPIO pins, it may either
temporarily reset the Raspberry Pi or sometimes even permanently damage the GPIO pin.
There are several tutorials in basic electronics available over the Web. It is important that
you familiarize yourself with the basics of electronics.
Once we connect the circuit as shown in the preceding image, we will be able to execute
the program and conclude our experiment.
We can execute the program by running the module, as shown in the following screenshot:

Executing the Python example

Objective complete – mini debriefing
That’s it! We have wet our feet by saying Hello World by blinking an LED! On our way to
bigger and better things, let’s stop and examine the Pi Crust for a moment.

Introduction to the Pi Crust – a prototyping platform for the Raspberry
Pi
Now that our Hello World example is done, we will leave you with one more thing.
Throughout this book, we will review some add-on hardware to access the GPIO
peripherals on the Raspberry Pi. In this project, we will discuss the Pi Crust board for the
Raspberry Pi.
The Pi Crust board was designed by Joe Walnes. It is a board that is stackable on the
Raspberry Pi and eliminates the need for a breadboard to prototype circuits.

A Pi Crust board
The Pi Crust is an open source add-on hardware and costs approximately $14 to build one
ourselves. The design can be downloaded free of cost from http://picru.st.
So, it is up to you to decide whether you want to simply buy one, build one, or as we are

prone to encourage, improve upon it and open source it for others to benefit!
The main advantage behind Pi Crust is that it is aids prototyping. It allows easy access to
the I2C interface, SPI interface, UART port, and the GPIO pins. The following figure
shows BlinkM—an I2C-driven RGB LED mounted on top of the Pi Crust.

Pi Crust stacked on top of the Raspberry Pi

Mission accomplished
Now that you have traveled this far with us, how do you feel? Do you need a break, or
more coffee? Before you do either, let’s review.
In this project, we got started with the LED blinking example using the Raspberry Pi. We
discussed the setup of GPIO peripherals and using them in an experiment. You are
welcome to continue experiments with the GPIO peripherals with projects such as LED
sequencing, three bit counter, and so on.
In the forthcoming projects, we will look into I2C communication, SPI communication,
and UART communication (serial port).

Hotshot challenge
Well done; you have taught your Pi to say “Hello World”! However, we are sure you can
do more, much more. Have you watched the movie Close Encounters of the Third Kind?
Well, if not, you should. However, this is not a challenge in itself. In the movie, the human
beings attempt at communication with what they believe is aliens by building a pattern of
lights that are set to music. Can you make a pattern of LEDs repeat that or something
similar?

Chapter 2. A Raspberry WebIDE
Example
In this project, we will learn how to develop projects using the WebIDE from Adafruit
Industries. We will flash an SD card with the Raspbian OS, install the Occidentalis tool
(https://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/occidentalis-v0dot-3), set up the web-based development tool, and test the setup using an example.

Note
Occidentalis was initially available as a Raspbian OS image by Adafruit Industries. It
comprised of the toolset that enabled to get started with project development using the
Raspberry Pi. The OS image was deprecated and released after we finished writing the
book. We have taken our best effort to update the book. Please refer to this book’s website
for more information.

Mission briefing
In this project, we will discuss installing a tool, Occidentalis, and a WebIDE that enables
programming in the Python language on the Raspberry Pi. We will also discuss one
example from the Adafruit repository and another example of driving an RGB LED.
The following table lists the bill of materials used in this project. These are just examples,
and alternative products that have a similar specification may also be used.
Item

Estimated Cost

Raspberry Pi Model B

35 USD

Adafruit Cobbler (https://www.adafruit.com/product/914)

7 USD

Adafruit 7-segment LED Backpack (https://www.adafruit.com/product/879) 10 USD
Blinkm (https://www.sparkfun.com/products/8579)

13 USD

Why is it awesome?
The Adafruit WebIDE in combination with the Occidentalis operating system enables
development in the Python language on a Raspberry Pi using just a web browser. It also
enables access to sample projects developed by Adafruit via Bitbucket, a source control
tool. (If you are not familiar with source control tools such as Bitbucket, Git, and so on,
the examples in this project are a great way to get started!) The Adafruit WebIDE is a tool
developed for hobbyists and comes with examples for techniques such as pulse-width
modulation (used in lighting system control) and I2C communication, and also provides
examples for controlling products from Adafruit.

Note
The Adafruit WebIDE is now a beta release and it may not work successfully across
different platforms. The Adafruit learning system has indicated that this development tool
was directed towards advanced hobbyists. We have taken our best efforts to explain it as
simply as possible.
Pulse-width modulation is a technique used widely in motor control, lighting systems, and
so on. It is a technique where the average voltage applied to a device is varied by changing
the width of the pulse. There are several tutorials on pulse-width modulation
(https://learn.sparkfun.com/tutorials/pulse-width-modulation) available all over the Web.
I2C communication (https://learn.sparkfun.com/tutorials/i2c) is a form of serial
communication interface used to connect multiple slave devices (usually sensors) with a
master device (Raspberry Pi or a microcontroller) through a common interface.

Your Hotshot objectives
In this project, we will discuss the following features:
Bootstrapping your Raspberry Pi by installing Occidentalis
Setup of remote login into the Raspberry Pi
Installation of the Raspberry Pi WebIDE
Python development on the WebIDE
Test and debugging examples using the WebIDE

Note
This project should not be considered as an attempt to promote Adafruit Industries or
their products developed for their platform. This project merely demonstrates
simplification of development on the Raspberry Pi using a tool from Adafruit
Industries.

Mission checklist
In order to get started, the first step is to install the Occidentalis distro, which is a
derivative of the Raspbian operating system.
The things required to get started are as follows:
A 4 GB SD card flashed with the Raspbian OS
An Occidentalis image.
An Ethernet cable

Installation, features, and usage of the
Occidentalis operating system from
Adafruit
The first step is installing Occidentalis on the Raspberry Pi.

Prepare for lift off
The first step is the installation of the Adafruit-Pi-Finder tool. The tool can be downloaded
from https://github.com/adafruit/Adafruit-Pi-Finder/releases/latest. It is available for
Windows, Linux, and Mac platforms.

Engage thrusters
1. You can find detailed instructions on installing the Occidentalis tool at
https://github.com/adafruit/Adafruit-Pi-Finder.
2. Alternatively, a step-by-step instruction is also available on this book’s website. We
cannot include them here since changes were made to Occidentalis installation
process after we finished writing this book.

Objective complete – mini debriefing
Once the installation is complete, we have to ensure that the Raspberry Pi as well as the
development machine are connected to the network via the Ethernet port or a USB Wi-Fi
dongle.

Setup of a remote login into the Raspberry
Pi
In this section, we will remotely log in to the Raspberry Pi using a secure shell. Since the
Raspberry Pi comes with sshd enabled, it is possible to log in remotely using the local
name, raspberrypi.local (During the bootstrapping process, the avahi-daemon tool is
installed and hence, it is possible to remotely log in to the Raspberry Pi using the local
name, raspberrypi.local). Alternatively, on a Windows machine, you can use a tool
such as Advanced IP Scanner (http://www.advanced-ip-scanner.com/) to find the IP
address of the Raspberry Pi. A snapshot of this tool is shown later in this project.

Note
If you are using a Windows machine, the Bonjour Print Services drivers have to be
installed to remotely log in using the local name, raspberrypi.local. The Bonjour Print
Services drivers are available from http://support.apple.com/kb/DL999.

Prepare for lift off
The IP address of the Raspberry Pi can be identified using tools such as Advanced IP
Scanner, as shown in the following screenshot:

A list of devices and IP addresses connected to a network similar to the Raspberry Pi

Engage thrusters
1. Once we know the IP address, we use an SSH client such as PuTTY on Windows or a
command-line terminal on a Linux or a Mac machine to remotely log in to the
machine (in this case, we show this on a Windows machine).
2. On a Windows machine, we either use the IP address of the Raspberry Pi or its local
name (raspberrypi.local) and log in to the Raspberry Pi, as shown in the following
screenshot:

3. Once we enter the IP address / local name in the PuTTy window, we log in as
follows:
login as: pi
@'s password: raspberry

Alternatively, we can also log in using the IP address of the Raspberry Pi instead of
the local name, raspberrypi.local.

Objective complete – mini debriefing
If the username and password are entered correctly, we should be able to remotely log in
to the Raspberry Pi to install the web server.

Installation of the Raspberry Pi WebIDE
We will get started by using a remote login client such as PuTTY to remotely log in to the
Raspberry Pi and install the Adafruit WebIDE. In order to get started with examples from
the Adafruit repository, we need a Bitbucket account, and Adafruit provides detailed
instructions for this at http://learn.adafruit.com/webide/getting-started.

Engage thrusters
1. Once we have logged in, the Adafruit learning system’s website recommends
executing the following to install the web server:
curl https://raw.githubusercontent.com/adafruit/AdafruitWebIDE/master/scripts/install.sh | sudo sh

2. It should take about five minutes to finish the installation. If the installation was
successful, we should be able to see the message marked in the following screenshot:

Successful completion of the Adafruit WebIDE installation
3. Assuming the installation was successful, we should be able to launch the Adafruit
WebIDE using http://raspberrypi.local.

Adafruit WebIDE launched for the first time
4. In order to make use of the examples from Adafruit Industries, we need to create a
Bitbucket account (it is possible to create one with a Google account) and integrate
the WebIDE with the Bitbucket account. The instructions for this are provided on the
web page, as shown in the preceding screenshot.

Objective complete – mini debriefing
If the installation was successful, after completion of the registration, we are done with
this task. Let’s move on and learn to code using the WebIDE!

Python development on the WebIDE
In this section, we will use a 7-segment LED backpack and the Adafruit Cobbler along
with a 26-pin ribbon cable. We will test an example from the Adafruit repository
(https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code). In this project, the new
add-on hardware that we will discuss is the Adafruit Cobbler. The Cobbler is a small
board that aids prototyping circuits on a breadboard. The Adafruit Cobbler costs about 7
USD while the ribbon cable costs about 3 USD and the 7-segment backpack costs about
10 USD.

Note
The earlier mentioned products are merely examples to demonstrate the Adafruit WebIDE.
There are alternative prototyping platforms and products available for a higher or lower
price.

The Cobbler mounted on a breadboard

Prepare for lift off
In order to get started with the prototyping, the 26-pin ribbon cable is used to connect the
GPIO interface to the Cobbler, as shown in the following image. We have to ensure that
pin 1 of the GPIO header matches pin 1 of the Adafruit Cobbler. (The Cobbler comes with
a shrouded header, and hence it is foolproof. However, pin 1 of the Raspberry Pi needs to
be matched correctly.)

Quick introduction to the I2C interface
The I2C interface was invented by Phillips Semiconductors. It is a form of serial
communication interface used to connect multiple slave devices (usually sensors) with a
master device (Raspberry Pi or a microcontroller) through a common interface. Each
device has a unique address that is used by the master to read or write data. There are
plenty of resources available to familiarize ourselves with the I2C interface. We will move
on to the next stage of configuring the interface.

Configuring the I2C interface on the Raspberry Pi
In the Occidentalis distribution, the I2C drivers are installed and enabled by default.
Hence, we can get started by connecting the Adafruit 7-segment backpack to the Adafruit
Cobbler, as shown in the following image. (Connections between the Cobbler and the 7segment backpack are Clock pin, SCL (C)-SCL(B) Data Pin - SDA(C) -SDA(B), 3V3(C)
to +(B) GND(C) to -(B), where C is the Cobbler and B is the backpack):

7-segment backpack connections on a breadboard
Now that we have connected the Raspberry Pi, the Adafruit Cobbler, and the 7-segment
backpack, let’s get started with the detection of the backpack on the Raspberry Pi’s I2C
interface and program an example.
Before we get started with the example, we need to determine the I2C bus to which the
device is connected by using the following command:
sudo i2cdetect –y 0

The command outputs a table that contains the list of devices for that particular bus. Since
there are no devices connected to bus 0, we scan for devices on bus 1. In this experiment,
we are testing the Adafruit 7-segment backpack. In the figure that follows, the 7-segment
backpack is connected to bus 1 and the device address is 0x70. Refer to the following
screenshot:

The i2cdetect output
We should change the bus address in the code to drive the 7-segment backpack. Line 11 in
the Adafruit_I2C.py file needs to be changed in the code according to the bus to which
the device is connected. Hence, line 11 should be:
def __init__(self, address, bus=smbus.SMBus(1), debug=False):

Engage thrusters
1. The 7-segment backpack is a device controlled via an I2C port. Any I2C device has
four pins, namely clock, data, power supply, and ground. The I2C device needs to be
connected to the Cobbler, as shown in the earlier screenshot.
2. There are several examples available from Adafruit in the WebIDE. Let’s locate the
ex_7segment_clock.py example (in the IDE, it is located at Adafruit_RaspberryPi-Python-Code | ex_7segment_clock.py). This is a simple example to display the
current time on the 7-segment backpack:

The ex_7segment_clock.py file location in the WebIDE
3. Let’s do a quick review of the program. We get started by importing the datetime
and Adafruit_7Segment modules:
The segment variable is initialized as an instance of an I2C device at the address
0x70. We enter an infinite loop and get the current time using the datetime
module:
now = datetime.datetime.now()
hour = now.hour
minute = now.minute
second = now.second

Since the 7-segment LED backpack consists of four digits, we write the current
time at each position as follows along with a colon:
# Set hours
segment.writeDigit(0,
segment.writeDigit(1,
# Set minutes
segment.writeDigit(3,
segment.writeDigit(4,

int(hour / 10))
hour % 10)

# Tens
# Ones

int(minute / 10))
minute % 10)

# Tens
# Ones

# Toggle colon
segment.setColon(second % 2)
# Wait one second

# Toggle colon at 1Hz

This exercise is repeated with a one second interval.
4. The program is executed by clicking on Run found in the IDE. If our connections
were right, we should be able to see the current time on the 7-segment display
(shown in the following figure).

Objective complete – mini debriefing
We were able to test an Adafruit product using their WebIDE in this section.

A 7-segment backpack connected to the Cobbler

Test and debugging examples using the
WebIDE
In this example, we will connect the BlinkM to the Raspberry Pi. A BlinkM is an RGB
LED that can be connected to your Raspberry Pi via the I2C interface. It is possible to
execute light scripts using the port. The connections to the BlinkM are similar to that of
the 7-segment backpack.

BlinkM connected to the Cobbler

Note
It is important to pay attention while connecting devices to the GPIO header of the
Raspberry Pi. If there are devices that draw a lot of current from the GPIO pins, it may
reset the Pi or permanently damage it in the event of a short circuit. It is assumed that you
are familiar with basic electronics and capable of handling such devices.

Prepare for lift off
Similar to the previous experiment, we need to determine the bus to which the device is
connected using the i2cdetect command. As shown in the following screenshot, the
device is connected to bus 1 and the device address is 0x09:

Blinkm connected to bus 1

Engage thrusters
1. The BlinkM datasheet
(thingm.com/fileadmin/thingm/downloads/BlinkM_datasheet.pdf) provides step-bystep information to execute the light scripts.
2. A list of scripts available on the BlinkM is shown in the following screenshot:

A list of scripts available on the BlinkM
3. Let’s see the code to execute a light script (for example, script number 6) on the
BlinkM using the Adafruit WebIDE interface. In order to execute a script forever, the
datasheet mentions that the following characters should be written at the I2C device
address in the following sequence: 'p',