Python Programming with Raspberry Pi

Python Programming with Raspberry Pi

Build small yet powerful robots and automation systems with Raspberry Pi Zero

Sai Yamanoor

Srihari Yamanoor

       BIRMINGHAM - MUMBAI

Python Programming with Raspberry Pi

Copyright © 2017 Packt Publishing

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First published: April 2017

Production reference: 1260417

Published by Packt Publishing Ltd.

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ISBN 978-1-78646-757-7

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Credits

About the Authors

Sai Yamanoor is an embedded systems engineer working for a private startup school in the San Francisco Bay Area, where he builds devices that helps students achieve their full potential. He completed his graduate studies in Mechanical Engineering at Carnegie Mellon University, Pittsburgh PA, and his undergraduate work in Mechatronics Engineering from Sri Krishna College of Engineering and Technology, Coimbatore, India. His interests, deeply rooted in DIY and ppen 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 the Raspberry Pi, Arduino, Galileo, Android devices and others. Sai blogs about his adventures with Mechatronics at the aptly named Mechatronics Craze blog at http://mechatronicscraze.wordpress.com/. You can find his project portfolios at http://saiyamanoor.com.

This book is Sai's second title and he has earlier published a book titled Raspberry Pi Mechatronics Projects.

I would like to thank my parents for encouraging me in all my endeavors and for making me what I am today. I am thankful to my brother who has helped me shape my career all these years. I would like to sincerely apologize to Balaji Raghavendra for the mixup with the first book and sincerely thank him for his reviews and advice on the first book. I am also thankful to the team at Packt, especially Abhishek who was patient and understanding under trying circumstances.

Srihari Yamanoor is a mechanical engineer, working on medical devices, sustainability, and robotics in the San Francisco Bay Area. He completed his graduate studies in Mechanical Engineering at Stanford University, and his undergraduate studies in  Mechanical Engineering from PSG College of Technology, Coimbatore, India. He is severally certified in SolidWorks, Simulation, Sustainable Design, PDM as well as, in quality and reliability engineering and auditing. His interests have a wide range, from DIY, crowdfunding, AI, travelling, and photography to gardening and ecology. In his spare time, he is either traveling across California, dabbling in nature photography, or at home, tinkering with his garden and playing with his cats.

I have many people to thank for any and all success in my life, one of the culminations being this second book. I start with my parents for always making sure that I put my career and education first. My brother Sai Yamanoor, is the main reason I have my name on not one, but two books! I have to thank several professors and teachers, not the least of whom are Kenneth Waldron, Dr. Radhakrishnan, Dr. R. Rudramoorthy, Dr. K.A. Jagadeesh, Cyril Master, and the Late Master Williams. Of course, I'd be remiss, if I didn’t acknowledge my mentors, Russ Sampson, James Stubbs, Mukund Patel, and Anna Tamura. Then, I have my dearest friends, Patrick Nguyen, Anna Jao, Andrew Eib, Vishnu Prasad Ramachandran, and David Ma, who have put up with my quirks over the last several years, patiently offering advice and helping me weather several storms. I too would like to apologize to Balaji Raghavendra, who was left out of the acknowledgements from our last book, purely by accident, and nevertheless, inexcusably so. Without your help, we would not have been able to complete that book and start on this one. I second Sai in recognizing Abhishek Jadhav’s immeasurable patience and guidance throughout the course of the publication of this book.  Last but not the least, there are my beloved felines, the glaring that keeps me going – Bob, Gi-Ve, Fish Bone and Saxi.

We would like to acknowledge that 100% of the proceeds in revenue and profits of the authors, is being turned over to worthy non-profits.

About the Reviewer

Ian McAlpine had his first introduction to computers was his school's Research Machines RML-380Z and his physics teacher's Compukit UK101. That was followed by a Sinclair ZX81 and then a BBC Micro Model A, which he still has to this day. That interest resulted in a MEng degree in Electronic Systems Engineering from Aston University and an MSc degree in Information Technology from the University of Liverpool. Ian is currently a Senior Product Expert in the BI & Analytics Competence Centre at SAP Labs in Vancouver, Canada.

The introduction of the Raspberry Pi rekindled his desire to tinker, but also provided an opportunity to give back to the community. Consequently Ian was a very active volunteer for 3 years on The MagPi, a monthly magazine for the Raspberry Pi, which you can read online or download for free at http://www.raspberrypi.org/magpi/. He also holds an amateur radio license (callsign VE7FTO) and is a communications volunteer for his local community Emergency Management Office. He was a technical reviewer for Packt books, such as Raspberry Pi Cookbook for Python Programmers, Raspberry Pi Projects for Kids, and Raspberry Pi 2 Server Essentials.

I would like to thank my darling wife, Louise, and my awesome kids Emily and Molly for allowing me to disappear into my office…and for training our dog to fetch me!

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Table of Contents

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

Getting Started with Python and the Raspberry Pi Zero

Let's get started!

Things needed for this book

Buying the Raspberry Pi Zero

Introduction to the Raspberry Pi Zero

The features of the Raspberry Pi Zero

The setup of the Raspberry Pi Zero

Soldering the GPIO headers

Enclosure for the Raspberry Pi Zero

OS setup for the Raspberry Pi

micro SD card preparation

Let's learn Python!

The Hello World example

Setting up your Raspberry Pi Zero for Python programming

IDLE's interactive tool

The text editor approach

Launching the Python interpreter via the Linux Terminal

Executing Python scripts using the Linux Terminal

The print() function

The help() function

Summary

Arithmetic Operations, Loops, and Blinky Lights

Hardware required for this chapter

Arithmetic operations

Bitwise operators in Python

Logical operators

Data types and variables in Python

Reading inputs from the user

The formatted string output

The str.format() method

An exercise for the reader

Another exercise for the reader

Concatenating strings

Loops in Python

A for loop

Indentation

Nested loops

A while loop

Raspberry Pi's GPIO

Blinky lights

Code

The applications of GPIO control

Summary

Conditional Statements, Functions, and Lists

Conditional statements

An if-else statement

if-elif-else statement

Breaking out of loops

The applications of conditional statements: executing tasks using GPIO

Breaking out a loop by counting button presses

Functions in Python

Passing arguments to a function:

Returning values from a function

The scope of variables in a function

GPIO callback functions

DC motor control in Python

Some mini-project challenges for the reader

Summary

Communication Interfaces

UART - serial port

Raspberry Pi Zero's UART port

Setting up the Raspberry Pi Zero serial port

Example 1 - interfacing a carbon dioxide sensor to the Raspberry Pi

Python code for serial port communication

I2C communication

Example 2 - PiGlow

Installing libraries

Example

Example 3 - Sensorian add-on hardware for the Raspberry Pi

I2C drivers for the lux sensor

Challenge

The SPI interface

Example 4 - writing to external memory chip

Challenge to the reader

Summary

Data Types and Object-Oriented Programming in Python

Lists

Operations that could be performed on a list

Append element to list:

Remove element from list:

Retrieving the index of an element

Popping an element from the list

Counting the instances of an element:

Inserting element at a specific position:

Challenge to the reader

Extending a list

Clearing the elements of a list

Sorting the elements of a list

Reverse the order of elements in list

Create copies of a list

Accessing list elements

Accessing a set of elements within a list

List membership

Let's build a simple game!

Dictionaries

Tuples

Sets

OOP in Python

Revisiting the student ID card example

Class

Adding methods to a class

Doc strings in Python

self

Speaker controller

Light control daemon

Summary

File I/O and Python Utilities

File I/O

Reading from a file

Reading lines

Writing to a file

Appending to a file

seek

Read n bytes

r+

Challenge to the reader

The with keyword

configparser

Challenge to the reader

Reading/writing to CSV files

Writing to CSV files

Reading from CSV files

Python utilities

The os module

Checking a file's existence

Checking for a folder's existence

Deleting files

Killing a process

Monitoring a process

The glob module

Challenge to the reader

The shutil module

The subprocess module

The sys module

Summary

Requests and Web Frameworks

The try/except keywords

try...except...else

try...except...else...finally

Connecting to the Internet - web requests

The application of requests - retrieving weather information

The application of requests - publishing events to the Internet

Flask web framework

Installing Flask

Building our first example

Controlling appliances using the Flask framework

Summary

Awesome Things You Could Develop Using Python

Image processing using a Raspberry Pi Zero

OpenCV

The verification of the installation

A challenge to the reader

Installing the camera to the Raspberry Zero

Speech recognition

Automating routing tasks

Improving daily commute

A challenge to the reader

Project challenge

Improving your vocabulary

A challenge to the reader

Project challenge

Logging

Threading in Python

PEP8 style guide for Python

Verifying PEP8 guidelines

Summary

Lets Build a Robot!

Components of the robot

Setting up remote login

Changing the password

Enabling SSH access

Chassis setup

Motor driver and motor selection

Preparing the motor driver circuit

Raspberry Pi Zero and motor driver assembly

Raspberry Pi Zero and motor driver assembly

Robot Power supply setup

Setting up the motor power supply

Using the Raspberry Pi Zero's 5V power supply

Using an external power supply

Testing the motors

Motor driver detection

Detecting motor driver

Motor test

Dependencies

Camera setup

Verification of camera function

The web interface

Camera setup for the web interface

Buttons for robot control

Troubleshooting tips

Project enhancements

Summary

Home Automation Using the Raspberry Pi Zero

Voice activated personal assistant

Installing requisite packages

How does it work?

Setting up the audio tools

Connecting the speaker

Connecting the microphone

Houndify

Building voice commands

Adding a button

Web framework based appliance control/dashboard

Building the web dashboard

Personal Health Improvement—Sitting is the new smoking

Installing requisite software packages

Getting access keys for Fitbit client

Fitbit API Test

Building the visual aid

Smart lawn sprinkler

Summary

Tips and Tricks

Change your Raspberry Pi's password

Updating your OS

Setting up your development environment

SSH access via Windows

SSH access via Linux/macOS

Transferring files to/from your Pi

WinSCP

Mac/Linux environment

Git

Command-line text editors

Graphical text editors

SSH aliases (on Mac/Linux Terminals)

Saving SSH sessions on PuTTY

VNC access to Raspberry Pi

The RUN switch of the Raspberry Pi Zero board

GPIO pin mapping

Stackable breadboard

Summary

Preface

The Raspberry Pi represents the best in innovation in computer science, education, entertainment, hobby hacking, and several other categories that you can classify the device family into. Even as this book is entering publication, the Raspberry Pi family of products have become the third best selling computers of all time. It is anyone’s guess that with the continuing innovation coming out of the Raspberry Pi Foundation and the thousands of people across the planet constantly demonstrating newer and better examples innovative solutions with the various flavors of Raspberry Pi, what new heights this product line might reach!

One of the main goals of the Raspberry Pi is affordability. And the purpose of this book is to allow the beginner to learn Programming in Python, as well as manipulating hardware. The reader may have worked a little bit on hardware, and a little bit on programming, and want to strengthen skills in either area. The reader may also just be interested in doing more projects with the Pi Zero in Python, and of course, some of the projects in this book, briefly highlighted below might be of interest.

The book starts off with some warm up examples, helping develop a familiarity with the Raspberry Pi environment, and the projects increase in variety and complexity as the book progresses. While, readers who have advanced a bit before approaching the book can skip a few chapters, we recommend beginners progress through all chapters, since the concepts build on top of each other.

What this book covers

Chapter 1, Getting Started with Python and the Raspberry Pi Zero, introduces the Raspberry Pi Zero and the Python programming language, its history, and its features. We will set up the Raspberry Pi for Python development and write the