Book Image

Practical Python Programming for IoT

By : Gary Smart

Book Image

Practical Python Programming for IoT

By: Gary Smart

Overview of this book

The age of connected devices is here, be it fitness bands or smart homes. It's now more important than ever to understand how hardware components interact with the internet to collect and analyze user data. The Internet of Things (IoT), combined with the popular open source language Python, can be used to build powerful and intelligent IoT systems with intuitive interfaces. This book consists of three parts, with the first focusing on the "Internet" component of IoT. You'll get to grips with end-to-end IoT app development to control an LED over the internet, before learning how to build RESTful APIs, WebSocket APIs, and MQTT services in Python. The second part delves into the fundamentals behind electronics and GPIO interfacing. As you progress to the last part, you'll focus on the "Things" aspect of IoT, where you will learn how to connect and control a range of electronic sensors and actuators using Python. You'll also explore a variety of topics, such as motor control, ultrasonic sensors, and temperature measurement. Finally, you'll get up to speed with advanced IoT programming techniques in Python, integrate with IoT visualization and automation platforms, and build a comprehensive IoT project. By the end of this book, you'll be well-versed with IoT development and have the knowledge you need to build sophisticated IoT systems using Python.

Preface

Who this book is for

What this book covers

To get the most out of this book

Download the example code files

Download the color images

Conventions used

Section 1: Programming with Python and the Raspberry Pi

Section 1: Programming with Python and the Raspberry Pi

Free Chapter

Setting Up your Development Environment

Setting Up your Development Environment

Technical requirements

Understanding your Python installation

Setting up a Python virtual environment

Installing Python GPIO packages with pip

Anatomy of a virtual environment

Alternative methods of executing a Python script

Using sudo within virtual environments

Executing Python scripts outside of their virtual environments

Running a Python script at boot

Configuring the GPIO interface on our Raspberry Pi

Configuring the PiGPIO daemon

Further reading

Getting Started with Python and IoT

Getting Started with Python and IoT

Technical requirements

Creating a breadboard prototype circuit

Understanding the breadboard

Positioning and connecting the push button

Positioning and connecting the LED

Positioning and connecting the resistor

Reading an electronic schematic diagram

Reading the push button schematic connection

Reading the LED and resistor schematic connection

Introducing ground connections and symbols

Exploring two ways to flash an LED in Python

Blinking with GPIOZero

Pin Factory configuration

Blinking the LED

Blinking with PiGPIO

PiGPIO and pin configuration

Blinking the LED

Comparing the GPIOZero and PiGPIO examples

Exploring two ways to integrate a push button in Python

Responding to a button press with GPIOZero

Button pressed handler

Button configuration

Preventing the main thread from terminating

Responding to a button press with PiGPIO

Button pin configuration

Button pressed handler

Creating your first IoT program

Running and testing the Python server

Understanding the server code

Variable definitions

The resolve_thing_name() method

The get_lastest_dweet() method

The poll_dweets_forever() method

The process_dweet() method

The main program entry point

Extending your IoT program

Implementing a dweeting button

PiGPIO LED as a class

Further reading

Networking with RESTful APIs and Web Sockets Using Flask

Networking with RESTful APIs and Web Sockets Using Flask

Technical requirements

Introducing the Flask microservices framework

Creating a RESTful API service with Flask-RESTful

Running and testing the Python server

Understanding the server code

Flask and Flask-RESTful API instance variables

Global variables

The init_led() method

Serving a web page

The LEDControl class

The get() class method

The post() class method

LEDController registration and starting the server

Introduction to PWM

Adding a RESTful API client web page

Understanding the client-side code

JavaScript imports

The getState() function

The postUpdate() function

The updateControls() function

Registering event handlers with jQuery

The web page HTML

Creating a Web Socket service with Flask-SocketIO

Running and testing the Python server

Server code walkthrough

Flask and Flask-RESTful API instance variables

Serving a web page

Connecting and disconnecting handlers

Starting the server

Adding a Web Socket client web page

Understanding the client-side code

Socket.IO connect and disconnect handlers

The on LED handler

The document ready function

The web page HTML

Comparing the RESTful API and Web Socket servers

Further reading

Networking with MQTT, Python, and the Mosquitto MQTT Broker

Networking with MQTT, Python, and the Mosquitto MQTT Broker

Technical requirements

Installing the Mosquitto MQTT broker

Learning MQTT by example

Publishing and subscribing MQTT messages

Exploring MQTT topics and wildcards

Applying Quality of Service to messages

Retaining messages for later delivery

Publishing a retained message

Creating durable connections

Saying goodbye with a Will

Using MQTT broker services

Introducing the Python Paho-MQTT client library

Controlling an LED with Python and MQTT

Running the LED MQTT example

Understanding the code

Global variables

The set_led_level(data) method

The on_connect() and on_disconnect() MQTT callback methods

The on_message() MQTT callback method

The init_mqtt() method

Main entry point

Building a web-based MQTT client

Understanding the code

Global variables

The Paho JavaScript MQTT client

Connecting to the broker

The onConnectionLost and onMessageArrived handler methods

JQuery document ready function

Further reading

Section 2: Practical Electronics for Interacting with the Physical World

Section 2: Practical Electronics for Interacting with the Physical World

Connecting Your Raspberry Pi to the Physical World

Connecting Your Raspberry Pi to the Physical World

Technical requirements

Understanding Raspberry Pi pin numbering

Exploring popular Python GPIO libraries

Reviewing GPIOZero – simple interfacing for beginners

Reviewing RPi.GPIO – a low-level GPIO for beginners

Reviewing Circuit Python and Blinka – interfacing for complex devices

Reviewing PiGPIO – a low-level GPIO library

Exploring remote GPIO with PiGPIO (and GPIOZero)

Reviewing SPIDev and SMBus – dedicated SPI and I2C libraries

Exploring Raspberry Pi electronic interfacing options

Understanding digital IO

Understanding analog IO

Understanding Pulse-Width Modulation

Creating PWM signals

Understanding SPI, I2C, and 1-wire interfaces

Understanding the serial / UART protocol

Interfacing with an analog-to-digital converter

Building the ADS1115 ADC circuit

Making sure the ADS1115 is connected to your Raspberry Pi

Reading analog input with the ADS1115

Understanding the code

ADS1115 setup and configuration

Global variables

Program entry point

Using PWM to control an LED

Understanding the code

Global variables

Range mapping function

Generating the PWM signal

Visually exploring PWM with PiScope

Visualizing software and hardware-timed PWM

Further reading

Electronics 101 for the Software Engineer

Electronics 101 for the Software Engineer

Technical requirements

Fitting out your workshop

Buying electronic modules and components

Purchasing lose components

Purchasing open source hardware modules

Keeping your Raspberry Pi safe

Three ways electronic components fail

Electronics interfacing principles for GPIO control

Ohm's Law and power

Kirchhoff's circuit laws

Why are we using a 200 Ohm resistor for the LED circuit?

Calculating the resistor value

Factoring in the Raspberry Pi's current limits

Calculating the resistor's power dissipation

Exploring digital electronics

Using pull-up and pull-down resistors

The resistor solution

The code solution

Exploring analog electronics

Voltage dividers

Understanding logic-level conversion

Voltage dividers as logic-level converters

Logic-level converter ICs and modules

Comparing voltage dividers and logic-level converters

Further reading

Section 3: IoT Playground - Practical Examples to Interact with the Physical World

Section 3: IoT Playground - Practical Examples to Interact with the Physical World

Turning Things On and Off

Turning Things On and Off

Technical requirements

Exploring a relay driver circuit

Determining a load's voltage and current

Measuring the current requirement of a DC motor

Measuring the current requirement of a relay and LED

Using an optocoupler as a switch

Building the optocoupler circuit

Controlling the optocoupler with Python

Using a transistor as a switch

Building the MOSFET circuit

Controlling the MOSFET with Python

Using a relay as a switch

Building the relay driver circuit

Controlling the Relay Driver Circuit with Python

Further reading

Lights, Indicators, and Displaying Information

Lights, Indicators, and Displaying Information

Technical requirements

Making color with an RGB LED and PWM

Creating the RGB LED circuit

Running and exploring the RGB LED code

Controlling a multi-color APA102 LED strip with SPI

Creating the APA102 circuit

Powering the APA102 circuit

Configuring and running the APA102 LED strip code

APA102 LED strip code walkthrough

Discussion of APA102 and the SPI interface

APA102 LED strip troubleshooting tips

Using an OLED display

Connecting the OLED display

Verifying whether the OLED display is connected

Configuring and running the OLED example

OLED code walkthrough

Making sound with buzzers and PWM

Building the RTTTL circuit

Running the RTTTL music example

Further reading

Measuring Temperature, Humidity, and Light Levels

Measuring Temperature, Humidity, and Light Levels

Technical requirements

Measuring temperature and humidity

Creating the DHT11/DHT22 circuit

Running and exploring the DHT11/DHT22 code

Detecting light

Creating an LDR light-detecting circuit

Running the LDR example code

LDR code walkthrough

LDR configuration summary

Detecting moisture

Comparing detection options

Movement with Servos, Motors, and Steppers

Movement with Servos, Motors, and Steppers

Technical requirements

Using PWM to rotate a servo

Connecting a servo to your Raspberry Pi

How a servo is controlled using PWM

Running and exploring the servo code

Different types of servos

Using an H-Bridge IC to control a motor

Building the motor driver circuit

Running the example H-Bridge code to control a motor

Introduction to stepper motor control

Connecting the stepper motor to the L293D circuit

Running and exploring the stepper motor code

Measuring Distance and Detecting Movement

Measuring Distance and Detecting Movement

Technical requirements

Detecting movement with a PIR sensor

Creating the PIR sensor circuit

Running and exploring the PIR sensor code

Measuring distance with an ultrasonic sensor

How an ultrasonic distance sensor works

HC-SR04 distance measurement process

Building the HC-SR04 circuit

Running and exploring the HC-SR04 example code

Detecting movement and distance with Hall-effect sensors

Creating a Hall-effect sensor circuit

Running and exploring the Hall-effect sensor code

Advanced IoT Programming Concepts - Threads, AsyncIO, and Event Loops

Advanced IoT Programming Concepts - Threads, AsyncIO, and Event Loops

Technical requirements

Building and testing our circuit

Building the reference circuit

Running the examples

Exploring the event-loop approach

Exploring a threaded approach

Exploring the publisher-subscriber alternative

Exploring an AsyncIO approach

An asynchronous experiment

Further reading

IoT Visualization and Automation Platforms

IoT Visualization and Automation Platforms

Technical requirements

Triggering an IFTTT Applet from your Raspberry Pi

Creating the temperature monitoring circuit

Creating and configuring an IFTTT Applet

Triggering an IFTTT Webhook

Triggering an IFTTT Applet in Python

Actioning your Raspberry Pi from an IFTTT Applet

Method 1 – using the dweet.io service as an intermediary

Method 2 – creating a Flask-RESTful service

Creating the LED circuit

Running the IFTTT and LED Python program

Creating the IFTTT Applet

Controlling the LED from an email

IFTTT troubleshooting

Visualizing data with the ThingSpeak platform

Configuring the ThinkSpeak platform

Configuring and running the ThinkSpeak Python program

Other IoT and automation platforms for further exploration

ThingsBoard IoT platform

Amazon Web Services (AWS)

Microsoft Azure, IBM Watson, and Google Cloud

Tying It All Together - An IoT Christmas Tree

Tying It All Together - An IoT Christmas Tree

Technical requirements

Overview of the IoT Christmas tree

Building the IoTree circuit

Three IoTree service programs

Configuring, running, and using the Tree API service

Configuring the Tree API service

Running the Tree API service

Configuring, running, and using the Tree MQTT service

Configuring the Tree MQTT service

Running the Tree MQTT service program

Integrating the IoTree with dweet.io

Configuring the Tree MQTT service

Running the dweet integration service program

Integrating with email and Google Assistant via IFTTT

Integration with email

Integration with Google Assistant

Ideas and suggestions to extend your IoTree

Assessments

Other Books You May Enjoy

Other Books You May Enjoy

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Chapter 8

Check that your power supply can deliver enough current (and voltage) to your LED strip. Current requirements increase in proportion with the number of LEDs you want to illuminate, and the color and brightness they are set to. An insufficient current can mean that the internal red/green/blue LEDs are not illuminated correctly and thus the colors are not as you expected.
The absence of a Slave Select or Client Enable pin means that the APA102 takes full control of the SPI interface. This means that you cannot connect more than one SPI slave to an SPI pin (unless you employ additional electronics).
First, check that your logic level converter is connected correctly. Secondly, it's possible that the logic level converter cannot convert logic levels fast enough to keep up with the SPI interface. Try lowering the SPI bus speed.
We use the PIL (Python Imaging Library) to create an in-memory image representing what we want to display. We then send this image to the OLED display...