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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
MicroPython is an open source implementation of Python 3 that runs in embedded environments. With MicroPython, you can write clean and simple Python code to control hardware instead of using complex low-level languages such as C and C++. This book guides you through all the major applications of the MicroPython platform to build and program projects that use microcontrollers.
This MicroPython book covers recipes that will help you experiment with the programming environment and hardware programmed in MicroPython. You'll find tips and techniques for building a variety of objects and prototypes that can sense and respond to touch, sound, position, heat, and light. This book will take you through the uses of MicroPython with a variety of popular input devices and sensors. You'll learn techniques to handle time delays and sensor readings, and apply advanced coding techniques to create complex projects. As you advance, you'll deal with Internet of Things (IoT) devices and integration with other online web services. In addition to this, you'll use MicroPython to make music with bananas and create portable multiplayer video games that incorporate sound and light animations into the gameplay.
By the end of this book, you'll have mastered the tips and tricks to troubleshoot your development problems and take your MicroPython project to the next level.
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Seitenzahl: 435
Veröffentlichungsjahr: 2019
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MicroPython Cookbook
Copyright © 2019 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 author, nor Packt Publishing or its dealers and distributors, will be held liable for any damages caused or alleged to have been 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.
Commissioning Editor: Richa TripathiAcquisition Editor: Chaitanya NairContent Development Editor: Ruvika RaoTechnical Editor: Romy DiasCopy Editor:Safis EditingProject Coordinator:Vaidehi SawantProofreader: Safis EditingIndexer:Darshana JainGraphics: Alishon MendonsaProduction Coordinator: Alishon Mendonsa
First published: May 2019
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ISBN 978-1-83864-995-1
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Contributors
About the author
Marwan Alsabbagh has been coding in some form or other since before the web existed and has continued to develop software, with a particular passion for Python, his preferred programming language, for over a decade. He has been a speaker at a number of global Python conferences, where he has been known to present microcontroller projects with a healthy dose of humor and stage theatrics. The snow globe intruder alert system, which he created with his creative and curious daughters, was one of his favorite MicroPython projects. His research interests include software engineering, microcontrollers, and 3D printing.
About the reviewers
Arunkumar NT is 43 years of age, has completed his M.Sc. (Phy) and MBA (Finance), and is currently pursuing his CMA and CS qualifications. He has over 20 years' corporate experience and 2 years' experience of teaching MBA students. He is an entrepreneur and has previously worked for Airtel, Citi Finance, and ICICI Bank. He has also worked on the Python for Finance book.
Bhaumik Vaidya is an experienced computer vision engineer and mentor. He has worked extensively on OpenCV and the TensorFlow library to solve computer vision problems. He is a University gold medalist at the master's level, and is now doing his PhD on the acceleration of computer vision algorithms built using OpenCV and deep learning libraries, such as TensorFlow and Keras, on GPUs. He, along with his PhD mentor, has also received an NVIDIA Jetson TX1, which is an embedded development platform, as a research grant from NVIDIA. He has previously worked in the VLSI domain as an ASIC verification engineer. He has published numerous research papers in reputable journals, has filed two provisional patents, and has written one book on computer vision and GPU programming.
Packt is searching for authors like you
If you're interested in becoming an author for Packt, please visit authors.packtpub.com and apply today. We have worked with thousands of developers and tech professionals, just like you, to help them share their insight with the global tech community. You can make a general application, apply for a specific hot topic that we are recruiting an author for, or submit your own idea.
Table of Contents
Title Page
Copyright and Credits
MicroPython Cookbook
About Packt
Why subscribe?
Packt.com
Contributors
About the author
About the reviewers
Packt is searching for authors like you
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
Sections
Getting ready
How to do it...
How it works...
There's more...
See also
Get in touch
Reviews
Getting started with MicroPython
What is MicroPython?
What is a microcontroller?
What is CircuitPython?
What is the Circuit Playground Express?
Where to buy
References
Flashing the microcontroller firmware
Getting ready
How to do it...
How it works...
There's more...
See also
Executing your first program
Getting ready
How to do it...
How it works...
There's more...
See also
Using screen to access the REPL
Getting ready
How to do it...
How it works...
There's more...
See also
Using Mu to access the REPL
Getting ready
How to do it...
How it works...
There's more...
See also
Executing commands in the REPL
Getting ready
How to do it...
How it works...
There's more...
See also
Using the auto-reload feature
Getting ready
How to do it...
How it works...
There's more...
See also
Updating the CircuitPython Library
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling LEDs
The Adafruit Circuit Playground Express layout
Turning on the pin 13 LED
Getting ready
How to do it...
How it works...
There's more...
See also
Setting the brightness of the NeoPixel
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling the color of a single NeoPixel
Getting ready
How to do it...
How it works...
There's more...
See also
Displaying an LED color using the RGB and hex code
Getting ready
How to do it...
How it works...
There's more...
See also
Setting an LED color using color names
Getting ready
How to do it...
How it works...
There's more...
See also
Setting all NeoPixels to the same color
Getting ready
How to do it...
How it works...
There's more...
See also
Setting a range of NeoPixels to one color
Getting ready
How to do it...
How it works...
There's more...
See also
Generating random NeoPixel LED colors
Getting ready
How to do it...
How it works...
There's more...
See also
Creating LED animations with random colors
Getting ready
How to do it...
How it works...
There's more...
See also
Creating LED animations with rainbow colors
Getting ready
How to do it...
How it works...
There's more...
See also
Creating Sound and Music
The Adafruit Circuit Playground Express layout
Making a beeping sound
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling tone, frequency, and duration
Getting ready
How to do it...
How it works...
There's more...
See also
Playing a musical note
Getting ready
How to do it...
How it works...
There's more...
See also
Playing a melody
Getting ready
How to do it...
How it works...
There's more...
See also
Sounding the alarm
Getting ready
How to do it...
How it works...
There's more...
See also
Playing WAV files
Getting ready
How to do it...
How it works...
There's more...
See also
Converting MP3 files to WAV files
Getting ready
How to do it...
How it works...
There's more...
See also
Starting and stopping tones
Getting ready
How to do it...
How it works...
There's more...
See also
Interacting with Buttons
The Adafruit Circuit Playground Express layout
Detecting push button presses
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling LEDs with push buttons
Getting ready
How to do it...
How it works...
There's more...
See also
Reading a slide switch
Getting ready
How to do it...
How it works...
There's more...
See also
Calling functions on the button state change
Getting ready
How to do it...
How it works...
There's more...
See also
Moving active LEDs with push buttons
Getting ready
How to do it...
How it works...
There's more...
See also
Playing a beep on the button press
Getting ready
How to do it...
How it works...
There's more...
See also
Detecting touch on a touchpad
Getting ready
How to do it...
How it works...
There's more...
See also
Monitoring the touchpad raw measurements
Getting ready
How to do it...
How it works...
There's more...
See also
Adjusting the touch threshold
Getting ready
How to do it...
How it works...
There's more...
See also
Reading Sensor Data
Circuit Playground Express sensors
Reading temperature readings
Getting ready
How to do it...
How it works...
There's more...
See also
Reading brightness levels from the light sensor
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a light meter
Getting ready
How to do it...
How it works...
There's more...
See also
Reading data from the motion sensor
Getting ready
How to do it...
How it works...
There's more...
See also
Detecting a single or double tap
Getting ready
How to do it...
How it works...
There's more...
See also
Detecting a shake
Getting ready
How to do it...
How it works...
There's more...
See also
Beeping on a shake
Getting ready
How to do it...
How it works...
There's more...
See also
Button Bash Game
Technical requirements
Circuit Playground Express power
Creating a class to detect a button state change
Getting ready
How to do it...
How it works...
There's more...
See also
Creating your own Python modules
Getting ready
How to do it...
How it works...
There's more...
See also
Adding button interactions to the event loop
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a generator to get pixel colors
Getting ready
How to do it...
How it works...
There's more...
See also
Showing scores with the ScoreBoard class
Getting ready
How to do it...
How it works...
There's more...
See also
Detecting winners with the ScoreBoard class
Getting ready
How to do it...
How it works...
There's more...
See also
Adding the ScoreBoard class to the event loop
Getting ready
How to do it...
How it works...
There's more...
See also
Fruity Tunes
Technical requirements
Circuit Playground Express touchpads
Creating a class to react to touch events
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to enable speaker output
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to play audio files
Getting ready
How to do it...
How it works...
There's more...
See also
Using the NeoPixel object to control pixels
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a touch handler to play sounds
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a touch handler to light up pixels
Getting ready
How to do it...
How it works...
There's more...
See also
Creating an event loop to handle all touch events
Getting ready
How to do it...
How it works...
There's more...
See also
Let's Move It, Move It
Technical requirements
DC motors
Servos
Adafruit CRICKIT
Where to buy
Tuning a servo to the correct pulse width
Getting ready
How to do it...
How it works...
There's more...
See also
Setting the actuation range of a servo
Getting ready
How to do it...
How it works...
There's more...
See also
Setting the angle of a servo
Getting ready
How to do it...
How it works...
There's more...
See also
Sweeping a servo
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling servos with buttons
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling multiple servos
Getting ready
How to do it...
How it works...
There's more...
See also
Turning on a DC motor
Getting ready
How to do it...
How it works...
There's more...
See also
Setting the speed and direction of a DC motor
Getting ready
How to do it....
How it works...
There's more...
See also
Controlling a DC motor with buttons
Getting ready
How to do it...
How it works...
There's more...
See also
Coding on the micro:bit
Technical requirements
The micro:bit
Using Mu to flash code onto the micro:bit
Getting ready
How to do it...
How it works...
There's more...
See also
Using Mu to get a REPL on the micro:bit
Getting ready
How to do it...
How it works...
There's more...
See also
Displaying a single character on the LED display
Getting ready
How to do it...
How it works...
There's more...
See also
Displaying a built-in image
Getting ready
How to do it...
How it works...
There's more...
See also
Displaying scrolling text
Getting ready
How to do it...
How it works...
There's more...
See also
Showing which button has been pressed
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a countdown timer
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling the ESP8266
Technical requirements
The Adafruit Feather HUZZAH ESP8266
Where can you buy these?
Using the REPL over a serial connection
Getting ready
How to do it...
How it works...
There's more...
See also
Scanning for available Wi-Fi networks
Getting ready
How to do it...
How it works...
There's more...
See also
Configuring settings for AP mode
Getting ready
How to do it...
How it works...
There's more...
See also
Connecting to an existing Wi-Fi network
Getting ready
How to do it...
How it works...
There's more...
See also
Using the WebREPL over Wi-Fi
Getting ready
How to do it...
How it works...
There's more...
See also
Transferring files with the WebREPL CLI
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling the blue and red LEDs
Getting ready
How to do it...
How it works...
There's more...
See also
Interacting with the Filesystem
Technical requirements
Remounting the filesystem
Getting ready
How to do it...
How it works...
There's more...
See also
Listing files
Getting ready
How to do it...
How it works...
There's more...
See also
Removing files
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a directory
Getting ready
How to do it...
How it works...
There's more...
See also
Reading a file's contents
Getting ready
How to do it...
How it works...
There's more...
See also
Writing a file's contents
Getting ready
How to do it...
How it works...
There's more...
See also
Calculating disk usage
Getting ready
How to do it...
How it works...
There's more...
See also
Networking
Technical requirements
Performing a DNS lookup
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to wait for internet connectivity
Getting ready
How to do it...
How it works...
There's more...
See also
Performing an HTTP request using raw sockets
Getting ready
How to do it...
How it works...
There's more...
See also
Performing an HTTP request using the urequests library
Getting ready
How to do it...
How it works...
There's more...
See also
Fetching JSON data from a RESTful web service
Getting ready
How to do it...
How it works...
There's more...
See also
Creating an HTTP server
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a web handler module
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling LEDs through the web server
Getting ready
How to do it...
How it works...
There's more...
See also
Developing a RESTful API to control the LEDs
Getting ready
How to do it...
How it works...
There's more...
See also
Interacting with the Adafruit FeatherWing OLED
The Adafruit FeatherWing OLED
Where to buy it
Technical requirements
Detecting button presses with GPIO pins
Getting ready
How to do it...
How it works...
There's more...
See also
Connecting to the SSD1306 display
Getting ready
How to do it...
How it works...
There's more...
See also
Filling and clearing the display
Getting ready
How to do it...
How it works...
There's more...
See also
Setting pixels on the display
Getting ready
How to do it...
How it works...
There's more...
See also
Drawing lines and rectangles on the display
Getting ready
How to do it...
How it works...
There's more...
See also
Writing text on the display
Getting ready
How to do it...
How it works...
There's more...
See also
Inverting colors on the display
Getting ready
How to do it...
How it works...
There's more...
See also
Building an Internet of Things (IoT) Weather Machine
Technical requirements
Retrieving weather data from the internet
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to get a city's weather
Getting ready
How to do it...
How it works...
There's more...
See also
Randomly selecting cities
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a Screen object for text handling
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to show a city's weather
Getting ready
How to do it...
How it works...
There's more...
See also
Providing visual feedback when fetching data
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a function to display the weather for a random city
Getting ready
How to do it...
How it works...
There's more...
See also
Creating an IoT button to show the weather around the world
Getting ready
How to do it...
How it works...
There's more...
See also
Coding on the Adafruit HalloWing Microcontroller
The Adafruit HalloWing M0 Express
Where to buy
Technical requirements
Discovering I2C devices
Getting ready
How to do it...
How it works...
There's more...
See also
Reading data from the accelerometer using I2C
Getting ready
How to do it...
How it works...
There's more...
See also
Detecting board-flipping with the accelerometer
Getting ready
How to do it...
How it works...
There's more...
See also
Controlling screen brightness
Getting ready
How to do it...
How it works...
There's more...
See also
Displaying a bitmap image
Getting ready
How to do it...
How it works...
There's more...
See also
Listing all image files
Getting ready
How to do it...
How it works...
There's more...
See also
Creating a joke-telling machine
Getting ready
How to do it...
How it works...
There's more...
See also
Other Books You May Enjoy
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Preface
MicroPython is a lean implementation of the Python 3 programming language that is capable of running on a wide range of microcontrollers. It provides the majority of features in the Python programming language, such as functions, classes, lists, dictionaries, strings, reading and writing files, list comprehensions, and exception handling to these microcontrollers.
Microcontrollers are tiny computers that usually include a CPU, memory, and input/output peripherals. Even though they will have more limited resources compared to a PC, they can be made to a much smaller dimension, with less power consumption and at a lower cost. These strengths make it possible to use them in a wide range of new applications that weren’t possible before.
This book will cover a number of different features in the MicroPython language, as well as a number of different microcontroller boards. The initial chapters will provide simple and easy to understand recipes to get these boards to interact with people and their environment. Topicsrangingfrom reading temperature, light, and motion data from sensors to interacting with push buttons, slide switches, and touchpads will also be covered. Producing output on these boards with audio playback and LED animations will also be covered in the early chapters. Once this foundation is in place, we will build more involved projects, such as interactive two-player games, electronic musical instruments, and an Internet of Things (IoT) weather machine. You will be able to take the skills you learn from these recipes and directly apply them to your own embedded projects.
Who this book is for
This book aims to help people apply the power and ease of use of the Python language to the versatility of microcontrollers. Prior knowledge of Python is expected in order to understand this book.
What this book covers
Chapter 1, Getting Started with MicroPython, introduces the Adafruit Circuit Playground Express microcontroller and teaches the core skills for using MicroPython on this hardware.
Chapter 2, Controlling LEDs, covers methods of controlling NeoPixel LEDs, the color of the lights, and how to create animated light shows by controlling the timing of light changes on the board.
Chapter 3, Creating Sound and Music, discusses methods of how to make sounds and playmusic on the Adafruit Circuit Playground Express. Topics such as making the board beep at a certain sound frequency and playing music files using the WAV file format and the board's built-in speakers will be covered.
Chapter 4, Interacting with Buttons, shows methods of interacting with the buttons and touch pads that come on board with the Adafruit Circuit Playground Express. The basics of detecting when a button is pressed or not, as well as advanced topics, such as fine tuning the touch threshold of the capacitive touch pads, will be discussed.
Chapter 5, Reading Sensor Data, introduces methods of reading sensor data from a number of different types of sensors, such as temperature, light, and motion sensors.
Chapter 6, Button Bash Game, guides us to create a two-player game called Button Bash that you can play directly on the Circuit Playground Express using the push buttons, NeoPixels, and built-in speakers.
Chapter 7, Fruity Tunes, explains how to create a musical instrument with the Adafruit Circuit Playground Express and some bananas. Touchpads will be used to interact with the bananas and play different musical sounds each time you touch a different banana.
Chapter 8, Let's Move It, Move It, introduces the Adafruit CRICKIT hardware add-on that will help control motors and servos through our Python scripts; in particular, their speed, rotational direction, and angle will be controlled through these scripts.
Chapter 9, Coding on the micro:bit, covers methods of interacting with the micro:bit platform. How to control its LED grid display and interact with the buttons that come on board will be discussed.
Chapter 10, Controlling the ESP8266, introduces the Adafruit Feather HUZZAH ESP8266 microcontroller, and discusses its features and strengths compared to other microcontrollers. Topics such as connecting to Wi-Fi networks, using the WebREPL, and transferring files over Wi-Fi will be covered.
Chapter 11, Interacting with the Filesystem, discusses a number of topics related to the operating system (OS), such as listing files, removing files, creating directories, and calculating disk usage.
Chapter 12, Networking, discusses how to perform a number of different network operations, such as DNS lookups, implementing an HTTP client, and HTTP servers.
Chapter 13, Interacting with the Adafruit FeatherWing OLED, introduces the Adafruit FeatherWing OLED hardware add-on, which can be attached to the ESP8266 to add a display to an internet-connected microcontroller, to display display text graphics and interact with the user using the included three hardware push buttons.
Chapter 14, Building an IoT Weather Machine, explains how to create an IoT device that will retrieve weather data and show it to the user at the press of a button from the IoT device itself.
Chapter 15, Coding on the Adafruit HalloWing, introduces the Adafruit HalloWing microcontroller, which comes with a 128x128 full-color Thin-Film Transistor (TFT) display built into it, providing the ability to display rich graphical images on the microcontroller.
To get the most out of this book
Readers are expected to have a basic knowledge of the Python programming language. It would be beneficial for readers to have a basic understanding of importing packages and working with the REPL to get the most out of this book.
Download the example code files
You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.com/support and register to have the files emailed directly to you.
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The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/MicroPython-Cookbook. We also have other code bundles from our rich catalog of books and videos available athttps://github.com/PacktPublishing/. Check them out!
Download the color images
We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: https://www.packtpub.com/sites/default/files/downloads/9781838649951_ColorImages.pdf.
Sections
In this book, you will find several headings that appear frequently (Getting ready, How to do it..., How it works..., There's more..., and See also).
To give clear instructions on how to complete a recipe, use these sections as follows:
Getting ready
This section tells you what to expect in the recipe and describes how to set up any software or any preliminary settings required for the recipe.
How to do it...
This section contains the steps required to follow the recipe.
How it works...
This section usually consists of a detailed explanation of what happened in the previous section.
There's more...
This section consists of additional information about the recipe in order to make you more knowledgeable about the recipe.
See also
This section provides helpful links to other useful information for the recipe.
Get in touch
Feedback from our readers is always welcome.
General feedback: Email [email protected] and mention the book title in the subject of your message. If you have questions about any aspect of this book, please email us at [email protected].
Errata: Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you have found a mistake in this book, we would be grateful if you would report this to us. Please visit www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details.
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Getting started with MicroPython
It's an exciting time to work with technologies such as MicroPython. They make tiny and inexpensive hardware devices more accessible, as you can use a high-level language such as Python to code on them. Tasks such as retrieving data from web services can easily be done in a few lines of code, compared to other microcontroller languages that would require many more steps, because they operate at such a low level compared to Python. This is very empowering, as you will get results faster and be able to iterate through different designs and prototypes in a shorter amount of time.
In this chapter, we will provide you with the essential skills to get started and be productive with the software and hardware needed to run MicroPython. You'll learn how to update the firmware and libraries on the device. Recipes to load your first program on the board and use advanced features, such as auto-reloading your code, will also be covered. Finally, a number of recipes will cover the usage of the REPL that is a powerful way to quickly interact and experiment with the available components on MicroPython devices.
In this chapter, we will be covering the following recipes:
Flashing the microcontroller firmware
Executing your first program
Using screen to access the REPL
Using Mu to access the REPL
Executing commands in the REPL
Using the auto-reload feature
Updating the CircuitPython Library
What is MicroPython?
MicroPython is the creation of the Australian programmer and physicist Damien George, who launched a Kickstarter campaign in 2013 to support the development of the language and the initial microcontroller hardware that it would run on. After the success of the project, more and more devices (which have a variety of chipsets from different manufactures) have become supported by MicroPython, creating a wide range of devices from which to choose when you make a project using MicroPython.
MicroPython is a lean implementation of the Python 3 programming language that is capable of running on hardware with very limited resources, such as microcontrollers. MicroPython has implemented the majority of features in the Python programming language, such as functions, classes, lists, dictionaries, strings, reading and writing files, list comprehensions, and exception handling.
The REPL is also implemented and can be interacted with using a serial connection. A selection of the core Python libraries is provided, which allows a range of applications to be implemented. The JSON and socket libraries allow web client and server implementations, making Python-based Internet of Things (IoT) projects on microcontrollers a reality.
By bringing one of the most popular and easy to use programming languages to the exciting world of embedded computing, MicroPython opens up new doors for makers and entrepreneurs to bring their creations to life. This book will explore the different ways to leverage the MicroPython language with a variety of unique microcontroller devices that each bring a different set of capabilities to the table.
One of the unique and fascinating aspects of running MicroPython on microcontrollers is that it does not run on an operating system (OS), but instead runs directly on bare metal. These unique characteristics manifest themselves in many ways, such as the ability to run your Python code at the instant the hardware is powered on, as there is no OS that needs to boot up.
The other aspect of this is that the Python code has direct access to control and interact with the hardware, creating hardware possibilities that would not be possible with a typical Python application running on an OS.
As we know now that MicroPython runs on a microcontroller, let's see what microcontrollers are all about.
What is a microcontroller?
Microcontrollers are small computers on a single chip. They usually include a CPU, memory, and input/output peripherals. They will have more limited computing resources than what might be found on a modern PC.
Compared to a PC, however, they can be made to a much smaller dimension, allowing them to be embedded in all sorts of electronic and mechanical devices. Their power consumption is often far less in orders of magnitude, thus providing battery life for days. They have a much lower cost per unit, which opens up possibilities of having hundreds of such devices to collect sensor data across a broad geographical area and still be financially feasible.
Traditionally, it was a difficult process to create applications on microcontrollers because you would have to write very low-level code that took time and was difficult to debug. MicroPython brings the ease of use of Python to microcontroller. It's able to provide this easier interaction with the hardware, and yet still work in such a resource constrained environment and provide a wide range of functionality with a strong level of responsiveness.
What is CircuitPython?
CircuitPython is a branch of MicroPython created by Adafruit Industries that makes working with microcontrollers simpler. It has excellent support for many of the sensors and components that come with Adafruit devices through its Python libraries. It also allows code to be easily loaded and run without having to install any additional software applications by exposing the microcontroller's storage as a disk drive.
Generally, the differences between MicroPython and CircuitPython are minor, and, in many instances, code will run the same on both implementations.
What is the Circuit Playground Express?
The Adafruit Circuit Playground Express is an inexpensive, yet versatile microcontroller with a rich set of input and output devices that comes built-in with the device. The following are some of the main hardware features present in this device:
10 mini NeoPixels, each with the ability to display a full range of colors
As motion sensor (triple-axis accelerometer with tap detection and free-fall detection)
A temperature sensor
A light sensor
A sound sensor
A mini speaker
Two push buttons, which are labeled A and B
A slide switch
An infrared receiver and transmitter
Eight alligator-clip friendly input/output pins
Supports I2C and PWM output
Seven capacitive touch inputs
A red LED
A reset button
An ATSAMD21 ARM Cortex M0 processor, running at 3.3 V and 48 MHz
2 MB of flash storage
A micro USB port for connecting to a PC
These will be the only required devices for eight chapters. Later chapters will introduce a different set of devices.
Where to buy
The Adafruit Circuit Playground Express can be purchased directly from Adafruit (https://www.adafruit.com/product/3333). It can also be purchased from online retailers, such as Amazon and Pimoroni.
For the purpose of this book, we recommend buying the Circuit Playground Express – Base Kit (https://www.adafruit.com/product/3517) and also includes a USB cable and battery pack so that projects can easily be made portable.
References
Here are a few references:
The MicroPython web page at
http://micropython.org
The MicroPython project on Kickstarter at
https://www.kickstarter.com/projects/214379695/micro-python-python-for-microcontrollers
An article in microcontrollers on PC Mag at
https://www.pcmag.com/encyclopedia/term/46924/microcontroller
The Adafruit learning guide on CircuitPython at
https://learn.adafruit.com/welcome-to-circuitpython/what-is-circuitpython
The CircuitPython official documentation at
https://circuitpython.readthedocs.io
Flashing the microcontroller firmware
In this recipe, we will show how to flash the firmware on the Circuit Playground Express with the latest CircuitPython firmware. There are two reasons to this before you start working with this device. First, the device also supports the Microsoft MakeCode programming environment and flashing the device with the CircuitPython firmware prepares it for use with the Python language.
Second, the CircuitPython language is under constant development, with a release every few months, so it is a good idea to update the firmware from time to time to load the latest release of the language onto the board.
Getting ready
This chapter's introduction gives us directions on how to buy the Circuit Playground Express,which will be required for all the recipes in this chapter.A USB micro B cable and a computer running macOS, Windows, or Linuxwillalsobe required.
How to do it...
Let's look at the following steps:
Download the latest CircuitPython Circuit Playground Express UF2 file (
https://github.com/adafruit/circuitpython/releases/latest
). The name of the UF2 file for version 3.1.2 of CircuitPython is
adafruit-circuitpython-circuitplayground_express-3.1.2.uf2
. For each release of CircuitPython, there are many different
uf2
files for different supported microcontrollers. Make sure that you download the file for the Circuit Playground Express device.
Connect the USB cable to the Circuit Playground Express and the computer.
Double-click the reset button located at the center of the board. If all goes well, you will see all the LEDs turn green; otherwise, there is most likely an issue with the USB cable being used. In some instances, if a double-click doesn't work, try a single click of the reset button.
You will see a new disk appear called
CPLAYBOOT
:
Copy the UF2 file into this drive.
Once the UF2 file has been fully written to the device, the firmware will be updated and a new drive will appear, called
CIRCUITPY
:
Now, our Circuit Playground Express can be used.
How it works...
Traditionally, special software has had to be installed and used to handle the delicate process of flashing a microcontroller. Microsoft developed the UF2 method, which greatly simplifies the process by not requiring any special software or command-line execution to flash the microcontroller.
Once the board is placed into the bootloader mode, it will then expect a UF2 file to be saved to it. When the UF2 is copied to the drive, the microcontroller will detect that the file copy has been completed and then automatically proceed to flash the microcontroller and restart the device, at which point the device is reattached and ready to be used.
There's more...
The UF2 approach to flashing microcontroller firmware makes the process easier and faster compared to previous approaches. Not all MicroPython boards support the UF2 method and so require the more involved approach of installing special software to do the firmware flashing. The exact process and software required varies between different boards and manufactures.
When you use this flashing software, it will frequently require that you know the exact name of the serial device that the device appears as on your computer. The naming of these devices varies between Windows, Linux, and macOS. This type of software is usually required to be run in the Terminal, so you'll have to have some command-line knowledge to inter with it. For all these reasons, the use of UF2 with supported devices such as the Circuit Playground Express is the preferred way of starting your experimentation with MicroPython.
See also
There are a number of resources, both on the Adafruit and Microsoft websites, relating to the process described in this recipe. Here are a few references:
Documentation of updating CircuitPython can be found at
https://learn.adafruit.com/adafruit-circuit-playground-express/circuitpython-quickstart
.
The UF2 process is explained in more detail at
https://makecode.com/blog/one-chip-to-flash-them-all
.
Executing your first program
In this recipe, we will show you how to load your first program on the Circuit Playground Express and how to modify the program and reload it. The program will then light one of the ten NeoPixels that come available on the board.
Getting ready
Once theCircuit Playground Expresshas had theCircuitPythonfirmware flashed, you may load Python scripts onto the board and run them.
How it works...
When the device is turned on it looks for certain files, such as code.py ormain.py, that, if found, will be executed as part of the startup process. In this way, you can specify the code you want run when the device is powered on. The script first imports the adafruit_circuitplayground.express library so that it can control theNeoPixels.The firstNeoPixelis set to the color red by giving ita set of appropriate RGBvalues.
Finally, the script will sleep for 60 seconds so that the LED remains lit for one minute before the script ends execution.
There's more...
Now that the board has been loaded with a Python script, it can be disconnected from the computer and have the battery pack attached to it.Once the battery pack is powered on by the script, it should run and light up the selectedNeoPixel.
This is a simple way to create portable and inexpensive projects that can have a code running directly from the board with noneed for aconnected PC and canbepoweredsimplybythree AAA batteries.
See also
There are a number of files that CircuitPython looks for when it boots up, which are described at https://learn.adafruit.com/welcome-to-circuitpython?view=all#naming-your-program-file-7-30.
Using screen to access the REPL
Linux and macOS have powerful Terminal emulators, such as screen, that can be used to directly connect to the device's Read-Eval-Print Loop (REPL) over a serial (USB) connection. This recipe will show how to connect to the REPL and start running a Python code interactively.
Getting ready
EithermacOSor aLinuxcomputer may be used for this recipeand may require the screen command tobe available.On macOS, theScreen applicationis built-in and so requires no installation. On Ubuntu, the Linux Screen can be installed with theapt install screencommand.
How to do it...
Let's have a look at how to connect the REPL and run the code:
Open the computer's Terminal application.
List device names before plugging in device by running
ls /dev/ttyACM*
on Linux or
ls /dev/tty.*
on macOS.
Connect the board to your computer with a USB cable.
List the device names again with the same command to discover the device name of the board.
If the device name is
/dev/ttyACM0
, then the
screen
command would be
screen /dev/ttyACM0 115200
.
Enter the command in the Terminal and start the Screen application.
I
f Screen is able to connect successfully, the Python REPL should appear on the Terminal with output similar to the following text:
Adafruit CircuitPython 3.1.2 on 2019-01-07; Adafruit CircuitPlayground Express with samd21g18
>>>
If the prompt doesn't appear, you can try pressing
Ctrl
+
C
and then press
Enter
, which will stop the currently running Python script and run the REPL with the following message:
Press any key to enter the REPL. Use CTRL-D to reload.
Once the REPL prompt appears, we will have to test if the prompt is working by evaluating the
1+1
expression.
It should produce the following output:
>>> 1+1
2
How it works...
The Circuit Playground Express exposes a serial deviceover the USB connection,which can be accessed by a number of different Terminal emulator programs.Besidesscreen, there are other programs, such as picocom and minicom, that may also be used.
The last parameter that was set as 115,200 in the command sets the baud rate of the connection, which should be set at that speed.Once the connection is successfully established, an interactive session is commenced that allows expressions to be directly evaluated on the device and the output is directly displayed on the Terminal.
There's more...
Many of the recipes in the book will introduce the different parts of a script using the REPL. This will give you a chance to get immediate feedback as you run each snippet of code. Once you've entered the different snippets in the REPL you can also use REPL features to assist in your experimentation with the code. You can use the up and down arrow keys to move through the history of commands that have been entered in the REPL. For example, if you had just executed a line of code in the REPL that turned on a specific pixel on the board, you could press the up key and change which pixel is lit up by editing the line and pressing Enter again.
See also
Here are a few references:
The use of the REPL on CircuitPython boards is discussed in detail at
https://learn.adafruit.com/welcome-to-circuitpython/the-repl
.
Details on using the REPL to access MicroPython can be found at
https://learn.adafruit.com/micropython-basics-how-to-load-micropython-on-a-board/serial-terminal
.
