Robotics at Home with Raspberry Pi Pico: Build autonomous robots with the versatile low-cost Raspberry Pi Pico controller and Python

BIRMINGHAM—MUMBAI

Robotics at Home with Raspberry Pi Pico

Copyright © 2023 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.

Group Product Manager: Rahul Nair

Publishing Product Manager: Rahul Nair

Content Development Editor: Sujata Tripathi

Technical Editor: Rajat Sharma

Copy Editor: Safis Editing

Project Coordinator: Sean Lobo

Proofreader: Safis Editing

Indexer: Pratik Shirodkar

Production Designer: Nilesh Mohite

Senior Marketing Coordinator: Nimisha Dua

Marketing Coordinator: Gaurav Christian

First published: March 2023

Production reference: 1170223

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham

B3 2PB, UK.

ISBN 978-1-80324-607-9

www.packtpub.com

To my amazing wife, Carol, who has supported all my robotics experiments with love, inspiration, and tolerance of a living room filled with robots. To my children, Helena and Jonathan, for all their ideas and enthusiasm and for encouraging me to take a break and play with them sometimes!

– Danny Staple

Contributors

About the author

Danny Staple is a robot builder and programmer. He has been a professional software engineer since 2000, uses Python professionally, and regularly contributes to open source projects.

Danny has been building robots at home since 2004 and has a cupboard full of projects, including robots with wheels, cameras, tank tracks, legs, and arms, made from plastic, cardboard, metal, kits, lunchboxes, and modified toys.

Danny authored Learn Robotics Programming, published in 2021 by Packt Publishing, and has written magazine articles for The MagPi. He runs the robotics YouTube channel Orionrobots and brings his robots to events such as Pi Wars and Arduino Day. Danny also mentors at CoderDojo KU, where he shows kids how to program in Python and has run Lego robotics clubs.

I would like to thank the Pi Wars and Adafruit communities for answering my tricky questions, Mike Moncrieffe for checking diagrams for me, and my review team for the great feedback throughout this book.

About the reviewer

Leo White is a professional software engineer and a graduate of the University of Kent. His interests include electronics, 3D printing, and robotics. He first started programming on the Commodore 64 and later wrote several applications for the Acorn Archimedes. He currently programs set-top boxes for his day job. Utilizing the Raspberry Pi as a foundation, he has mechanized children’s toys and driven robot arms, blogging about his experiences and processes along the way. He has given presentations at Raspberry Jams and entered a variety of robots in the Pi Wars competition.

Table of Contents

Preface

Part 1: The Basics – Preparing for Robotics with Raspberry Pi Pico

1

Planning a Robot with Raspberry Pi Pico

Technical requirements

What is Raspberry Pi Pico, and why is it suitable for robotics?

A microcontroller that runs Python

Raspberry Pi Pico’s interfaces for sensors and devices

What is CircuitPython?

Planning a Raspberry Pi Pico robot

An overview of robot planning

A note on trade-offs

Choosing a robot chassis

Choosing the power systems

Pin usage

Test fitting a Raspberry Pi Pico robot

Creating your first test-fit part

Motors

Power systems

Creating a rough chassis

Arranging the test-fit parts

A recommended shopping list for robot basics

Robot parts and where to find them

The robot workshop and makerspaces

Summary

Exercises

Further reading

2

Preparing Raspberry Pi Pico

Technical requirements

Getting CircuitPython onto Raspberry Pi Pico

Preparing the CircuitPython library for Pico

Coding on Pico – first steps

Downloading the Mu editor

Lighting the Pico LED with CircuitPython

Blinking the LED with code

Soldering headers to Raspberry Pi Pico

Summary

Exercises

Further reading

3

Designing a Robot Chassis in FreeCAD

Technical requirements

Introducing FreeCAD

The FreeCAD screen

Selecting workbenches

FreeCAD settings

Making robot chassis sketches in FreeCAD

Preparing the document

Sketching the chassis outline

Creating the upper parts main sketch

Sketching the motor holes

Designing the caster placement

Modeling chassis parts from sketches

Modeling the chassis plate

Modeling the other parts

Troubleshooting the model

Modeling the caster in 3D

Making FreeCAD technical drawings

Setting up the page

Adding parts to the drawing

Preparing the drawing for print

Summary

Exercises

Further reading

4

Building a Robot around Pico

Technical requirements

Cutting styrene parts

Transferring CAD measurements to a plastic sheet

Cutting the plastic sheet

Finishing and sanding the chassis plate

Assembling a robot chassis

Attaching the caster and battery box

Attaching the motors and wheels

Wiring a Raspberry Pi Pico robot

Wiring Pico and the motor controller into the breadboard

Adding the batteries

Wiring in the motors and encoders

Powering the robot up

Summary

Exercises

Further reading

5

Driving Motors with Raspberry Pi Pico

Technical requirements

Driving forward and back

Testing each motor with CircuitPython

Driving wheels in a straight line

Steering with two motors

An introduction to pulse width modulation speed control

Driving fast and slow

Turning while moving

Driving along a planned path

Putting line and turn moves together

The flaw with driving this way

Summary

Exercises

Further reading

Part 2: Interfacing Raspberry Pi Pico with Simple Sensors and Outputs

6

Measuring Movement with Encoders on Raspberry Pi Pico

Technical requirements

About encoders and odometry

Absolute and relative sensing

Types of encoders

Encoder pulse data

Wiring in encoders on a Raspberry Pi Pico robot

Examining the motors

Examining the wiring

Programming Raspberry Pi Pico PIO

Introduction to PIO programming

Introducing PIOASM

Detecting input with PIO

PIO instructions and registers

Making a counter with PIO

Measuring encoder count for movement

Making a simple PIO change detection loop

Making a bidirectional counter with PIO

Making reusable encoder code

Measure counts for a known time

Summary

Exercises

Further reading

7

Planning and Shopping for More Devices

Technical requirements

Introducing sensors

Analog sensor types

Timed pulses

Data bus sensors

The robot block diagram

Choosing device types

Distance sensors

Inertial measurement unit

Bluetooth devices

Device pin usage summary

Planning what to add and where

Bluetooth and IMU mounting plan

Distance sensor mounting plan

Shopping list – parts and where to find them

Preparing the robot

Designing the shelf

Cutting the shelf

Designing the front sensor brackets

Cutting the sensor brackets

Preparing the chassis plate

Assembling the robot

Summary

Exercises

Further reading

8

Sensing Distances to Detect Objects with Pico

Technical requirements

How distance sensing works

Soldering headers and attaching them to the robot

Soldering headers

Mounting the sensors

Introduction to I2C communication

Communicating with a single distance sensor

Wiring the distance sensors

VL53LX theory of operation

Reading a single distance sensor in CircuitPython

Troubleshooting

Connecting two distance sensors

Troubleshooting

Building a wall avoider with Raspberry Pi Pico

Preparing the robot library

Wall-avoiding theory of operation

Distance sensor wall avoider code

Troubleshooting

Summary

Exercises

Additional reading

9

Teleoperating a Raspberry Pi Pico Robot with Bluetooth LE

Technical requirements

Wireless robot connection options

Connecting Bluetooth LE to Raspberry Pi Pico

Attaching the Bluetooth module to the robot

Wiring the Bluetooth breakout to Raspberry Pi Pico

Connecting to the Bluefruit LE device with UART

Connecting a smartphone

Troubleshooting the Bluefruit module

Getting sensor data over Bluetooth LE on Raspberry Pi Pico

Graphing the data

Controlling the robot with Bluetooth LE

Printing what we got

Button control mode

Decoding button control packets to drive the robot

Troubleshooting

Summary

Exercises

Further reading

Part 3: Adding More Robotic Behaviors to Raspberry Pi Pico

10

Using the PID Algorithm to Follow Walls

Technical requirements

Introducing the PID algorithm

Control and feedback

Bang-bang control

Distance sensing with proportional control

Troubleshooting

Using the integral to handle small distances

Dealing with oscillations using the derivative

Using PID to follow a wall

Changing the sensor’s placement

Wall-following code

Troubleshooting

PID tuning – using graphs to tune the PID

Controlling motor speed

The proportional component

Adjusting the derivative gain

Tuning the integral

Closing notes on tuning

Summary

Exercises

Further reading

11

Controlling Motion with Encoders on Raspberry Pi Pico

Technical requirements

Converting an encoder count into a speed

Loose bolts and nuts

Robot wheel geometry

Encoder geometry

Measuring the speed of each wheel

Fixing the encoder glitches

Using PID to maintain speed and a straight line

The speed control system

Speed control code

Speed controller PID tuning

Driving a known distance

Theory of operation

Code to control distance and speed

Summary

Exercises

Further reading

12

Detecting Orientation with an IMU on Raspberry Pi Pico

Technical requirements

What is an IMU and how to choose one

Components of an IMU

Choosing an IMU module

Connecting the IMU to the robot

Preparing the BNO055

Attaching the BNO055

Wiring the BNO055 to Raspberry Pi Pico

Setting up the software and connecting

Troubleshooting

Calibrating and getting readings

Calibration code

The calibration process

Always face North behavior

CircuitPython code for the face North behavior

Troubleshooting

Making a known turn behavior

Summary

Exercises

Further reading

13

Determining Position Using Monte Carlo Localization

Technical requirements

Creating a training area for our robot

What we will make

How we will make the arena

Tips for cutting

Modeling the space

Representing the arena and robot position as numbers

Serving the arena from the robot

The Bleak library

Creating a Bluetooth LE wrapper library

Showing the robot’s data on the computer screen

Using sensors to track relative pose

Setting up poses

Displaying poses

Moving with collision avoidance

Moving poses with the encoders

Pose movement probabilities

Monte Carlo localization

Generating pose weights from a position

Resampling the poses

Incorporating distance sensors

Tuning and improving the Monte Carlo model

Summary

Exercises

Further reading

14

Continuing Your Journey – Your Next Robot

Technical requirements

A summary of what you have learned in this book

Basic robotics with Raspberry Pi Pico

Extending a Raspberry Pi Pico robot with sensors

Writing CircuitPython behavior code for Raspberry Pi Pico

Planning to extend this robot

Sensors you could add

Interacting with the robot

Chassis and form enhancements

Electronics enhancements

Outputs you could add

Extending the code and behaviors

Planning your next robot

Form, shape, and chassis

Electronics and sensors

Code and behavior

Further suggested areas to learn about

Electronics

Design and manufacturing

Robotic competitions and communities

Robotics systems and code

Summary

Exercises

Further reading

Index

Other Books You May Enjoy

Preface

Robotics is an emerging field with applications in every walk of life. Robotics, and the associated technology, appear to be confined to the well-equipped laboratories of universities and high-tech companies. However, many of the aspects of robotics – building them and programming them – can be learned and practiced in your own home.

The main areas of robotics are as follows:

Structure – the design and building of a mechanical platform

Electronics – sensors, motors, and control circuits

Software – the code for libraries, sensor interactions, and behaviors

This book aims to cover a little of each area, looking at basic CAD design, part fabrication, and assembly of hardware. It introduces some starting digital electronics, such as connections and data buses. It aims to dig a little deeper into the sensors and the code needed to make interesting behaviors using them.

There are robotics books that offer a theoretical robotics introduction; however, the aim of this book is to take you on a journey of practice, fun, and experimentation. This book provides step-by-step applied explanations and images to aid understanding.

Building your own robots in your home is a great way to learn technology skills. This is an experience of technology that replaces impenetrable magic with real-world experience and confidence to build more – anyone with practice can become a robotics wizard too.

Who this book is for

The book is intended for those who would like a practical and step-by-step hands-on introduction to designing, building, and programming robots, using the popular Python programming language. It is also for those who would like to gain an introduction to 3D CAD, robotics sensors, robotics hardware, and robotics behaviors that make use of the sensors and hardware.

This book will be valuable to makers, learners, and developers who want to build robots in their homes or workshops. The book does not require a specialist workshop, and any skills and tools needed will be explained throughout the book.

Those who have written a little code before will find this book useful. You do not need to have any experience with electronics or making things, but you can expect to gain initial experiences while practicing the techniques in this book.

We expect you to have a keen interest in learning more and a little fearlessness in trying robotics experiments. Practical application of the examples within is essential. Getting the most out of this book means being willing to make a real robot and test it.

What this book covers

Chapter 1, Planning a Robot with Raspberry Pi Pico, introduces Raspberry Pi Pico in relation to other robotics main controllers. It shows the advantages of the CircuitPython programming environment and takes you through making an overview plan for a robot build built around Pico. The chapter provides a robot hardware shopping list for the first half of the book, discussing the parts and trade-offs in choosing them.

Chapter 2, Preparing Raspberry Pi Pico, takes you through getting CircuitPython onto Pico, then taking your first steps in writing code with it. It will also cover soldering headers onto Raspberry Pi Pico so it can connect to robot parts.

Chapter 3, Designing a Robot Chassis in FreeCAD, introduces FreeCAD while turning the overview plan into 3D CAD designs. It shows you how to make drawings from the design for building the robot parts.

Chapter 4, Building a Robot around Pico, shows how you can use CAD drawings with hand tools to craft robot parts by cutting and drilling sheet plastic. It guides you in assembling the parts then wiring and connecting the electronics. This chapter is where the robot is first powered on!

Chapter 5, Driving Motors with Raspberry Pi Pico, introduces you to controlling motors with CircuitPython and Raspberry Pi Pico, showing how motors can be used to make line motions and turns and how speed can be controlled. The chapter then shows you how to pull these together into programmed motion sequences.

Chapter 6, Measuring Movement with Encoders on Raspberry Pi Pico, introduces the first robotic sensor in the book with wheel encoders, showing you how to detect wheel movement in code. The chapter covers the Raspberry Pi Pico PIO peripheral as a powerful way to manage these sensors.

Chapter 7, Planning and Shopping for More Devices, prepares you for the next section of the book with distance sensors, Bluetooth LE, and an inertial measurement unit (IMU), with further advice on choosing the devices and how they will be attached. The chapter provides a shopping list for the latter part of the book. You will revisit FreeCAD part design to make sensor mounts, and then use tools to cut them.

Chapter 8, Sensing Distances to Detect Objects with Pico, takes you through attaching and wiring two distance sensors into the robot. The chapter provides information on I2C communication and then shows you how to program the robot to communicate with the sensors. You will then build code for the robot to autonomously avoid walls.

Chapter 9, Teleoperating Raspberry Pi Pico Robot with Bluetooth LE, makes a comparison of wireless connection options, showing why Bluetooth LE was a suitable design choice. You will connect a Bluetooth LE module to the robot, then extend existing code to output sensor data through this connection, and display the output on a smartphone. You will also see how to drive the robot from a smartphone.

Chapter 10, Using the PID Algorithm to Follow Walls, provides an introduction to the PID algorithm, a fundamental building block for sensor/output control behaviors in robotics. We build a wall-following demonstration using a distance sensor, then show you how to tune the PID with smartphone plots via Bluetooth LE.

Chapter 11, Controlling Motion with Encoders on Raspberry Pi Pico, revisits encoders, showing you how to convert their output into units understandable by humans. You will learn how to combine these sensors with the PID algorithm to control motor speeds and drive in a straight line. You will then program the robot to drive a specified distance in a straight line at a specified speed.

Chapter 12, Detecting Orientation with an IMU on Raspberry Pi Pico, introduces the IMU, a sensor that lets you determine the orientation of the robot. The chapter provides a guide on connecting the sensor and calibrating it. You will use the IMU with the PID algorithm for a behavior that makes a robot always face north. Finally, the chapter shows you how to program the robot to make a specified turn using the IMU.

Chapter 13, Determining Location with Monte Carlo, will show you how to program a robot to determine where it is likely to be in an arena. You’ll use plans in the chapter to build a foam board arena and model this arena in code. You are shown how to visualize this space on a computer using Bluetooth LE with Matplotlib. You will then learn about moving robot poses based on sensor input. The chapter shows how multiple robot behaviors can cooperate in the same application. You will be introduced to using probability algorithms in robot motion, making predictions, and refining them.

Chapter 14, Continuing Your Journey – Your Next Robot, provides a summary of the topics learned in the book, with information on digging deeper into each of them. The chapter provides ideas and research areas for you to extend all the aspects of the robot, and then further suggestions to build more ambitious robots and grow your skills. The chapter also recommends robotics communities you could participate in.

To get the most out of this book

You will need to have knowledge of a few Python basics, such as variables, looping, conditionals, and functions. A well-lit and ventilated desk space is recommended for the robot-building aspects of the book. Access to hand tools will help, although you will be shown which tools to shop for. The robot code examples have been tested on CircuitPython 7.2.0 on Raspberry Pi Pico but should work with later versions. The computer code examples were tested on Python 3.9.

Thonny comes with a built-in Python 3.x installation. The Tools | Open System shell menu can be used to install packages in Thonny’s Python.

If you are using the digital version of this book, we advise you to type the code yourself or access the code from the book’s GitHub repository (a link is available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.

Help for this book can be found by:

Raising a bug on the book’s GitHub repository at https://github.com/PacktPublishing/Robotics-at-Home-with-Raspberry-Pi-Pico

Asking via Discord at https://discord.gg/2VHYY3FkXV

Download the example code files

You can download the example code files for this book from GitHub at https://github.com/PacktPublishing/Robotics-at-Home-with-Raspberry-Pi-Pico. If there’s an update to the code, it will be updated in the GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

Download the color images

We also provide a PDF file that has color images of the screenshots and diagrams used in this book. You can download it here: https://packt.link/7x3ku.

Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: To run this code, be sure to send the pio_encoders.py library, the updated robot.py file, and then measure_fixed_time.py.

A block of code is set as follows:

import time

import board

import digitalio

led = digitalio.DigitalInOut(board.LED)

led.direction = digitalio.Direction.OUTPUT

while True:

    led.value = True

    time.sleep(0.5)

    led.value = False

    time.sleep(0.5)

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

>>>

print(Hello, world!)

Hello, World!

>>>

Any command-line input or output is written as follows:

code.py output:

4443 4522

Bold: Indicates a new term, an important word, or words that you see onscreen. For instance, words in menus or dialog boxes appear in bold. Here is an example: Launch Mu Editor, and when it is running, click on the Mode button. From this, select CircuitPython.

Tips or important notes

Appear like this.

Get in touch

Feedback from our readers is always welcome.

General feedback: If you have questions about any aspect of this book, email us at [email protected] and mention the book title in the subject of your message.

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/support/errata and fill in the form.

Piracy: If you come across any illegal copies of our works in any form on the internet, we would be grateful if you would provide us with the location address or website name. Please contact us at [email protected] with a link to the material.

If you are interested in becoming an author: If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, please visit authors.packtpub.com.

Share Your Thoughts

Once you’ve read Robotics at Home with Raspberry Pi Pico, we’d love to hear your thoughts! Please click here to go straight to the Amazon review page for this book and share your feedback.

Your review is important to us and the tech community and will help us make sure we’re delivering excellent quality content.

Download a free PDF copy of this book

Thanks for purchasing this book!

Do you like to read on the go but are unable to carry your print books everywhere? Is your eBook purchase not compatible with the device of your choice?

Don’t worry, now with every Packt book you get a DRM-free PDF version of that book at no cost.

Read anywhere, any place, on any device. Search, copy, and paste code from your favorite technical books directly into your application.

The perks don’t stop there, you can get exclusive access to discounts, newsletters, and great free content in your inbox daily

Follow these simple steps to get the benefits:

Scan the QR code or visit the link below

https://packt.link/free-ebook/9781803246079

Submit your proof of purchase

That’s it! We’ll send your free PDF and other benefits to your email directly

Part 1: The Basics – Preparing for Robotics with Raspberry Pi Pico

In this part, you will take your first steps in learning about Raspberry Pi Pico, then plan and build a robot around it, and get the initial robot code to make the robot move.

This part contains the following chapters:

Chapter 1, Planning a Robot with Raspberry Pi Pico

Chapter 2, Preparing Raspberry Pi Pico

Chapter 3, Designing a Robot Chassis in FreeCAD

Chapter 4, Building a Robot around Pico

Chapter 5, Driving Motors with Raspberry Pi Pico

1

Planning a Robot with Raspberry Pi Pico

When you plan, you create the best chance for a mission’s success. We want to build robots in an achievable way. Let’s start with a plan in mind! We’ll use this plan to explore why Raspberry Pi Pico is a great fit for this and make a shopping list!

In this chapter, you’ll learn about Raspberry Pi Pico’s capabilities. You’ll discover CircuitPython and understand why it is a great language for Raspberry Pi Pico. Additionally, we’ll plan a robot design and understand the trade-offs to make choices about the robot early in the project. We’ll check that our robot fits together, working out the parts and tools you’ll need with suggestions on how to get them.

At the end of the chapter, you’ll have both a plan and parts arriving so that you are ready to build a robot. Additionally, you’ll have a starting process for making other robots and setting yourself up for success with them.

In this chapter, we’ll cover the following main topics:

What is Raspberry Pi Pico, and why is it suitable for robotics?

What is CircuitPython?

Planning a Raspberry Pi Pico robot

Test fitting a Raspberry Pi Pico robot

A recommended shopping list for robot basics

Technical requirements

We’ll go into the necessary hardware and shopping list as we progress further in this chapter. So, in this section, we’ll just focus on what you will need physically and on your computer to get started.

You will require the following:

Some thin cardboard

A ruler, pencil, and scissors

A good web browser with internet access

What is Raspberry Pi Pico, and why is it suitable for robotics?

At the heart of every robot is a controller. Usually, this is a computing device that is responsible for running the code for the robot to perform its tasks and behaviors. Choosing a controller is a key choice in robot design. You can either come from the I have this controller, what can I do with it? perspective or the which controllers have the capabilities I’ll want for a particular robot? perspective.

In this section, we’ll take a closer look at what Raspberry Pi Pico offers as a controller and the trade-offs it’s made. We’ll explore why it is good for robotics and why it could be part of a larger, more interesting system, too.

Additionally, we’ll delve into the details of its interfaces and how they’ll be useful to us.

A microcontroller that runs Python

Let’s start by taking a look at Raspberry Pi Pico, and discover what it has. The following photograph shows Raspberry Pi Pico:

Figure 1.1 – Raspberry Pi Pico

Raspberry Pi Pico, as shown in Figure 1.1, is an RP2040 microcontroller on a Raspberry Pi-designed board. This microcontroller is a small computing device that has been designed to interface closely with hardware. It has a USB connection on the right-hand side for power or programming on a computer. The LED is useful