Get started with MicroPython on Raspberry Pi Pico: The Official Raspberry Pi Pico Guide

Get started with MicroPython

on Raspberry Pi Pico,

2nd Edition

Get started with MicroPython on Raspberry Pi Pico

by Gareth Halfacree and Ben Everard

ISBN: 978-1-912047-29-1

Copyright © 2024 Gareth Halfacree and Ben Everard

Printed in the United Kingdom

Published by Raspberry Pi Ltd., 194 Science Park, Cambridge, CB4 0AB

Editors: Brian Jepson, Liz Upton

Technical Editors: Brian Jepson, Jo Hinchliffe

Interior Designer: Sara Parodi

Production: Nellie McKesson

Photographer: Brian O’Halloran

Illustrator: Sam Alder

Graphics Editor: Natalie Turner

Publishing Director: Brian Jepson

Head of Design: Jack Willis

CEO: Eben Upton

January 2025: Second Edition, Second Printing

June 2024: Second Edition

January 2021: First Edition

The publisher, and contributors accept no responsibility in respect of any omissions or errors relating to goods, products or services referred to or advertised in this book. Except where otherwise noted, the content of this book is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)

Welcome

You might think of computers as things you stick on your desk and type on. That is certainly one type of computer, but it’s not the only type. In this book, we’re looking at microcontrollers — small processing units with a bit of memory that are good at controlling other hardware. You probably have lots of microcontrollers in your house already.

There’s a good chance your washing machine is controlled by a microcontroller; maybe your watch is; you might find one in your coffee machine or microwave. All these microcontrollers already have software running on them and the manufacturers make it hard to make any kind of change to that software.

A Raspberry Pi Pico, on the other hand, is a microcontroller that you can easily program (and reprogram!) over a USB connection. In this book, we’ll look at how to get started with Pico and how to make it work with other electronic components. By the end of the book, you’ll know how to create your own programmable electronic contraptions. What you do with them is up to you.

You can find this book’s example code, errata, and other resources in its GitHub repository at rptl.io/pico-resources-2e. If you’ve found what you believe is a mistake or error in the book, please let us know by using our errata submission form at rptl.io/pico-errata-2e.

About the authors

Gareth Halfacree is a freelance technology journalist, writer, and former system administrator in the education sector. With a passion for open-source software and hardware, he was an early adopter of the Raspberry Pi platform and has written several publications on its capabilities and flexibility. He can be found on Mastodon as @[email protected] or via his website at freelance.halfacree.co.uk.

Ben Everard is a geek who has stumbled into a career that lets him play with new hardware. As the editor of HackSpace magazine (hsmag.cc), he spends more time than he really should experimenting with the latest (and not-so latest) DIY tech. He lives in Bristol with his wife and two daughters in a house that’s slowly filling up with electronics equipment and 3D printers.

Colophon

Raspberry Pi is an affordable way to do something useful, or to do something fun.

Democratising technology — providing access to tools — has been our motivation since the Raspberry Pi project began. By driving down the cost of general-purpose computing to below $5, we’ve opened up the ability for anybody to use computers in projects that used to require prohibitive amounts of capital. Today, with barriers to entry being removed, we see Raspberry Pi computers being used everywhere from interactive museum exhibits and schools to national postal sorting offices and government call centres. Kitchen table businesses all over the world have been able to scale and find success in a way that just wasn’t possible in a world where integrating technology meant spending large sums on laptops and PCs.

Raspberry Pi removes the high entry cost to computing for people across all demographics: while children can benefit from a computing education that previously wasn’t open to them, many adults have also historically been priced out of using computers for enterprise, entertainment, and creativity.

Raspberry Pi eliminates those barriers.

Raspberry Pi Press

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Raspberry Pi Press is your essential bookshelf for computing, gaming, and hands-on making. We are the publishing imprint of Raspberry Pi Ltd. From building a PC to building a cabinet, discover your passion, learn new skills, and make awesome stuff with our extensive range of books and magazines.

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The MagPi is the official Raspberry Pi magazine. Written for the Raspberry Pi community, it is packed with Pi-themed projects, computing and electronics tutorials, how-to guides, and the latest community news and events.

Chapter 1

Get to know your Raspberry Pi Pico

Get acquainted with your powerful new microcontroller board and learn how to attach pin headers and install MicroPython to program it

Raspberry Pi Pico-family boards are miniature marvels, putting the same technology that underpins everything from smart home systems to industrial factories in the palm of your hand. Whether you’re looking to learn about the MicroPython programming language, take your first steps in physical computing, or want to build a hardware project, Pico — and the amazing community behind it — will support you every step of the way.

Raspberry Pi Pico devices are microcontroller development boards. They’re designed for experimenting with physical computing using a special type of processor: a microcontroller. The size of a stick of gum, the Pico boards pack a surprising amount of power thanks to the chip at their centre: an RP2040 microcontroller for Pico and Pico W, and an RP2350 for Pico 2 and Pico 2 W.

Raspberry Pi Pico boards aren’t designed to replace Raspberry Pi, which is an entirely different class of device known as a single-board computer. You might use Raspberry Pi to play games, write software, or browse the web. Raspberry Pi Pico is designed for physical computing projects, where it is used to control anything from LEDs and buttons to sensors, motors, and even other microcontrollers.

Throughout this book you’ll learn all about the Raspberry Pi Pico boards, but the skills you learn will also apply to any development board based around the RP2040 or RP2350 microcontrollers — and even other devices, so long as they are compatible with the MicroPython programming language.

A guided tour of Raspberry Pi Pico 2

A Raspberry Pi Pico-family microcontroller — ‘Pico’ for short — is a lot smaller than even Raspberry Pi Zero, the most compact of Raspberry Pi’s single-board computers. Despite this, it includes a lot of features — all accessible using the pins around the edge of the board. The second-generation Pico series is available in two versions, Pico 2 and Pico 2 W; you’ll see the difference between the two later. If you have an original Pico or Pico W, the layout of the board is generally the same.

Figure 1-1 shows Raspberry Pi Pico 2 as seen from above. If you look at the longer edges, you’ll see gold-coloured sections with small holes. These are the pins which provide the RP2040 microcontroller with connections to the outside world — known as input/output (IO).

Figure 1-1: The top of the board

The pins on your Pico 2 are very similar to the pins that make up the general-purpose input/output (GPIO) header on a Raspberry Pi — but while most Raspberry Pi single-board computers come with the physical metal pins already attached, Pico boards do not.

If you want to buy a Pico 2 with headers mounted, look for Raspberry Pi Pico 2 or Pico 2 W with headers. There’s a good reason to offer models without headers attached: look at the outer edge of the circuit board and you’ll see it’s bumpy, with little circular cut-outs (Figure 1-2).

These bumps create what is called a castellated circuit board, which can be soldered on top of other circuit boards without using any physical metal pins. It’s very helpful in builds where you need to keep the height to a minimum, making for a smaller finished project. If you buy an off-the-shelf gadget powered by a Pico-family microcontroller, it’ll almost certainly be fitted using the castellations.

The holes just inwards from the bumps are to accommodate 2.54mm male pin headers. You’ll recognise them as the same type of pins used on the bigger Raspberry Pi’s GPIO header. By soldering these in place pointing downwards, you can push your Pico into a solderless breadboard to make it easy to connect and disconnect new hardware — great for experiments and rapid prototyping!

The chip at the centre of your Pico 2 (Figure 1-3) is an RP2350 microcontroller. This is a custom integrated circuit (IC), designed and built by Raspberry Pi to operate as the brains of your Pico and other microcontroller-based devices. If you look at it closely, you’ll see a Raspberry Pi logo etched into the top of the chip along with a series of letters and numbers which let engineers track when and where the chip was made.

Figure 1-2: Castellation

Figure 1-3: RP2350 chip

At the top of your Pico is a micro USB port (Figure 1-4). This provides power to make your Pico run, and also sends and receives data that lets your Pico talk to a Raspberry Pi or another computer via its USB port. This is how you’ll load programs onto your Pico.

Figure 1-4: micro USB port

If you hold your Pico up and look at the micro USB port head-on, you’ll see it’s shaped so it’s narrower at the bottom and wider at the top. Take a micro USB cable, and you’ll see its connector is the same.

The micro USB cable will only go into the micro USB port on your Pico one way up. When you’re connecting it, make sure to line the narrow and wide sides up the right way around — you could damage your Pico if you try to brute-force the micro USB cable in the wrong way up!

Just below the micro USB port is a small button marked ‘BOOTSEL’, shown in Figure 1-5. ‘BOOTSEL’ is short for boot selection, which switches your Pico between two start-up modes when it’s first switched on. You’ll use the boot selection button later, as you get your Pico ready for programming.

At the bottom of your Pico are three smaller gold pads with the word ‘DEBUG’ above them (Figure 1-6). These are designed for debugging, or finding errors, in programs running on the Pico, using a special tool called a debugger. You won’t need to use the debug header at first, but you may find it useful as you write larger and more complicated programs. On some Raspberry Pi Pico models, the debug pads are replaced by a small, three-pin connector.

Figure 1-5: Boot selection button

Figure 1-6: Debug pads

Turn your Pico over and you’ll see the underside has writing on it (Figure 1-7). This printed text is known as a silk-screen layer, and labels each of the pins with its core function. You’ll see things like ‘GP0’ and ‘GP1’, ‘GND’, ‘RUN’, and ‘3V3’. If you ever forget which pin is which, these labels will tell you — but you won’t be able to see them when the Pico is pushed into a breadboard, so we’ve printed full pinout diagrams in this book for easier reference.

You might have noticed that not all the labels line up with their pins. The small holes at the top and bottom of the board are mounting holes, designed to allow you to fix your Pico to projects more permanently, using screws or nuts and bolts. Where the holes get in the way of the labelling, the labels are pushed further up or down the board: looking at the top-right. So ‘VBUS’ is the first pin on the left, ‘VSYS’ the second, and ‘GND’ the third.

Figure 1-7: Labelled underside

You’ll also see some flat, gold pads labelled with ‘TP’ and a number. These are test points, and are designed for engineers to quickly check that a Raspberry Pi Pico is working after it has been assembled at the factory — you won’t be using them yourself. Depending on the test pad, the engineer might use a multimeter or an oscilloscope to check that your Pico is working properly before it’s packaged up and shipped to you.

If you have a Raspberry Pi Pico 2 W, you’ll find another piece of hardware on the board: a silver metal rectangle (Figure 1-8). This is a shield for a wireless module, like the one on Raspberry Pi 4 and Raspberry Pi 5, which can be used to connect your Pico to a Wi-Fi network or to Bluetooth devices. It’s connected to a small antenna which sits at the very bottom of the board — which is why you’ll find the debug pads or connector closer to the middle of the board on Raspberry Pi Pico 2 W.

Figure 1-8: The Raspberry Pi Pico 2 W wireless module and antenna

Soldering the headers

Look at a standard Raspberry Pi Pico-family board, and you’ll see it is completely flat. There are no metal pins like you’d find on the GPIO header of your Raspberry Pi or on the Pico-family boards with headers.

The easiest way to use a Pico is to attach it to a solderless breadboard —for that, you’ll need to attach pin headers. You’ll need a soldering iron with a stand, some solder, a cleaning sponge, your Pico, and two 20-pin 2.54 mm male header strips. You can use a solderless breadboard to make the process easier.

Although this section shows how to solder headers to an original Raspberry Pi Pico, the process is the same for a Pico 2.

Sometimes 2.54 mm headers are provided in strips longer than 20 pins. If yours are longer, just count 20 pins in from one end and look at the plastic between the 20th and 21st pins: you’ll see it has a small indentation at either side.