Stephen Smith - RP2040 Assembly Language Programming: ARM Cortex M0+ on the Raspberry Pi Pico

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There is an explosion of DIY electronics projects, largely fueled by the Arduino-based microcontrollers and Raspberry Pi computers. Electronics projects have never been easier to build, with hundreds of inexpensive modular components to choose from. People are designing robots, home monitoring and security systems, game devices, musical instruments, audio systems, and a lot more. The Raspberry Pi Pico is the Raspberry Pi Foundations entry into the Arduino-style microcontroller market. A regular Raspberry Pi computer runs Linux and typically costs from $35 to $100 depending on memory and accessories. The Raspberry Pi Pico costs $4 and doesnt run an operating system.

To power the Raspberry Pi Pico, the Raspberry Pi Foundation designed a custom system on a chip (SoC), called the RP2040, containing dual ARM Cortex-M0+ CPUs along with a raft of device controller components. This combination of a powerful CPU and ease of integration has made this a great choice for any DIY project. Further, Raspberry sells the RP2040 chips separately, and other companies such as Seeed Studio, Adafruit, and Pimoroni are selling their own versions of this microcontroller with extra built-in features like Bluetooth or Wi-Fi. You can even buy RP2040 chips yourself for $1 each and build your own board.

At the basic level, how are these microcontrollers programmed? What provides the magical foundation for all the great projects that people build on them? Raspberry provides an SDK for C programmers as well as support for programming in MicroPython. This book answers these questions and delves into how these are programmed at the bare metal level and provides insight into the RP2040s architecture.

Assembly Language is the native, lowest-level way to program a computer. Each processing chip has its own Assembly Language. This book covers programming the ARM Cortex-M0+ 32-bit processor. To learn how a computer works, learning Assembly language is a great way to get into the nitty-gritty details. The popularity and low cost of microcontrollers like the Raspberry Pi Pico provide ideal platforms to learn advanced concepts in computing.

Even though all these devices are low powered and compact, theyre still sophisticated computers with a multicore processor, programmable I/O processors, and integrated hardware controllers. Anything learned about these devices is directly relevant to any gadget with an ARM processor, which by volume is the number one processor on the market today.

In this book, we cover how to program ARM Cortex-M0+ processors at the lowest level, operating as close to the hardware as possible. You will learn the following:

The simplest way to learn these tasks is with a Raspberry Pi Pico connected to a Raspberry Pi running the Raspberry Pi OS, a version of Linux. This provides all the tools needed to learn Assembly Language programming. All the software required for this book is open source and readily available on the Raspberry Pi.

This book contains many working programs to play with, use as a starting point, or study. The only way to learn programming is by doing, so dont be afraid to experiment, as it is the only way to learn.

Even if Assembly programming isnt used in your day-to-day life, knowing how the processor works at the Assembly Language level and knowing the low-level binary data structures will make you a better programmer in all other areas. Knowing how the processor works will let you write more efficient C code and can even help with Python programming.

Enjoy your introduction to Assembly Language. Learning it for one processor family helps with learning and using any other processor architectures encountered throughout your career.

The source code for the example code in the book is located on the Apress GitHub site at the following URL:

https://github.com/Apress/RP2040-Assembly-Language-Programming

The code is organized by chapter and includes answers to the programming exercises.

No book is ever written in isolation. I want to especially thank my wife, Cathalynn Labont-Smith, for her support, encouragement, and expert editing.

I want to thank all the good folk at Apress who made the whole process easy and enjoyable. A special shout-out to Jessica Vakili, my coordinating editor, who kept the whole project moving quickly and smoothly. Thanks to Aaron Black, senior editor, who recruited me and got the project started. Thanks to Stewart Watkiss, my technical reviewer, who helped make this a far better book.