Book Image

ARM® Cortex® M4 Cookbook

By : Mark Fisher, Dr. Mark Fisher
Book Image

ARM® Cortex® M4 Cookbook

By: Mark Fisher, Dr. Mark Fisher

Overview of this book

Embedded microcontrollers are at the core of many everyday electronic devices. Electronic automotive systems rely on these devices for engine management, anti-lock brakes, in car entertainment, automatic transmission, active suspension, satellite navigation, etc. The so-called internet of things drives the market for such technology, so much so that embedded cores now represent 90% of all processor’s sold. The ARM Cortex-M4 is one of the most powerful microcontrollers on the market and includes a floating point unit (FPU) which enables it to address applications. The ARM Cortex-M4 Microcontroller Cookbook provides a practical introduction to programming an embedded microcontroller architecture. This book attempts to address this through a series of recipes that develop embedded applications targeting the ARM-Cortex M4 device family. The recipes in this book have all been tested using the Keil MCBSTM32F400 board. This board includes a small graphic LCD touchscreen (320x240 pixels) that can be used to create a variety of 2D gaming applications. These motivate a younger audience and are used throughout the book to illustrate particular hardware peripherals and software concepts. C language is used predominantly throughout but one chapter is devoted to recipes involving assembly language. Programs are mostly written using ARM’s free microcontroller development kit (MDK) but for those looking for open source development environments the book also shows how to configure the ARM-GNU toolchain. Some of the recipes described in the book are the basis for laboratories and assignments undertaken by undergraduates.
Table of Contents (16 chapters)
ARM Cortex M4 Cookbook
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Handling interrupts


This section illustrates an approach that improves on polling. We replace the busy-wait loop and instead configure the USART peripheral to generate an interrupt signal when a new character is received by the input data register (IDR). The interrupt signal causes a special function, known as an interrupt service routine (ISR), to be called, and this, in turn, reads the IDR and clears the interrupt signal. We illustrate this approach by a simple recipe called helloISR_c3v0.

Getting ready

Two small changes to SER_Init() are needed to configure UART4 so that interrupts are generated when a character is received. The value written to CR1 is changed from 0x200C to 0x202C, thereby setting bit-5 (RXNEIE), and the Nested Vectored Interrupt Controller (the NVIC is an ARM interrupt-dedicated peripheral close to the Cortex-M4 processor) is configured for UART4 as follows:

/*--------------------------------------------------------------
 *       SER_Init:  Initialize Serial Interface...