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

Multithreaded programs using event flags


This recipe will illustrate how to use CMSIS-RTOS to make an LED blink. We'll define two tasks or threads. The job of one task is to switch the LED ON, and the other one is to switch it OFF. The ON and OFF events are triggered by the tasks sending messages to each other. CMSIS-RTOS supports a number of intertask-communication strategies; our program uses event flags. We can illustrate our program using a state diagram, as follows:

We'll call our first recipe, RTOS_Blinky_c8v0.

How to do it…

Create a new project (in a new folder) named RTOS_Binky and use the Run-Time Environment manager to select Board SupportLED (API) and CMSISKeil RTX as shown in the following screenshot. As usual, we can select Resolve to fix the warning messages. Note that this RTE is the same as the one that we introduced in Chapter 2, C Language Programming.

  1. Create a new file named RTXBlinky.c, and create a skeleton by adding boilerplate code for SystemClock_Config(), and so...