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

How to make an audio tone control


For the final recipe of this chapter, we'll make a digital tone control that emulates analogue circuits found on portable radios, and so on. Simple analogue tone circuits take the form of an active filter that uses a potentiometer to affect the filter transfer function (that is, emphasizing low/high frequencies—bass/treble—in the audio signal.

Although this recipe illustrates our filter operating in real time, it isn't the most efficient way of filtering digital audio. The audio codec includes its own DSP processing block, and this can be programmed to produce similar results more efficiently. We'll refer to this recipe as codecDemo_c7v3.

Getting ready

The high- and low-pass FIR filter coefficients that we need for this recipe are found using MATLAB. We've chosen the pass and stop bands that are shown in the following screenshot:

How to do it…

  1. Clone codecDemo_c7v2 from the Designing a low-pass digital filter recipe and name the new folder codecDemo_c7v3.

  2. Use the...