John Wiley - Digital Signal Processing and Applications Using the ARM Cortex M4

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Library of Congress Cataloging-in-Publication Data:

Reay, Donald (Donald S.), author.

Digital signal processing using the ARM Cortex-M4 / Donald Reay.

pages cm

Includes bibliographical references and index.

ISBN 978-1-118-85904-9 (pbk.)

1. Signal processingDigital techniques. 2. ARM microprocessors. I. Title.

TK5102.9.R4326 2015

621.3822dc23

2015024771

To Reiko

This book continues the series started in 1990 by Rulph Chassaing and Darrell Horning's Digital Signal Processing with the TMS320C25, which tracked the development of successive generations of digital signal processors by Texas Instruments. More specifically, each book in the series up until now has complemented a different inexpensive DSP development kit promoted for teaching purposes by the Texas Instruments University Program. A consistent theme in the books has been the provision of a large number of simple example programs illustrating DSP concepts in real time, in an electrical engineering laboratory setting.

It was Rulph Chassaing's belief, and this author continues to believe, that hands-on teaching of DSP, using hardware development kits and laboratory test equipment to process analog audio frequency signals, is a valuable and effective way of reinforcing the theory taught in lectures.

The contents of the books, insofar as they concern fundamental concepts of digital signal processing such as analog-to-digital and digital-to-analog conversion, finite impulse response (FIR) and infinite impulse response (IIR) filtering, the Fourier transform, and adaptive filtering, have changed little. Every academic year brings another cohort of students wanting to study this material. However, each book has featured a different DSP development kit.

In 2013, Robert Owen suggested to me that hands-on DSP teaching could be implemented using an inexpensive ARM Cortex-M4 microcontroller. I pointed out that a Texas Instruments C674x processor was very significantly more computationally powerful than an ARM Cortex-M4. But I also went ahead and purchased a Texas Instruments Stellaris LaunchPad. I constructed an audio interface using a Wolfson WM8731 codec and successfully ported the program examples from my previous book to that hardware platform.

This book is aimed at senior undergraduate and postgraduate electrical engineering students who have some knowledge of C programming and linear systems theory, but it is intended, and hoped, that it may serve as a useful resource for anyone involved in teaching or learning DSP and as a starting point for teaching or learning more.

I am grateful to Robert Owen for first making me aware of the ARM Cortex-M4; to Khaled Benkrid at the ARM University Program and to the Royal Academy of Engineering for making possible a six-month Industrial Secondment to ARM during which teaching materials for the STM32f01 platform were developed; to Gordon McLeod and Scott Hendry at Wolfson Microelectronics for their help in getting the Wolfson Pi audio card to work with the STM32f01 Discovery; to Sean Hong, Karthik Shivashankar, and Robert Iannello at ARM for all their help; to Joan Teixidor Buixeda for helping to debug the program examples; to Cathy Wicks at the TI University Program and Hieu Duong at CircuitCo for developing the audio booster pack; and to Kari Capone and Brett Kurzman at Wiley for their patience. But above all, I thank Rulph Chassaing for inspiring me to get involved in teaching hands-on DSP.

Donald S. Reay

Edinburgh

2015

Traditionally, real-time digital signal processing (DSP) has been implemented using specialized and relatively expensive hardware, for example, digital signal processors or field-programmable gate arrays (FPGAs). The ARM Cortex-M4 processor makes it possible to process audio in real time (for teaching purposes, at least) using significantly less expensive, and simpler, microcontrollers.

The ARM Cortex-M4 is a 32-bit microcontroller. Essentially, it is an ARM Cortex-M3 microcontroller that has been enhanced by the addition of DSP and single instruction multiple data (SIMD) instructions and (optionally) a hardware floating-point unit (FPU). Although its computational power is a fraction of that of a floating-point digital signal processor, for example, the Texas Instruments C674x, it is quite capable of implementing DSP algorithms, for example, FIR and IIR filters and fast Fourier transforms for audio signals in real-time.

A number of semiconductor manufacturers have developed microcontrollers that are based on the ARM Cortex-M4 processor and that incorporate proprietary peripheral interfaces and other IP blocks. Many of these semiconductor manufacturers make available very-low-cost evaluation boards for their ARM Cortex-M4 microcontrollers. Implementing real-time audio frequency example programs on these platforms, rather than on more conventional DSP development kits, constitutes a reduction of an order of magnitude in the hardware cost of implementing hands-on DSP teaching. For the first time, students might realistically be expected to own a hardware platform that is useful not only for general microcontroller/microprocessor programming and interfacing activities but also for implementation of real-time DSP.