Real-Time Digital Signal Processing from MATLAB to C with the TMS320C6x DSPs

Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow

• Publisher: CRC Press
• Year: 2016
• ISBN:
  9781351848268
• Edition: 3
• Topic: Informatik
• Subtopic: Computertechnik

This updated edition gives readers hands-on experience in real-time DSP using a practical, step-by-step framework that also incorporates demonstrations, exercises, and problems, coupled with brief overviews of applicable theory and MATLAB applications. Organized in three sections that cover enduring fundamentals and present practical projects and invaluable appendices, this new edition provides support for the most recent and powerful of the inexpensive DSP development boards currently available from Texas Instruments: the OMAP-L138 LCDK. It includes two new real-time DSP projects, as well as three new appendices: an introduction to the Code Generation tools available with MATLAB, a guide on how to turn the LCDK into a portable battery-operated device, and a comparison of the three DSP boards directly supported by this edition.

Section II:
Projects

Chapter 10

Project 1: Guitar Special Effects

10.1 Introduction to Projects

SINCE this is the first chapter in the Projects section, let’s explain how this part of the book differs from the previous section. All the the previous chapters cover topics we have called the “enduring fundamentals” of DSP. The topics were relatively broad, and the examples shown were meant only to illustrate that particular topic.

In the Projects section, we change our focus somewhat; we will now provide in each chapter at least one fully functional version of an interesting DSP application we have found to be popular with students over the years. In particular, the two general areas students seem to be drawn to when first learning DSP are audio (such as the special effects of this chapter and the graphics equalizer of the next chapter) and communications (such as the various receiver and transmitter projects of later chapters). While we provide fully functional code to get you started, we intentionally leave it to you to implement and improve the applications further. That’s why they’re called projects!

We remind the reader that most of the code shown for the projects in this and the following chapters is intentionally not fully optimized, because maximally efficient code is often very hard to understand—and our goal is for you to understand the code! You may want to explore ways in which you can improve the efficiency of these projects on your own. This first project chapter involves concepts that are fairly easy to understand; later project chapters progress to increasingly more involved examples.

10.2 Theory

10.2.1 Background

Special effects for electric guitars (and microphones) are a fun application of DSP. You can create all sorts of interesting sound variations quite easily with fairly simple DSP algorithms. Some of the more familiar effects include echo, chorus, flanger, phasing, reverb, tremelo, frequency translation, subharmonic generation, ring modulation, fuzz, compression/expansion, equalization, noise gating, and others. Whether you know them by these common names or not, you probably know what each of these effects “sounds” like if you’ve listened to even a moderate amount of popular music over the past 40 years or so. We will discuss a representative group of these effects in this chapter.

Spe...