REAL-TIME DIGITAL SIGNAL PROCESSING from MATLAB to C with the TMS320C6x DSK

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1 REAL-TIME DIGITAL SIGNAL PROCESSING from MATLAB to C with the TMS320C6x DSK Thad B. Welch United States Naval Academy, Annapolis, Maryland Cameron KG. Wright University of Wyoming, Laramie, Wyoming Michael G. Morrow University of Wisconsin, Madison, Wisconsin (CoC\ Taylor &. Francis ^ ^ J Taylor & Francis Group Boca Raton London New York A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Croup, the academic division of T&F Informa pic.

2 Contents Preface Acknowledgments xxxi xxxiii Enduring Fundamentals 1 1 Introduction and Organization Why Do You Need This Book? Other DSP Books Demos and DSP Hardware Philosophy of This Book Real-Time DSP How to Use This Book Transition to Real-Time Chapter Coverage Hardware and Software Installation Reading Program Listings Get Started 10 2 Sampling and Reconstruction Theory Choosing a Sampling Frequency Input/Output Issues: Samples or Frames? The Talk-Through Concept windsk6 Demonstration Starting windsk Talk-Thru Application Talk-Through Using Windows Talk-Through Using MATLAB and Windows Talk-Through Using MATLAB Only Talk-Through Using MATLAB DSK Implementation in C Follow-On Challenges 23 3 FIR Digital Filters Theory Traditional Notation FIR Filters Compared to IIR Filters Calculating the Output of a Filter 26 xi

3 CONTENTS 3.2 windsk6 Demonstration Graphic Equalizer Application Notch Filter Application Audio Effects Application MATLAB Implementation Built-in Approach Creating Your Own Filter Algorithm DSK Implementation in C Brute Force FIR Filtering in C: Part Brute Force FIR Filtering in C: Part Circular Buffered FIR Filtering Follow-On Challenges 44 IIR Digital Filters Theory windsk6 Demonstration: Notch Filter Application MATLAB Implementation Filter Design and Analysis IIR Filter Notation Block Diagrams Built-in Approach Creating Your Own Filter Algorithm, DSK Implementation in C Brute Force IIR Filtering More Efficient IIR Filtering Follow-On Challenges 70 Periodic Signal Generation Theory Periodic Signals in DSP Signal Generation windsk6 Demonstration Arbitrary Waveform DTMF MATLAB Implementation Direct Digital Synthesizer Technique Table Lookup Technique DSK Implementation in C : Direct Digital Synthesizer Technique Table Lookup Technique Table Lookup Technique with Table Creation Digital Resonator Technique Follow-On Challenges 90 Frame-Based DSP Theory Drawbacks of Sample-Based DSP What Is a Frame? windsk6 Demonstration MATLAB Implementation DSK Implementation in C 95

4 CONTENTS xiii Triple Buffering A Frame-Based DSP Example Using Direct Memory Access Summary of Frame-Based Processing Follow-On Challenges Digital Filters Using Frames Theory Ill 7.2 windsk6 Demonstration Ill 7.3 MATLAB Implementation Ill 7.4 DSK Implementation in C Ill Understanding the FIR Process for Frames How to Avoid the "Edge" Problems Explanation of the C Code Follow-On Challenges The Fast Fourier Transform Theory Defining the FFT The Twiddle Factors The FFT Process Bit-Reversed Addressing Using the FFT for Filtering Avoiding Circular Convolution Real-Time Fast Convolution windsk6 Demonstration MATLAB Implementation DSK Implementation in C Follow-On Challenges Spectral Analysis and Windowing Theory Power Spectrum of a Signal The Need for Windowing Window Characteristics windsk6 Demonstration MATLAB Implementation DSK Implementation in C Conclusion Follow-On Challenges '. 141 Projects Project 1: Guitar Special Effects Introduction to Projects Theory Background How the Effects Work windsk6 Demonstration MATLAB Implementation FIR Comb Filter 158

5 xiv CONTENTS IIR Comb Filter Notch Filter Flanger Tremelo DSK Implementation in C Real-Time Comb Filters Other Real-Time Special Effects Follow-On Challenges Project 2: Graphic Equalizer Theory....' windsk6 Demonstration Graphic Equalizer Application Effect of the Graphic Equalizer MATLAB Implementation DSK Implementation in C Applying Gain to Filter Bands GEL File Slider Control Follow-On Challenges Project 3: Peak Program Meter Theory windsk6 Demonstration: commdsk MATLAB Implementation DSK Implementation in C Example PPM Code DSK LED Control Another PPM Code Version Follow-On Challenges Project 4: AM Transmitter Theory windsk6 Demonstration MATLAB Implementation DSK Implementation in C Follow-On Challenges Project 5: AM Receiver Theory Envelope Detector The Hilbert-Based AM Receiver windsk6 Demonstration MATLAB Implementation DSK Implementation in C Follow-On Challenges Project 6: Phase-Locked Loop Theory windsk6 Demonstration MATLAB Implementation PLL Simulation 216

6 CONTENTS xv A Few Updates to the MATLAB Implementation DSK Implementation in C Components of the PLL System Testing Follow-On Challenges Project 7: Digital Communications Transmitters Theory Random Data and Symbol Generation BPSK Using Antipodal Rectangularly Shaped Bits BPSK Using Impulse Modulated Raised-Cosine Shaped Bits windsk6 Demonstration commdsk: Unfiltered BPSK commdsk: Raised-Cosine Filtered BPSK MATLAB Implementation Rectangular Shaped BPSK Signal Generator Impulse Modulated Raised-Cosine BPSK Signal Generator DSK Implementation in C A Rectangular Pulse Shaped BPSK Transmitter A Raised-Cosine Pulse Shaped BPSK Transmitter Summary of Real-Time Code Follow-On Challenges Project 8: Digital Communications Receivers Theory : The Output of the Matched Filter The Eye-Pattern Maximum Likelihood Timing Recovery windsk6 Demonstration MATLAB Implementation DSK Implementation in C Components of the Digital Receiver System Testing Follow-On Challenges 268 Appendices 271 A Code Composer Studio: A Brief Tutorial 273 A.I Introduction 273 A.2 Starting Code Composer Studio 273 A.3 Needed Files 277 A.4 Creating a New Project 278 A.5 Opening Existing Projects 280 A.6 Adding Files to a Project 281 A.7 Project Options 284 A.8 Building the Project 285 A.9 Loading the Program on the DSK 287 A.10 Running the Program on, the DSK 290 A.ll Get to Know CCS 291 A.12 Typical Files for Our CCS Projects 291

7 xvi CONTENTS B DSP/BIOS 295 B.I Introduction 295 B.I.I DSP/BIOS Major Features 295 B.1.2 DSP/BIOS Threads 295 B.2 Using the DSP/BIOS Scheduler 296 B.2.1 Adding a PRD Function 297 B.2.2 Adding a HWI Function 297 B.2.3 Adding a SWI Function 298 B.2.4 Adding a TSK Function 299 B.2.5 Real-Time Analysis Tools 299 B.3 A DSP/BIOS Talk-Through Application for the 6711 DSK 300 B.3.1 main.c 300 B.3.2 hwi.c 301 B.3.3 DSP/BIOS HWI Configuration 301 B.3.4 DSP/BIOS Serial Port Configuration 302 B.3.5 ' Source Code 302 B.4 Modification Needed for the Stereo Codecs 303 B.4.1 main.c 303 B.4.2 hwi.c 303 B.4.3 DSP/BIOS HWI Configuration 304 B.4.4 DSP/BIOS Serial Port Configuration 304 B.5 A DSP/BIOS Talk-Through Application for the 6713 DSK 305 B.5.1 main.c 305 B.5.2 hwi.c 306 B.5.3 DSP/BIOS HWI Configuration 306 B.5.4 DSP/BIOS Serial Port Configuration 307 B.5.5 Source Code 307 C Numeric Representations 311 C.I Endianness 311 C.2 Integer Representations 312 C.3 Integer Division and Rounding 313 C.4 Floating-Point Representations 314 C.5 Fixed-Point Representations 316 C.6 Summary of Numeric Representations 317 D TMS320C6x Architecture 319 D.I Computer Architecture Basics 319 D.I.I Instruction Set Architecture 320 D.1.2 Register Architectures 320 D.I.3 Memory Architectures 321 D.1.4 Fetch-Execute Model 322 D.I.5 Pipelining 322 D.I.6 Single- versus Multiple-Issue 325 D.I.7 Scheduling 325 D.2 TMS320C671x Architecture 326 D.2.1 Memory System 328 D.2.2 Pipeline and Scheduling 329 D.2.3 Peripherals 329 D.2.4 Host Port Interface :. 330

8 CONTENTS xvii E Related Tools for DSKs 331 E.I Introduction 331 E.2 Windows Control Applications 331 E.2.1 The Basic Windows Control Application 332 E.2.2 Creating an Oscilloscope Application 333 E.2.3 Creating a Spectrum Analyzer Application 339 E.3 MATLAB Exports 339 E.3.1 Exporting Direct-Form II Implementations 340 E.3.2 Exporting Second Order Section Implementations 341 E.4 MATLAB Real-Time Interface 342 F Programming Perils and Pitfalls 343 F.I Debug versus Release Builds 343 F.2 The Volatile Keyword 343 F.3 Function Prototypes and Return Types 344 F.4 Arithmetic Issues 345 F.5 Controlling the Location of Variables in Memory 346 F.6 Real-Time Schedule Failures 347 G Abbreviations 349 References 355 Index 361

Digital Signal Processing

Real-Time Second Edition Digital Signal Processing from MATLAB to C with the TMS320C6X DSPs Thad B. Welch Boise State University, Boise, Idaho Cameron H.G. Wright University of Wyoming, Laramie, Wyoming