Digital signal processing techniques have become the method of choice in signal processing as digital computers have increased in speed, convenience, and availability. As microprocessors have become less expensive and more powerful, the number of DSP applications which have become commonly available has exploded. Thus, some DSP microprocessors can now be considered commodity products. Perhaps the most visible high volume DSP applications are the so called multimedia applications in digital audio, speech processing, digital video, and digital communications. In many cases, these applications contain embedded digital signal processors where a host CPU works in a loosely coupled way with one or more DSPs to control the signal flow or DSP algorithm behavior at a real-time rate.

Unfortunately, the development ofsignal processing algorithms for these specialized embedded DSPs is still difficult and often requires specialized training in a particular assembly language for the target DSP. The tools for developing new DSP algorithms are slowly improving as the need to design new DSP applications more quickly becomes important.

The C language is proving itself to be a valuable programming tool for real- time computationally intensive sof tware tasks. C has high-level language capabilities (such as structures, arrays, and functions) as well as low-level assembly language capabilities (such as bit manipulation, direct hardware input/output, and macros) which makes C an ideal language f or embedded DSP. Most of the manufacturers of digital signal processing devices (such as Texas Instruments, AT&T, Motorola, and Analog Devices) provide C compilers, simulators, and emulators for their parts. These C compilers offer standard C language with extensions for DSP to allow for very efficient code to be generated. For example, an inline assembly language capability is usually provided in order to optimize the performance of time critical parts of an application. Because the majority of the code is C, an application can be transferred to another processor much more easily than an all assembly language program.

This book is constructed in such a way that it will be most useful to the engineer who is familiar with DSP and the C language, but who is not necessarily an expert in both. All of the example programs in this book have been tested using standard C c ompilers in the UNIX and MS- DOS programming environments. In addition, the examples have been compiled utilizing the real-time programing tools of specific real- time embedded DSP microprocessors (Analog Devices ADSP-21020 and ADSP- 21062; Texas Instr ument's TMS320C30 and TMS320C40; and AT&T's DSP32C) and then tested with real-time hardware using real world signals. All of the example programs presented in the text are provided in source code form on the IBM PC floppy disk included with the book.

The text is divided into several sections.

Chapters 1 and 2 cover the basic principles of digital signal processing and C programming. Readers familiar with these topics may wish to skip one or both chapters.

Chapter 3 introduces the basic real-time DSP programming techniques and typical programming environments which are used with DSP microprocessors.

Chapter 4 covers the basic real-time filtering techniques which are the cornerstone of one-dimensional real-time digital signal processing. Finally, several real-time DSP applications are presented in Chapter 5, including speech compression, music signal processing, radar signal processing, and adaptive signal processing techniques.

The floppy disk included with this text contains C language source code for all of the DSP programs discussed in this book. The floppy disk has a high density format and was written by MS-DOS. The appendix and the READ.ME files on the floppy disk provide more information about how to compile and run the C programs. These programs have been tested using Borland's TURBO C (version 3 and greater) as well as Microsoft C (versions 6 and greater) for the IBM PC. Real-time DSP platforms using the Analo g Devices ADSP-21020 and the ADSP-21062, the Texas Instruments TMS320C30, and the AT&T DSP32C have been used extensively to test the real-time performance of the algorithms.