Digital Signal Processing and Applications with the OMAP-L138 eXperimenter

Chapter 2

Analog Input and Output with the OMAP-L138 eXperimenter

• Analog input and output using the on-board AIC3106 stereo codec
• Programming examples using C code

2.1 INTRODUCTION

A basic DSP system, suitable for processing audio frequency signals, comprises a digital signal processor and analog interfaces, as shown in Figure 2.1. The eXper-imenter provides just such a system, using the C6748 floating-point processor core contained within an OMAP-L138 device and a TLV320AIC3106 (AIC3106) codec [1]. The term codec refers to the coding of analog waveforms as digital signals and the decoding of digital signals as analog waveforms. The AIC3106 codec performs both the analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC) functions shown in Figure 2.1.

The AIC3106 communicates with the C6748 via multichannel audio serial port (McASP) and I2C interfaces and these are also made available on the eXperimenter board via an audio expansion connector, allowing the addition of further codecs. The programming examples in this book use only the eXperimenter's on-board AIC3106 codec.

Figure 2.1 Basic digital signal processing system.

2.2.1 Sampling, Reconstruction, and Aliasing

Within digital signal processors, signals are represented as sequences of discrete samples and whenever signals are sampled, the possibility of aliasing arises. Later in this chapter, the phenomenon ...