AIC111pdf(Efficient Resamplin

The AIC111 is an ultralow-power, fixed sample rate, sigma-delta codec with a sample rate of
40 kHz and a usable bandwidth of 10 kHz. Typically, most applications process data at
sample rates of 8 kHz, 16 kHz, and 20 kHz. This requires that the DSP or microprocessor
connected to the AIC111 decimate the incoming data from 40 kHz down to the required
sampling frequency, and interpolate the data back up to 40 kHz. This document outlines
several methods and examples of resampling incoming data from  the AIC111 at 40 kHz to the
required processing sampling rate between 8 kHz and 20 kHz using decimation and
interpolation techniques on a digital signal processor (DSP) or a microprocessor. In many
situations, it may also be possible to exploit characteristics of supplementary signal
processing stages in the system to relax filter specifications or even remove certain
resampling stages for additional savings in computation. The document also provides some
suggestions on ways to exploit these characteristics. The document also addresses how to
use the H-bridge output on the AIC111 to drive speakers with varying impedance and
bandwidth. Example routines have been developed specifically for use with the AIC111 audio
codec and the Texas Instruments (TI) TMS320C54x™ (C54x™) DSP for speech/audio
applications.