A survey of techniques to add audio module to embedded systems

In many embedded application systems, it is desirable to incorporate an audio module/functionality to the system such that the system can utter meaningful audio messages in a controlled manner. An audio system in the embedded setting may consist of memory module, Compression/Decompression (CODEC) module, Digital-to-Analog Converter (DAC) module, filter module, power amplifier module; and also (if the function of voice recording is needed) the signal conditioning module, Automatic Gain Control (AGC), and Analog-to-Digital Conversion (ADC) module. Depending on the different demands of various application scenarios, different techniques can be used to implement the audio module. If no audio signal processing is required, the approach of using a dedicated, off-the-shelf, voice chip is preferable. In other cases, individual circuits would have to be built for some or all of the peripheral modules required in an audio system. The major advantage of this approach is increased level of flexibility; while the immediate disadvantage is rising development cost and a higher level of system complexity. In this paper, we first outline the general operation principle of a typical audio system module; then, a sample implementation that uses a dedicated voice chip is introduced and explained in great detail so that it can be used by students and application engineers as a functional reference design.