Most of you already seen simple audio output trough the micro controller PWM channel, this project is very simple, and gives you a set of PC programs which are useful to convert plain text to audio stream. The firmware is basically a simple interface between the audio amplifier and PC, the data stream is received by the controller trough the serial port with 8kHz refresh rate and written directly to the PWM registers. The quality is poor but this device isn’t intended for hi-fi applications, although it is well suited for speech playback.
This can be a great alternative for LCD displays, since for mono audio you need only 1 output pin, you can seriously reduce the pin count of your application, the only disadvantage is the large memory needed to store the audio stream, luckily the SD cards are getting cheaper every day.
The 8kHz refresh rate shouldn’t pose any problem, even an 8 bit micro controller running on 8MHz clock can easily manage the SD card reading and PWM refresh, without major system overhead.