This application note describes a simple and easy-to-use solution to help design and develop products with an audio output, for example, toys, white goods, washing machines, and alarms. Audio data generally require the storage of a lot of memory. However, the memory space needed to preserve such data can be reduced by compressing the audio data via a specified compression method. Processing these data is a complex task requiring powerful microcontrollers such as DSP or audio chip. Usually, 8-bit microcontrolles do not offer either a large memory or a high computing performance. The software solution offered in this application note reconstructs audio signals from compressed samples. A simple audio codec based on an adaptive differential pulse coded modulation (ADPCM) algorithm is used and advantage is taken of the advanced STM8S core with its 3-staged pipeline and 16 or 24 MIPS peak performance. The digital samples are usually converted to an analog signal by some external or onchip digital-to-analog converter (DAC). There are a lot of applications where the high fidelity audio output is not a priority and/or the use of an external DAC is not a suitable cost- effective solution for 8-bit microcontrollers. To reduce costs and to offer a good quality audio, an ideal solution is to generate an audio signal using pulse width modulation (PWM).