AN2400 Datasheet, PDF (1/23 Pages) STMicroelectronics – Audio player evaluation board based on ST7Lite

AN2400
Application note
Audio player evaluation board
based on ST7Lite
Introduction
This application note demonstrates how to add audio playback to any application using a
general-purpose ST7 microcontroller. To demonstrate this feature, an evaluation board,
source code in C, schematics, and layout are available.
The Audio player evaluation board reconstructs audio signals through the PWM of a
ST7FLITES2 microcontroller. Serial Flash is used to store the audio data in a binary file
format. To store this audio data in the Flash, the sound files need to be in .wav format so that
can be converted into .bin file format with the help of the PC GUI available with this package.
Once the data is stored, the microcontroller reads it through an SPI interface and generates
the sound using the PWM feature. A sixth order low pass filter removes any unwanted high
frequency components from the signal before passing it through a speaker.
The key features of the Audio player evaluation board are as follows:
■ 1% calibrated on-chip RC oscillator. The used microcontroller, ST7FLITES2, contains an
internal RC oscillator with an accuracy of 1% for a given device. It can be calibrated to
obtain a frequency required for the application. There is therefore no need for any external
oscillator.
■ LVD (brown-out) on chip. The purpose of the Low Voltage Detector (LVD) is to ensure that
the ST7 always functions in its safe area. No external reset circuit is required.
■ Small footprint solution.
■ Low power operation. Reduces battery/power supply cost (through extended battery life).
■ Supports lower density serial Flash if fewer messages needed.
■ Order of filter can be reduced to cut cost even more.
November 2006
Rev 1
1/23
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