DocID024112 Rev 1

13/26

AN4229

Package content and description

25

While simple examples features are:

•

Only one codec (amongst G.711, G.726, IMA-ADPCM and Speex) is supported in each

example

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Minimalist user interface

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Play and record on internal flash memory

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Simple commands using tamper (play/stop) and key (record/stop) push buttons

2.2

Audio API description

There are multiple abstraction layers for the audio components:

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Decoders and mass storage operation management

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Output interface (codec, I2S,DMA…) management, independently from FatFS

operations: it allows managing all output interface without caring about hardware layer

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Input Interface (ADC, MEMS PDM, microphones…): it allows managing all input

interfaces without caring about hardware layer.

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High abstraction layer (AudioPlayer_xxx and AudioRecorder_xxx)

All decoding/encoding operations are called by the abstraction layer interfaces (AudioPlayer

and AudioRecorder) as well as the read/write functions using FatFS library or equivalent for

read/write operations from internal STM32 flash memory. So when the application calls this

level of API, it doesn't need to call decoders/encoders or mass storage

open/write/read/close functions. Figure 5 and Figure 6 explain the structure of the high layer

for the audio player and recorder respectively.