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Fig. 3.2: Audio Project Example - Internet Connected Radio Player
3.1.3 Typical Project
When looking for better audio quality and more interfacing options we would use an external I2S codec to do all the
analog input and output signal processing. The codec chip, depending on type, may provide additional functionality
like audio input signal preamplifier, headphone output amplifier, multiple analog input and outputs, sound effects, etc.
The
is considered as the industry standard for interfacing with audio codec chips, or in general for a high speed,
continuous transfer of the audio data. To optimize performance of audio data processing additional memory may be
required. For such cases consider using
that provides 4 MB PSRAM on a single module together
with the ESP32 chip.
The ESP-ADF is designed primarily to support projects with a codec chip. The
board is an example of
such a project. The software interfacing with the board is done by Audio HAL and a driver. The codec chip used on
the ESP32 LyraT is
. Boards with a different codec chip may be supported by providing a different driver.
3.2 Design Considerations
Depending on the audio data format, that may be lossless, lossy or compressed, e.g. WAV, MP3 or FLAC and the
quality expressed in sampling rate and bitrate, the project will require different resources: memory, storage space,
input / output throughput and the processing power. The resources will also depend on the project type and features
discussed in
This section describes capacity and performance of ESP32 system resources that should be considered when designing
an audio project to meet required data format, audio quality and functionality.
3.2.1 Memory
The spare internal Data-RAM is about 290kB with “hello_world” example. For audio system this may be insufficient,
and therefore the ESP32 incorporates the ability to use up to 4MB of external SPI RAM (i.e. PSRAM) memory. The
3.2. Design Considerations
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