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(2) The application operation flow with audio data playback in progress is as follows.
①
USB MSC device connection/disconnection judgment is executed in the main
loop.
②
If the USB memory has been removed, stop playback, close the opened AAC file,
quit the file system and operation shifts to initialization status.
③
If the USB memory is connected, play/stop button press-down detection is
executed.
④
If the play/stop button is detected to have been pressed down, playback stops,
the AAC file is closed, and operation shifts to audio data playback stop status.
⑤
Verify vacancy of input buffer.
⑥
If there is sufficient vacancy, the AAC file is read from the USB memory and
copied in the input buffer.
⑦
One elementary stream of the input buffer is decoded and stored in the RAW
buffer.
⑧
When 1 elementary stream had been decoded, the RAW buffer is up-sampled
and buried in the output buffer.
⑨
With DMA ch2 interrupt, data is sent from the output buffer to I
2
S in sequence.
This operation is shown in Figure 51.
