AN706-00040-2v0-E
67
(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 MP3 file,
quit the file system and operation shifts to initialization status.
③
If the USB memory is connected, play/stop switch press down detection and
touch panel touch detection are executed.
④
If the play/stop switch is detected to have been pressed down, or if not detected,
but an area of the touch panel is detected to have been touched, playback is
stopped, the MPA file is closed, all JPEF filed are read from the USB memory, that
images for selection are displayed and operation shifts to audio data playback
stopped status.
⑤
Verify vacancy of input buffer.
⑥
If there is sufficient vacancy, the MP3 file is read from the USB memory and
copied in the input buffer.
⑦
One frame of the input buffer is decoded and stored in the RAW buffer.
⑧
When 1 frame 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 49.
