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docs/pyboard/tutorial/amp_skin: Add example for playing large WAV files.
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‎docs/pyboard/tutorial/amp_skin.rst‎

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@@ -69,4 +69,30 @@ Then you can do::
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>>> f = wave.open('test.wav')
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>>> dac.write_timed(f.readframes(f.getnframes()), f.getframerate())
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This should play the WAV file.
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This should play the WAV file. Note that this will read the whole file into RAM
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so it has to be small enough to fit in it.
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To play larger wave files you will have to use the micro-SD card to store it.
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Also the file must be read and sent to the DAC in small chunks that will fit
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the RAM limit of the microcontroller. Here is an example function that can
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play 8-bit wave files with up to 16kHz sampling::
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import wave
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from pyb import DAC
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from pyb import delay
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dac = DAC(1)
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def play(filename):
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f = wave.open(filename, 'r')
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total_frames = f.getnframes()
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framerate = f.getframerate()
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for position in range(0, total_frames, framerate):
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f.setpos(position)
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dac.write_timed(f.readframes(framerate), framerate)
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delay(1000)
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This function reads one second worth of data and sends it to DAC. It then waits
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one second and moves the file cursor to the new position to read the next second
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of data in the next iteration of the for-loop. It plays one second of audio at
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a time every one second.

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