99 lines
3.3 KiB
ReStructuredText
99 lines
3.3 KiB
ReStructuredText
The AMP audio skin
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==================
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Soldering and using the AMP audio skin.
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.. image:: img/skin_amp_1.jpg
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:alt: AMP skin
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:width: 250px
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.. image:: img/skin_amp_2.jpg
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:alt: AMP skin
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:width: 250px
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The following video shows how to solder the headers, microphone and speaker onto the AMP skin.
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.. raw:: html
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<iframe style="margin-left:3em;" width="560" height="315" src="http://www.youtube.com/embed/fjB1DuZRveo?rel=0" frameborder="0" allowfullscreen></iframe>
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For circuit schematics and datasheets for the components on the skin see :ref:`hardware_index`.
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Example code
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------------
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The AMP skin has a speaker which is connected to ``DAC(1)`` via a small
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power amplifier. The volume of the amplifier is controlled by a digital
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potentiometer, which is an I2C device with address 46 on the ``IC2(1)`` bus.
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To set the volume, define the following function::
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import pyb
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def volume(val):
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pyb.I2C(1, pyb.I2C.MASTER).mem_write(val, 46, 0)
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Then you can do::
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>>> volume(0) # minimum volume
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>>> volume(127) # maximum volume
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To play a sound, use the ``write_timed`` method of the ``DAC`` object.
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For example::
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import math
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from pyb import DAC
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# create a buffer containing a sine-wave
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buf = bytearray(100)
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for i in range(len(buf)):
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buf[i] = 128 + int(127 * math.sin(2 * math.pi * i / len(buf)))
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# output the sine-wave at 400Hz
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dac = DAC(1)
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dac.write_timed(buf, 400 * len(buf), mode=DAC.CIRCULAR)
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You can also play WAV files using the Python ``wave`` module. You can get
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the wave module `here <http://micropython.org/resources/examples/wave.py>`__ and you will also need
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the chunk module available `here <http://micropython.org/resources/examples/chunk.py>`__. Put these
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on your pyboard (either on the flash or the SD card in the top-level directory). You will need an
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8-bit WAV file to play, such as `this one <http://micropython.org/resources/examples/test.wav>`_,
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or to convert any file you have with the command::
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avconv -i original.wav -ar 22050 -codec pcm_u8 test.wav
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Then you can do::
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>>> import wave
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>>> from pyb import DAC
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>>> dac = DAC(1)
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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. 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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