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