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.. _3.1.3_py:

3.1.3 Audio Module
=====================

Introduction
-----------------

In this project, let's make a DIY stereo with an audio power amplifier module, 8ohm/2w speakers and a 3.5mm Audio cable.


Required Components
------------------------------

In this project, we need the following components. 

.. image:: ../img/audio2.png
  :width: 700
  :align: center

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Raphael Kit
        - 337
        - |link_Raphael_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 30 20
    :header-rows: 1

    *   - COMPONENT INTRODUCTION
        - PURCHASE LINK

    *   - :ref:`cpn_gpio_extension_board`
        - |link_gpio_board_buy|
    *   - :ref:`cpn_breadboard`
        - |link_breadboard_buy|
    *   - :ref:`cpn_audio_speaker`
        - \-

Experimental Procedures
------------------------------

**Step 1:** Build the circuit.

.. image:: ../img/4.1.4fritzing.png
    :width: 800
    :align: center

After building the circuit according to the above diagram, then plug the audio cable into the Raspberry Pi’s 3.5mm audio jack.

.. image:: ../img/audio4.png
    :width: 400
    :align: center

**Step 2:** Get into the folder of the code.

.. raw:: html

   <run></run>

.. code-block::

    cd ~/raphael-kit/python/

**Step 3:** Run.

.. raw:: html

   <run></run>

.. code-block::

    python3 3.1.3_AudioModule.py

After the code runs, you can enjoy the music.

.. note::

    If your speaker have no sound, it may be because the Raspberry Pi has selected the wrong audio output (The default is HDMI), you need to :ref:`change_audio_output` to Headphones.

    If you feel that the volume of the speakers is too low, you can :ref:`adjust_volume`.

**Code**

.. note::
    You can **Modify/Reset/Copy/Run/Stop** the code below. But before that, you need to go to  source code path like ``raphael-kit/python``. After modifying the code, you can run it directly to see the effect.

.. raw:: html

    <run></run>

.. code-block:: python

    from pygame import mixer
    import os
    user = os.getlogin()
    user_home = os.path.expanduser(f'~{user}')

    mixer.init()
    
    def main():
        mixer.music.load(f'{user_home}/raphael-kit/music/my_music.mp3')
        mixer.music.set_volume(0.7)
        mixer.music.play()
        while True:
            pass# Don't do anything.
    
    def destroy():
        mixer.music.stop()
    
    if __name__ == '__main__':
        try:
            main()
        except KeyboardInterrupt:
            destroy()

**Code Explanation**

.. code-block:: python

    from pygame import mixer

    mixer.init()

Import the ``mixer`` method in the ``pygame`` library and initialize the method.

.. code-block:: python

    mixer.music.load(f'{user_home}/raphael-kit/music/my_music.mp3')
    mixer.music.set_volume(0.7)
    mixer.music.play()


This code reads the ``my_music.mp3`` file in the ``~/raphael-kit/music`` directory and sets the volume to 0.7(The range is 0~1). 
The Raspberry Pi will start playing audio When ``mixer.music.play()`` is called.

.. note::
    
    You can also upload other music files to your Raspberry Pi. For a detailed tutorial, please refer to: :ref:`filezilla`

.. code-block:: python

    mixer.music.stop()

Calling ``mixer.music.stop()`` will stop playing audio.
In addition, you can also pause with ``mixer.music.pause()`` and continue with ``mixer.music.unpause()``.

**Phenomenon Picture**
------------------------

.. image:: ../img/3.1.3audio.JPG
   :align: center