docs: Add Sound Effects documentation. (#753)

* docs: Add Sound Effects documentation.

* docs: Change proposed audio.Effect() to audio.SoundEffect()

* docs: Update the proposed default values for audio.SoundEffect().

* docs: Move the SoundEffects constants from `audio` to `audio.SoundEffect`.

* docs: Remove SoundEffect `preset` constructor parameter, and add `copy()` method.

* docs: Change SoundEffect() `interporlation` parameter to `shape`.

* docs: Remove mentions of SoundEffect presets, add ranges, example to file.

docs/audio.rst

@@ -6,29 +6,57 @@ Audio
 This module allows you play sounds with the micro:bit.
 
 By default sound output will be via the edge connector on pin 0 and the
-:doc:`built-in speaker <speaker>` **V2**. You can connect wired headphones or
+:doc:`built-in speaker <speaker>` (**V2**). You can connect wired headphones or
 a speaker to pin 0 and GND on the edge connector to hear the sounds.
 
 The ``audio`` module can be imported as ``import audio`` or accessed via
 the ``microbit`` module as ``microbit.audio``.
 
+There are three different kinds of audio sources that can be played using the
+:py:meth:`audio.play` function:
+
+1. `Built in sounds <#built-in-sounds-v2>`_ (**V2**),
+   e.g. ``audio.play(Sound.HAPPY)``
+2. `Sound Effects <#sound-effects-v2>`_ (**V2**), a way to create custom sounds
+   by configuring its parameters::
+
+    my_effect = audio.SoundEffect(freq_start=400, freq_end=2500, duration=500)
+    audio.play(my_effect)
+
+3. `Audio Frames <#audioframe>`_, an iterable (like a list or a generator)
+   of Audio Frames, which are lists of 32 samples with values from 0 to 255::
+
+    square_wave = audio.AudioFrame()
+    for i in range(16):
+        square_wave[i] = 0
+        square_wave[i + 16] = 255
+    audio.play([square_wave] * 64)
+
+
 Functions
 =========
 
 .. py:function:: play(source, wait=True, pin=pin0, return_pin=None)
 
-    Play the source to completion.
+    Play the audio source to completion.
 
-    :param source: ``Sound``: The ``microbit`` module contains a list of
-      built-in sounds that your can pass to ``audio.play()``.
+    :param source: There are three types of data that can be used as a source:
+
+        - ``Sound``: The ``microbit`` module contains a list of
+          built-in sounds, e.g. ``audio.play(Sound.TWINKLE)``. A full list can
+          be found in the `Built in sounds <#built-in-sounds-v2>`_ section.
+        - ``SoundEffect``: A sound effect, or an iterable of sound effects,
+          created via the :py:meth:`audio.SoundEffect` class
+        - ``AudioFrame``: An iterable of ``AudioFrame`` instances as described
+          in the `AudioFrame Technical Details <#id2>`_ section
 
-      ``AudioFrame``: The source agrument can also be an iterable
-      of ``AudioFrame`` elements as described below.
     :param wait: If ``wait`` is ``True``, this function will block until the
         source is exhausted.
+
     :param pin: An optional argument to specify the output pin can be used to
       override the default of ``pin0``. If we do not want any sound to play
       we can use ``pin=None``.
+
     :param return_pin: specifies a differential edge connector pin to connect
       to an external speaker instead of ground. This is ignored for the **V2**
       revision.
@@ -41,34 +69,9 @@ Functions
 
     Stops all audio playback.
 
-Classes
-=======
-
-.. py:class::
-    AudioFrame
-
-    An ``AudioFrame`` object is a list of 32 samples each of which is an unsigned byte
-    (whole number between 0 and 255).
-
-    It takes just over 4 ms to play a single frame.
-
-    .. py:function:: copyfrom(other)
-
-        Overwrite the data in this ``AudioFrame`` with the data from another
-        ``AudioFrame`` instance.
-
-        :param other: ``AudioFrame`` instance from which to copy the data.
-
-
-Using audio
-===========
-
-You will need a sound source, as input to the ``play`` function. You can use
-the built-in sounds **V2** from the ``microbit`` module, ``microbit.Sound``, or
-generate your own, like in ``examples/waveforms.py``.
 
 Built-in sounds **V2**
-----------------------
+======================
 
 The built-in sounds can be called using ``audio.play(Sound.NAME)``.
 
@@ -83,8 +86,154 @@ The built-in sounds can be called using ``audio.play(Sound.NAME)``.
 * ``Sound.TWINKLE``
 * ``Sound.YAWN``
 
+Sounds Example
+--------------
+
+::
+
+    from microbit import *
+
+    while True:
+        if button_a.is_pressed() and button_b.is_pressed():
+            # When pressing both buttons only play via the edge connector
+            audio.play(Sound.HELLO, pin=pin0)
+        elif button_a.is_pressed():
+            # On button A play a sound and when it's done show an image
+            audio.play(Sound.HAPPY)
+            display.show(Image.HAPPY)
+        elif button_b.is_pressed():
+            # On button B play a sound and show an image at the same time
+            audio.play(Sound.TWINKLE, wait=False)
+            display.show(Image.BUTTERFLY)
+
+        sleep(500)
+        display.clear()
+
+
+Sound Effects **V2**
+====================
+
+.. py:class::
+    SoundEffect(freq_start=500, freq_end=2500, duration=500, vol_start=255, vol_end=0, wave=WAVE_SQUARE, fx=FX_NONE, shape=SHAPE_LOG)
+
+    An ``SoundEffect`` instance represents a sound effect, composed by a set of
+    parameters configured via the constructor or attributes.
+
+    All the parameters are optional, with default values as shown above, and
+    they can all be modified via attributes of the same name. For example, we
+    can first create an effect ``my_effect = SoundEffect(duration=1000)``,
+    and then change its attributes ``my_effect.duration = 500``.
+
+    :param freq_start: Start frequency in Hertz (Hz), default: ``500``
+    :param freq_end: End frequency in Hertz (Hz), default: ``2500``
+    :param duration: Duration of the sound (ms), default: ``500``
+    :param vol_start: Start volume value, range 0-255, default: ``255``
+    :param vol_end: End volume value, range 0-255, default: ``0``
+    :param wave: Type of wave shape, one of these values: ``WAVE_SINE``,
+        ``WAVE_SAWTOOTH``, ``WAVE_TRIANGLE``, ``WAVE_SQUARE``,
+        ``WAVE_NOISE`` (randomly generated noise). Default: ``WAVE_SQUARE``
+    :param fx: Effect to add on the sound, one of the following values:
+        ``FX_TREMOLO``, ``FX_VIBRATO``, ``FX_WARBLE``, or ``FX_NONE``.
+        Default: ``FX_NONE``
+    :param shape: The type of the interpolation curve between the start and end
+        frequencies, different wave shapes have different rates of change
+        in frequency. One of the following values: ``SHAPE_LINEAR``,
+        ``SHAPE_CURVE``, ``SHAPE_LOG``. Default: ``SHAPE_LOG``
+
+    .. py:function:: copy()
+
+        :returns: A copy of the SoundEffect.
+
+    .. py:attribute:: freq_start
+
+        Start frequency in Hertz (Hz), a number between ``0`` and ``9999``.
+
+    .. py:attribute:: freq_end
+
+        End frequency in Hertz (Hz), a number between ``0`` and ``9999```.
+
+    .. py:attribute:: duration
+
+        Duration of the sound in milliseconds, a number between ``0`` and
+        ``9999``.
+
+    .. py:attribute:: vol_start
+
+        Start volume value, a number between ``0`` and ``255``.
+
+    .. py:attribute:: vol_end
+
+        End volume value, a number between ``0`` and ``255``.
+
+    .. py:attribute:: wave
+
+        Type of wave shape, one of these values: ``WAVE_SINE``,
+        ``WAVE_SAWTOOTH``, ``WAVE_TRIANGLE``, ``WAVE_SQUARE``,
+        ``WAVE_NOISE`` (randomly generated noise).
+
+    .. py:attribute:: fx
+
+        Effect to add on the sound, one of the following values:
+        ``FX_TREMOLO``, ``FX_VIBRATO``, ``FX_WARBLE``, or ``None``.
+
+    .. py:attribute:: shape
+
+        The type of interpolation curve between the start and end
+        frequencies, different wave shapes have different rates of change
+        in frequency. One of the following values: ``SHAPE_LINEAR``,
+        ``SHAPE_CURVE``, ``SHAPE_LOG``.
+
+The arguments used to create any Sound Effect,
+can be inspected by looking at each of the SoundEffect instance attributes,
+or by converting the instance into a string (which can be done via ``str()``
+function, or by using a function that does the conversion automatically like
+``print()``).
+
+For example, with the :doc:`REPL </devguide/repl>` you can inspect the
+default SoundEffects::
+
+    >>> print(audio.SoundEffect())
+    SoundEffect(freq_start=500, freq_end=2500, duration=500, vol_start=255, vol_end=0, wave=WAVE_SQUARE, fx=FX_NONE, shape=SHAPE_LOG)
+
+This format is "human readable", which means it is easy for us to read,
+and it looks very similar to the code needed to create that SoundEffect,
+but it's not quite right. The ``repr()`` function can be used to create a
+string of Python code that can be stored or transferred
+(you could transmit sounds via micro:bit radio!) and be executed with the
+``eval()`` function::
+
+    >>> from audio import SoundEffect
+    >>> sound_code = repr(SoundEffect())
+    >>> print(sound_code)
+    SoundEffect(500, 2500, 500, 255, 0, 3, 0, 18)
+    >>> eval("audio.play({})".format(sound_code))
+
+Sound Effects Example
+---------------------
+
+.. include:: ../examples/soundeffects.py
+    :code: python
+
+AudioFrame
+==========
+
+.. py:class::
+    AudioFrame
+
+    An ``AudioFrame`` object is a list of 32 samples each of which is an unsigned byte
+    (whole number between 0 and 255).
+
+    It takes just over 4 ms to play a single frame.
+
+    .. py:function:: copyfrom(other)
+
+        Overwrite the data in this ``AudioFrame`` with the data from another
+        ``AudioFrame`` instance.
+
+        :param other: ``AudioFrame`` instance from which to copy the data.
+
 Technical Details
-=================
+-----------------
 
 .. note::
     You don't need to understand this section to use the ``audio`` module.
@@ -104,11 +253,11 @@ samples. When reading reaches the start or the mid-point of the buffer, it
 triggers a callback to fetch the next ``AudioFrame`` which is then copied into
 the buffer. This means that a sound source has under 4ms to compute the next
 ``AudioFrame``, and for reliable operation needs to take less 2ms (which is
-32000 cycles, so should be plenty).
+32000 cycles in micro:bit V1 or 128000 in V2, so should be plenty).
 
 
-Example
-=======
+AudioFrame Example
+------------------
 
 .. include:: ../examples/waveforms.py
     :code: python

examples/soundeffects.py

@@ -0,0 +1,53 @@
+from microbit import *
+
+# Play the default Sound Effect
+audio.play(audio.SoundEffect())
+
+# Create a new Sound Effect and immediately play it
+audio.play(audio.SoundEffect(
+    freq_start=400,
+    freq_end=2000,
+    duration=500,
+    vol_start=100,
+    vol_end=255,
+    wave=audio.SoundEffect.WAVE_TRIANGLE,
+    fx=audio.SoundEffect.FX_VIBRATO,
+    shape=audio.SoundEffect.SHAPE_LOG
+))
+
+# Play a Sound Effect instance, modify an attribute, and play it again
+my_effect = audio.SoundEffect(
+    freq_start=400,
+    freq_end=2000,
+)
+audio.play(my_effect)
+my_effect.duration = 1000
+audio.play(my_effect)
+
+# You can also create a new effect based on an existing one, and modify
+# any of its characteristics via arguments
+my_modified_effect = my_effect.copy()
+my_modified_effect.wave = audio.SoundEffect.WAVE_NOISE
+audio.play(my_modified_effect)
+
+# Use sensor data to modify and play an existing Sound Effect instance
+my_effect.duration = 600
+while True:
+    # int() might be temporarily neededhttps://github.com/microbit-foundation/micropython-microbit-v2/issues/121
+    my_effect.freq_start = int(scale(accelerometer.get_x(), from_=(-2000, 2000), to=(0, 9999)))
+    my_effect.freq_end = int(scale(accelerometer.get_y(), from_=(-2000, 2000), to=(0, 9999)))
+    audio.play(my_effect)
+
+    if button_a.is_pressed():
+        # Button A silences the micro:bit
+        speaker.off()
+        display.show(Image("09090:00000:00900:09990:00900"))
+        sleep(500)
+    elif button_b.is_pressed():
+        # On button B re-enable speaker & play an effect while showing an image
+        speaker.on()
+        audio.play(audio.SoundEffect(), wait=False)
+        display.show(Image.MUSIC_QUAVER)
+        sleep(500)
+
+    sleep(150)