SOUND module

About this

This module contains functions to generate audible tones, attaching a piezo buzzer or a speaker to an output GPIO. The module can be used in two ways:

• Raw notation, in which tones are described in terms of their frequency and duration.

• Musical notation, in which tones are described in terms of the musical note, note duration, octave, time signature, etc ...

Tone generator

Tones are synthesized by the module using a tone generator:

Generator	Id	Description
PWM	sound.PWM	The tone is synthesized by a PWM hardware module, which generates a square wave with a 50% duty cycle.
DAC	sound.DAC	The tone is synthesized by an I2S / DAC hardware module, which generates a sine wave at a 38 KHz sampling rate.

Configuration funcions

instance = sound.attach(tone_generator, pin)

Attach a tone generator to a piezo buzzer or a speaker.

Arguments:

• tone_generator: tone generator used to synthesize the tone.
• pin: GPIO where the piezo buzzer or the speaker is attached.

Returns: a sound instance, or an exception. You must store this instance into a variable for further operations with it.

instance:detach()

Detach the tone generator and free all resources used.

Arguments: none.

Returns: nothing, or an exception.

Operation functions

instance:playnote(note, octave)

Play a musical note on the desired octave.

Arguments:

• note: a formatted string describing the musical note to play and it's duration.

  • note name: the name of the note using the English naming convention.

    English	German	Latin
    A	A	La
    B	H	Si
    C	C	Do
    D	D	Re
    E	E	Mi
    F	F	Fa
    G	G	Sol

    Notes in English naming convention, and their correspondence to other naming conventions.

  • accidental (optional): can be either # to raise the note by a semitone or b to lower the note by the same amount.

  • duration:

    Duration	English	USA
    1	Semibreve	Whole note
    2	Minim	Half note
    4	Crotchet	Quarter note
    8	Quaver	Eighth note
    16	Semiquaver	Sixteenth note	♪
    32	Demisemiquaver	Thirty-second note	♫
    64	Hemidemisemiquaver	Sixty-fourth note	♬

• octave: the octave

Returns: nothing, or an exception.

-- Attach the servo to GPIO26
s = servo.attach(pio.GPIO26)

-- Move an standard servo to the 45º position
s:write(45)

-- Attach the servo to GPIO26
s = servo.attach(pio.GPIO26)

-- Move a continuous rotation servo clock wise at full-speed
s:write(180)