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 pin.

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.

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

instance:detach()

Detach the servo and free all resources used by the servo.

Arguments: none.

Returns: nothing, or an exception.

-- Detach the servo
s:detach()

Operation functions

instance:write(value)

Write a value to a servo instance, controlling the servo movement according to the type of servo:

• For standard servos: the value is the servo's absolute position expressed in degrees. Typically, the value goes from 0º to 180º. In this case writing a new value, moves the servo from it's current position to a new position, and then stops.

• For continuous rotation servos: the value is expressed also in degrees, being 0º full-speed counter clock wise, 180º full-speed clock wise, and 90º being no movement. In this case, writing a new value, changes the servo rotation direction, or the rotation speed.

Arguments:

• value: the value to write, expressed in degrees.

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)