"""

Nonblocking Buzzer implementation for Micropython

The method check() takes very little time in the main loop

1. Initialize de `NonBlocking_Buzzer` object just with the buzzer pin.

2. Start the buzzer with the list of frequencies to play, timing information (note duration, delay between notes and delay between repetitions) and the number of repetitions.

3. Use the `check()` method in the main loop so that the NonBlocking_Buzzer can update its state.

jornamon 2022

"""

import time

from machine import PWM, Pin

class NonBlocking_Buzzer():

def __init__(self, pin):

self._buzzer = PWM(pin, freq=2048, duty=0)

self._state = 'STOPPED'

self._duty_on = 512 # 0 to 1023

def start(self, notes, delay_note=50, delay_inter=25, delay_rep=150, reps=1, mute=False):

if mute:

return

temp_notes = []

for r in range(reps):

for n in notes:

temp_notes.extend([n,0])

temp_notes.append(0)

self._freq = tuple(temp_notes)

del temp_notes

self._duty = ((self._duty_on,0)*len(notes)+(0,))*reps

self._delay = ((delay_note,delay_inter)*len(notes)+(delay_rep,))*reps

self._steps = len(self._delay)

self._state = 'WORKING'

self._buzzer.freq(self._freq[0])

self._buzzer.duty(self._duty[0])

self._next_time = time.ticks_add(time.ticks_ms(),self._delay[0])

self._next_step = 1

def check(self):

if self._state == 'STOPPED':

return

if time.ticks_ms() < self._next_time:

return

if self._duty[self._next_step] != 0:

self._buzzer.freq(self._freq[self._next_step])

self._buzzer.duty(self._duty[self._next_step])

self._next_time = time.ticks_add(time.ticks_ms(),self._delay[self._next_step])

self._next_step += 1

if self._next_step == self._steps - 1:

self._state = 'STOPPED'

def stop(self):

self._state = 'STOPPED'

self._buzzer.duty(0)