from machine import Pin, PWM
from time import ticks_ms, sleep_ms

# C4 = 261 Hz, E4 = 329 Hz, G4 = 392 Hz, A4 = 440 Hz
buzzer = PWM(Pin(13))
start_time = ticks_ms()

while True:
    elapsed_time = ticks_ms() - start_time

    if elapsed_time < 2000:      # C4
        buzzer.duty_u16(32768)
        buzzer.freq(261)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)

    elif elapsed_time < 4000:    # E4
        buzzer.duty_u16(32768)
        buzzer.freq(329)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)

    elif elapsed_time < 6000:    # G4
        buzzer.duty_u16(32768)
        buzzer.freq(392)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)

    elif elapsed_time < 8000:    # A4
        buzzer.duty_u16(32768)
        buzzer.freq(440)
        sleep_ms(200)
        buzzer.duty_u16(0)
        sleep_ms(100)

    else:
        buzzer.duty_u16(0)
        break