from machine import Pin,PWM
import time

pwm = PWM(Pin(14))
pwm.freq(1000)

while True:
    pwm.duty_u16(0)
    time.sleep(1)

    pwm.duty_u16(256)
    time.sleep(1)

    pwm.duty_u16(512)
    time.sleep(1)

    pwm.duty_u16(1024)
    time.sleep(1)

    pwm.duty_u16(20000)
    time.sleep(1)

    pwm.duty_u16(50000)
    time.sleep(1)