from machine import Pin,PWM
from time import sleep

led = PWM(Pin(2))
led.freq(1000)  


while True: 
    for duty in range (0, 65353, 1024):
        led.duty_u16(duty)
        sleep(0.01)

    for duty in range (65353, 0, -1024):
        led.duty_u16(duty)
        sleep(0.01)