from machine import Pin , PWM
from time import sleep

led = PWM(Pin(5) , 5000)

while True:
    for duty_cycle in range(0, 1024 , 10):
        led.duty(duty_cycle)
        sleep(0.03)
    for duty_cycle in range(1023, -1, -10):
        led.duty(duty_cycle)
        sleep(0.03)
#    led.duty(1000)
#    sleep(0.2