from machine import Pin,PWM
from time import sleep

ledPin=PWM(Pin(26))
ledPin.freq(1000)
ledPin.duty_u16(0)

duty=0;
diff=1000
while True:
    if duty>65536 :
        duty=65536
        diff*=-1
        sleep(0.1)
    if duty<0:
        duty=0
        diff*=-1
        sleep(0.1)
    print(duty)
    ledPin.duty_u16(duty)
    duty+=diff
    
    sleep(0.01)