from machine import Pin, PWM
from time import sleep

LED_PIN = 15
BTN_PIN = 16
x = 65535

led_pwm = PWM(Pin(LED_PIN))
led_pwm.freq(1000)  #1kHz


led_pwm.duty_u16(x)

while True:
    while x > 10:
        x -= 10
        led_pwm.duty_u16(x)
   
    while x < 65435:
        x += 10
        led_pwm.duty_u16(x)