from machine import Pin, PWM
from time import sleep

# Wait for USB to become ready
sleep(0.1)

# Setup PWM on GP15
led = PWM(Pin(15))
led.freq(1000)   # 1 kHz PWM frequency (good for LEDs)
#-----------------main--------------------
while True:
    # Fade IN (0 -> 100%)
    for duty in range(0, 65536, 1000):
        led.duty_u16(duty)
        sleep(0.05)

    # Fade OUT (100% -> 0)
    for duty in range(65535, -1, -1000):
        led.duty_u16(duty)
        sleep(0.05)