from machine import Pin, PWM
from time import sleep

# Create PWM object on LED pin
led = PWM(Pin(5))

# Set PWM frequency
led.freq(1000)   # 1000 Hz

while True:
    # Increase brightness
    for duty in range(0, 1024, 32):
        print (f"Duty =",duty)
        led.duty(duty)
        sleep(0.5)

    # Decrease brightness
    for duty in range(1023, -1, -32):
        led.duty(duty)
        print (f"Duty =",duty)
        sleep(0.5)