import time # librería delay
import board # librería placa
import pulseio # librería PWM

led = pulseio.PWMOut(board.D13, frequency=50, duty_cycle=0) # Seteo de pin y frecuencia

while True:
    for i in range(100):
        if i < 50:
            led.duty_cycle = int(i * 2 * 65535 / 100)
        else:
            led.duty_cycle = 65535 - int((i - 50) * 2 * 65535 / 100)
        time.sleep(0.01)