from machine import PWM, Pin 
pwm = PWM(Pin (18))
pwm.freq(500) #t=2ms
continuar = True

while continuar: 
    a = input('Digite un valor de 0 a 100:  ')
    if a =='z': 
        continuar = False
    else:
        pwm.duty_u16(int(a)*100)
pwm.deinit()
print('Fin del programa')