import machine
import time

sensor_trig = machine.Pin(5, machine.Pin.OUT)
sensor_echo = machine.Pin(18, machine.Pin.IN)
buzzer = machine.PWM(machine.Pin(2))
buzzer.duty(0) 
boton_encendido = machine.Pin(4, machine.Pin.IN, machine.Pin.PULL_UP)

ultimo_valor_distancia = -1
sistema_activo = True

def medir_distancia():
    sensor_trig.value(0)
    time.sleep_us(5)
    sensor_trig.value(1)
    time.sleep_us(10)
    sensor_trig.value(0)
    duracion = machine.time_pulse_us(sensor_echo, 1, 30000)
    distancia = (duracion / 2) / 29.1
    return int(distancia)

while True:
    if boton_encendido.value() == 0:
        sistema_activo = not sistema_activo
        time.sleep(0.5) 
        
    if sistema_activo:
        distancia = medir_distancia()
        if 40 < distancia < 60:
            buzzer.freq(1000); buzzer.duty(512); time.sleep(0.5); buzzer.duty(0); time.sleep(0.5)
        elif 20 <= distancia <= 40:
            buzzer.freq(1500); buzzer.duty(512); time.sleep(0.2); buzzer.duty(0); time.sleep(0.2)
        elif 0 < distancia < 20:
            buzzer.freq(2000); buzzer.duty(512)
        else:
            buzzer.duty(0)
        
    time.sleep(0.1)