from hcsr04 import HCSR04
from machine import Pin
ultrasonic =HCSR04(trigger_pin = 13, echo_pin = 12)
from time import sleep
buzzer = Pin (16, Pin.OUT)

while True:
    jarak = ultrasonic.distance_cm()
    print ('jarak: ', jarak, "cm")
    sleep(0.1)

    if (jarak < 20):
        buzzer.on()
        sleep(0.5)
        buzzer.off
        sleep(0.5)
    else:
        buzzer.off()