from hcsr04 import HCSR04
import machine
import time

buzzer=Pin(1,Pin.OUT)
sensor = HCSR04(trigger_pin=3,echo_pin=2,echo_timeout_us=1000000)

while True:
 distance = sensor.distance_cm() 
 print(distance,' cm')
 time.sleep_ms(100)
 if (distance<4):
   buzzer.value(1) # buzzer sounds
 else:
   buzzer.value(0) #buzzer stops