import time
from machine import Pin, time_pulse_us
TRIG_PIN = 5
ECHO_PIN = 18
BUZZER_PIN = 4
trig = Pin(TRIG_PIN, Pin.OUT)
echo = Pin(ECHO_PIN, Pin.IN)
buzzer = Pin(BUZZER_PIN, Pin.OUT)
def get_distance_cm():
  trig.value(0)
  time.sleep_us(2)
  trig.value(1)
  time.sleep_us(10)
  trig.value(0)
  duration = time_pulse_us(echo, 1, 30000) # 30ms timeout ~ 5m max range
  if duration < 0:
    return None
  return (duration * 0.0343) / 2 # speed of sound -> cm
print("Ultrasonic obstacle alert system started.")
while True:
  distance = get_distance_cm()
  if distance is None:
    print("No echo received (out of range).")
    buzzer.value(0)
  else:
    print("Distance: {:.1f} cm".format(distance))
    if distance < 15:
      buzzer.value(1)
      print("BUZZER ON - Obstacle too close!")
    else:
      buzzer.value(0)
      print("BUZZER OFF - Clear path")
print("------------------------")
time.sleep(1)