from machine import *
import utime

trigger_pin=Pin(4,Pin.OUT)
echo_Pin=Pin(5,Pin.OUT)
buzzer_pin=Pin(1,Pin.OUT)
pwm=PWM(buzzer_pin)
def measure_distance():
    trigger_pin.on()
    utime.sleep_us(10)
    trigger_pin.off()

    while echo_Pin.value()==0:
        pulse_start=utime.ticks_us()
    while echo_Pin.value()==1:
        pulse_end=utime.ticks_us()

    pulse_duration=pulse_end-pulse_start

    distance= (pulse_duration*34300) / 2 / 1000000
    return distance

def activate_buzzer():
    pwm.freq(1000)
    pwm.duty_u16(32768)

def deactivate_buzzer():
    pwm.duty_u16(0)

while True:
    distance = measure_distance()
    print("distance: ",distance," cm")
    if distance < 30:
        activate_buzzer()
    else:
        deactivate_buzzer()
    utime.sleep(2)