from machine import Pin, PWM
import utime

pulse=Pin(4, Pin.OUT)#trigger
receiver =Pin(5, Pin.IN, Pin.PULL_DOWN)#echo
speaker = PWM(Pin(10))#buzzer
def CheckDistance():
    SpeedofSoundInMM = 0.344
    pulse.low()
    utime.sleep_us(20)
    pulse.high()
    utime.sleep_us(10)
    pulse.low()
    exitloop =False
    loopcount =0
    while receiver.value() == 0 and exitloop == False:
        loopcount = loopcount + 1
        delaytime = utime.ticks_us()
        if loopcount > 3000 : exitloop ==True
    while receiver.value() == 1 and exitloop == False:
        loopcount = loopcount + 1
        receivetime = utime.ticks_us()
        if loopcount > 3000 : exitloop ==True
        
    if exitloop == True:
        return 0
    else:
        distance = ((receivetime - delaytime) * SpeedofSoundInMM)/2
        return distance
while True:
    distance = CheckDistance()
    print(distance)
    if CheckDistance() < 2500:
        speaker.duty_u16(3000)
        speaker.freq(1700)
        utime.sleep(0.05)
        speaker.duty_u16(0)
        utime.sleep(CheckDistance() / 1000)
        speaker.duty_u16(0)