from machine import Pin,PWM
from time import sleep_us,ticks_us,sleep
trig=Pin(15,Pin.OUT)
echo=Pin(2,Pin.IN)
beep=PWM(Pin(13),duty=128)
distance=0
while True:
    trig.value(1)
    sleep_us(10)
    trig.value(0)
    while echo.value()==0:
        pass
    if echo.value()==1:
        ts=ticks_us()
        while echo.value()==1:
            pass
        te=ticks_us()
        tc=te-ts
        distance=tc*340/20000
    print(distance,"cm")
    w=distance
    if distance<30:
        beep=PWM(Pin(12),freq=342,duty=128)
        print("距离")   
    else:
        beep.deinit()