from machine import*
from time import*
trig = Pin(8,Pin.OUT)
echo = Pin(7,Pin.OUT)
r = Pin(14,Pin.OUT)
g = Pin(15,Pin.OUT)
buzzer = PWM(Pin(19))
buzzer.freq(1000)
while True:
    trig.value(0)
    sleep_us(2)
    trig.value(1)
    sleep_us(10)
    trig.value(0)
    duration = time_pulse_us(echo,1)
    distance = (duration*0.0343)/2
    print("duration=",duration,"distance=",distance,"cm")
    if distance>60:
        print("safe")
        g.value(1)
        r.value(0)
        buzzer.duty_u16(0)
    elif distance>=30 and distance<=60:
        print("warning")
        g.value(0)
        r.value(1)
        buzzer.duty_u16(0)
    else:
        print("wrong input")
    sleep(0.5)