from machine import *
from time import *
# Pin allocation
trig = Pin(8, Pin.OUT)      # TRIG on GP8
echo = Pin(7, Pin.IN)       # ECHO on GP7
buzzer = PWM(Pin(19))       # Buzzer on GP19
led = Pin(0, Pin.OUT)       # LED on GP0
buzzer.freq(1000)

while True:
    # Create trigger pulse
    trig.value(0)
    sleep_us(2)
    trig.value(1)
    sleep_us(10)
    trig.value(0)

    # Measure echo time
    duration = time_pulse_us(echo, 1)
    # Convert time to distance in cm
    distance = (duration * 0.0343) / 2
    # Print result
    print("duration =", duration, "distance =", distance, "cm")
    if distance <= 50:
        print("Danger - Buzzer ON")        
        buzzer.duty_u16(20000)        
        led.value(0)

    elif distance >= 51 and distance <= 100:
        print("Warning - LED ON")        
        buzzer.duty_u16(0)
        led.value(1)

    else:
        print("Safe")
        buzzer.duty_u16(0)        
        led.value(0)

    sleep(0.5)