from machine import Pin, PWM
from utime import sleep_us, ticks_us, sleep
 
red_pin = Pin(23, Pin.OUT)
yellow_pin = Pin(22, Pin.OUT)
green_pin = Pin(19, Pin.OUT)
 
trigger = Pin(25, Pin.OUT)
echo = Pin(33, Pin.IN)
buzzer=PWM(Pin(14),freq=1000,duty=512)
def ultra():
    trigger.off()
    sleep_us(2)
    trigger.on()
    sleep_us(5)
    trigger.off()
    while echo.value() == 0:
        signal_off = ticks_us()
    while echo.value() == 1:
        signal_on = ticks_us()
    try:
        time_pass = signal_on - signal_off
    except NameError:
        return 0
    return time_pass/58
while True:
    dist = ultra()
    print(f'Distance: {dist:.2f}cm')
    sleep(0.1)
    if dist<=50:
        red_pin.on()
        buzzer.freq(600)
    elif dist<=100:
        red_pin.off()
        yellow_pin.on()
        green_pin.off()
        buzzer.freq(400)
    elif dist<=200:
        red_pin.off()
        yellow_pin.off()
        green_pin.on()
        buzzer.freq(200)
    else:
        red_pin.off()
        yellow_pin.off()
        green_pin.off()
buzzer.deinit()