from machine import Pin, PWM
import time

TRIG_PIN = 26
ECHO_PIN = 25
BUZZER_PIN = 18 

trigger = Pin(TRIG_PIN, Pin.OUT)
echo = Pin(ECHO_PIN, Pin.IN)
buzzer = PWM(Pin(BUZZER_PIN))

def get_distance():
    trigger.value(1)
    time.sleep_us(10)
    trigger.value(0)

    while echo.value() == 0:
        pass
    start = time.ticks_us()

    while echo.value() == 1:
        pass
    end = time.ticks_us()

    distance = ((end - start) / 2) / 29.1
    return distance

while True:
    distance = get_distance()
    print('Distance:', distance, 'cm')

    volume = int((200 - min(distance, 200)) / 200 * 1023)
    buzzer.duty(volume)