# =======================================================
# HC-SR04 + BUZZER (NÂNG CAO - MicroPython)
# =======================================================

from machine import Pin
import time

trig = Pin(15, Pin.OUT)
echo = Pin(14, Pin.IN)
buzzer = Pin(16, Pin.OUT)

last_toggle = 0
buzzer_state = 0

def get_distance():
    trig.low()
    time.sleep_us(2)

    trig.high()
    time.sleep_us(10)
    trig.low()

    timeout = time.ticks_us()
    while echo.value() == 0:
        if time.ticks_diff(time.ticks_us(), timeout) > 30000:
            return 0
    start = time.ticks_us()

    while echo.value() == 1:
        if time.ticks_diff(time.ticks_us(), start) > 30000:
            return 0
    end = time.ticks_us()

    duration = time.ticks_diff(end, start)
    distance = duration * 0.034 / 2

    return distance

while True:

    d = get_distance()

    # vùng an toàn
    if d >= 30 or d == 0:
        buzzer.value(0)
        continue

    # tính khoảng thời gian beep
    interval = int(d * 10)
    if interval < 50:
        interval = 50

    now = time.ticks_ms()

    if time.ticks_diff(now, last_toggle) >= interval:
        buzzer_state = not buzzer_state
        buzzer.value(buzzer_state)
        last_toggle = now