from machine import Pin, PWM, time_pulse_us
import time

# 腳位設定
TRIG = Pin(3, Pin.OUT)
ECHO = Pin(2, Pin.IN)
buzzer = PWM(Pin(21))

def get_distance():
    TRIG.low()
    time.sleep_us(2)
    TRIG.high()
    time.sleep_us(10)
    TRIG.low()

    duration = time_pulse_us(ECHO, 1, 30000)
    distance = (duration / 2) / 29.1  # cm
    return distance

def beep(freq, duration):
    buzzer.freq(freq)
    buzzer.duty_u16(30000)
    time.sleep(duration)
    buzzer.duty_u16(0)

while True:
    dist = get_distance()
    print("當前距離: {:.1f} cm".format(dist))

    if dist > 100:
        buzzer.duty_u16(0)
        time.sleep(0.1)

    elif 30 <= dist <= 100:
        beep(500, 0.5)
        time.sleep(0.5)

    elif 10 <= dist < 30:
        beep(750, 0.3)
        time.sleep(0.3)

    else:  # < 10 cm
        buzzer.freq(1000)
        buzzer.duty_u16(30000)
        time.sleep(0.1)