from machine import Pin, PWM, time_pulse_us
import time

# -------------------------
# Pin configuration
# -------------------------
TRIG_PIN = 3
ECHO_PIN = 2
BUZZER_PIN = 15

trig = Pin(TRIG_PIN, Pin.OUT)
echo = Pin(ECHO_PIN, Pin.IN)

buzzer = PWM(Pin(BUZZER_PIN))
buzzer.duty_u16(0)


# -------------------------
# Measure distance
# -------------------------
def get_distance():

    # Send trigger pulse
    trig.value(0)
    time.sleep_us(2)

    trig.value(1)
    time.sleep_us(10)

    trig.value(0)

    # Measure echo pulse
    duration = time_pulse_us(echo, 1, 30000)

    if duration < 0:
        return -1

    # Calculate distance
    distance = (duration * 0.0343) / 2

    return distance


# -------------------------
# Buzzer functions
# -------------------------
def buzzer_on():
    buzzer.freq(2000)
    buzzer.duty_u16(30000)


def buzzer_off():
    buzzer.duty_u16(0)


# -------------------------
# Main program
# -------------------------
while True:

    distance = get_distance()

    if distance < 0:
        print("No object detected")
        buzzer_off()

    else:
        print("Distance: {:.2f} cm".format(distance))

        # Object very close
        if distance <= 10:
            print("WARNING! Object very close!")
            buzzer_on()

        # Object between 10 and 20 cm
        elif distance <= 20:
            buzzer_on()
            time.sleep(0.1)
            buzzer_off()
            time.sleep(0.1)

        # Object between 20 and 50 cm
        elif distance <= 50:
            buzzer_on()
            time.sleep(0.1)
            buzzer_off()
            time.sleep(0.5)

        # Object farther than 50 cm
        else:
            buzzer_off()

        time.sleep(0.1)