from machine import Pin, PWM
import time

# Define GPIO pins
TRIG = Pin(14, Pin.OUT)  # Trigger
ECHO = Pin(15, Pin.IN)   # Echo
BUZZER = PWM(Pin(16))    # Buzzer using PWM

# Function to measure distance
def get_distance():
    TRIG.value(0)
    time.sleep_us(2000)  # Hold trigger low for 2 ms
    TRIG.value(1)
    time.sleep_us(5)     # Hold trigger high for 5 µs
    TRIG.value(0)

    while ECHO.value() == 0:
        pass  # Wait for ECHO to go HIGH

    start_time = time.ticks_us()
    while ECHO.value() == 1:
        pass  # Wait for ECHO to go LOW
    end_time = time.ticks_us()

    pulse_duration = time.ticks_diff(end_time, start_time)  # Get pulse width in µs
    distance = (pulse_duration * 0.0343) / 2  # Convert to cm
    return distance

# Function to control buzzer based on distance
def beep_buzzer(distance):
    if distance > 150:  # If far, no beeping
        BUZZER.duty_u16(0)  # Turn off buzzer
    else:
        freq = 1000 - (distance * 8)  # Decrease frequency as car gets closer
        if freq < 250:
            freq = 250  # Minimum frequency limit
        BUZZER.freq(int(freq))  # Set buzzer frequency
        BUZZER.duty_u16(30000)  # Set loudness (50%)

# Main loop
while True:
    distance = get_distance()
    print("Distance: {:.2f} cm".format(distance))
    beep_buzzer(distance)
    time.sleep(0.2)  # Small delay for reading updates