from machine import Pin, PWM
import time

# Define pins for ultrasonic sensor and LED
TRIG_PIN = 5  # GPIO Pin for Trigger
ECHO_PIN = 18  # GPIO Pin for Echo
LED_PIN = 21  # GPIO Pin for LED

# Setup ultrasonic sensor pins
trig = Pin(TRIG_PIN, Pin.OUT)
echo = Pin(ECHO_PIN, Pin.IN)

# Setup PWM for LED
led = PWM(Pin(LED_PIN), freq=1000)  # 1kHz frequency for the LED

# Function to measure distance using ultrasonic sensor
def measure_distance():
    """Measures distance using the ultrasonic sensor and returns it in cm."""
    trig.value(0)
    time.sleep_us(2)
    trig.value(1)
    time.sleep_us(10)
    trig.value(0)
    
    while echo.value() == 0:
        signal_start = time.ticks_us()
    while echo.value() == 1:
        signal_end = time.ticks_us()
    
    duration = time.ticks_diff(signal_end, signal_start)  # Time difference in microseconds
    distance = (duration * 0.0343) / 2  # Convert to cm (speed of sound = 343m/s)
    return distance

# Function to set LED brightness (0 to 1023 for ESP32 PWM range)
def set_led_brightness(brightness_percentage):
    """Sets the LED brightness according to the percentage (0-100%)."""
    duty_cycle = int((brightness_percentage / 100) * 1023)  # Scale percentage to 0-1023
    led.duty(duty_cycle)

# Function to smoothly change LED brightness to a target brightness
def smooth_brightness_change(current_brightness, target_brightness):
    """Smoothly changes the LED brightness to the target brightness."""
    step = 1 if target_brightness > current_brightness else -1
    for brightness in range(current_brightness, target_brightness + step, step):
        duty_cycle = int((brightness / 100) * 1023)  # Scale percentage to 0-1023
        led.duty(duty_cycle)
        time.sleep_ms(10)  # Small delay to create smooth transition

try:
    current_brightness = 0  # Track the current brightness to avoid abrupt changes
    while True:
        distance = measure_distance()
        print("Distance: {:.2f} cm".format(distance))
        
        if distance < 199:  # Dead zone to avoid rapid switching
            target_brightness = 100  # 100% brightness
        elif distance > 200:  # Dead zone to avoid rapid switching
            target_brightness = 30  # 30% brightness
        else:
            continue  # Do nothing if distance is within dead zone
        
        if current_brightness != target_brightness:  # Only update if brightness has changed
            smooth_brightness_change(current_brightness, target_brightness)
            current_brightness = target_brightness  # Update the current brightness

except KeyboardInterrupt:
    print("Program stopped.")
    led.deinit()  # Deinitialize the PWM for the LED