from machine import Pin
import time

# Define pin numbers
LED_PIN = 0   # GP0 on Raspberry Pi Pico
TRIGGER_PIN = 7   # GP7 on Raspberry Pi Pico
ECHO_PIN = 6   # GP6 on Raspberry Pi Pico
ULTRASOUND_THRESHOLD = 130  # Threshold distance in cm

# Initialize pins
led = Pin(LED_PIN, Pin.OUT)
trigger = Pin(TRIGGER_PIN, Pin.OUT)
echo = Pin(ECHO_PIN, Pin.IN)

# Function to measure distance
def measure_distance():
    # Send a 10us pulse to trigger
    trigger.value(1)
    time.sleep_us(10)
    trigger.value(0)
    
    # Wait for echo to go high
    while echo.value() == 0:
        pulse_start = time.ticks_us()
    
    # Wait for echo to go low
    while echo.value() == 1:
        pulse_end = time.ticks_us()
    
    # Calculate duration of pulse
    pulse_duration = pulse_end - pulse_start
    
    # Convert pulse duration to distance (in cm)
    distance = (pulse_duration * 0.0343) / 2
    
    return distance

# Main loop
while True:
    # Measure distance
    distance = measure_distance()
    
    # If distance is less than the threshold, turn on the LED
    if distance > ULTRASOUND_THRESHOLD:
        led.value(1)
    else:
        led.value(0)
    
    # Delay before next measurement
    time.sleep(0.1)