import RPi.GPIO as GPIO
import time

# Define GPIO pins
TRIG = 21  # Trigger pin
ECHO = 20  # Echo pin

# Set up GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)

def get_distance():
    # Send a short pulse to trigger
    GPIO.output(TRIG, True)
    time.sleep(0.00001)
    GPIO.output(TRIG, False)

    # Wait for echo start
    while GPIO.input(ECHO) == 0:
        pulse_start = time.time()
    
    # Wait for echo end
    while GPIO.input(ECHO) == 1:
        pulse_end = time.time()
    
    # Calculate distance
    pulse_duration = pulse_end - pulse_start
    distance = (pulse_duration * 34300) / 2  # Speed of sound = 343m/s
    return distance

try:
    while True:
        dist = get_distance()
        print(f"Distance: {dist:.2f} cm")
        time.sleep(1)
except KeyboardInterrupt:
    print("Measurement stopped by user")
    GPIO.cleanup()