# Import required modules
from machine import Pin, Timer
import utime

# Set constants for better readability
ULTRASONIC_TRIGGER = 15
ULTRASONIC_ECHO = 14

def _measure_distance():
    # Trigger the ultrasound sensor
    trigger_pin.low()
    utime.sleep_us(2)
    trigger_pin.high()
    utime.sleep_us(5)
    trigger_pin.low()
    
    # Wait until echo pin goes HIGH
    while not echo_pin.value():
        pass
    start_time = utime.ticks_us()
    
    # Wait until echo pin goes LOW again
    while echo_pin.value():
        pass
    end_time = utime.ticks_us()
    
    # Calculate time passed between sending trigger and receiving echo
    time_elapsed = end_time - start_time
    
    # Convert time elapsed into distance
    velocity = 0.0343  # m/s (speed of sound in air at room temperature)
    distance = time_elapsed * velocity / 2
    
    return distance

try:
    # Initialize GPIO pins
    trigger_pin = Pin(ULTRASONIC_TRIGGER, Pin.OUT)
    echo_pin = Pin(ULTRASONIC_ECHO, Pin.IN)

    while True:
        print('Measuring...')
        
        # Measure distance
        distance = _measure_distance()
        print(f'Distance: {round(distance, 2)} cm')
        
        # Pause for 1 second
        utime.sleep(1)
except KeyboardInterrupt:
    print('\nExiting program...')
finally:
    del trigger_pin
    del echo_pin