from machine import Pin, ADC
import time

# Ultrasonic sensor pin definitions
trig = Pin(2, Pin.OUT)
echo = Pin(3, Pin.IN)

# Potentiometer pin definition (ADC0)
pot = ADC(Pin(26))

def get_distance():
    # Send Trigger pulse
    trig.value(0)
    time.sleep_us(2)
    trig.value(1)
    time.sleep_us(10)
    trig.value(0)
    
    # Measure pulse duration
    while echo.value() == 0:
        pulse_start = time.ticks_us()
    while echo.value() == 1:
        pulse_end = time.ticks_us()
        
    pulse_duration = time.ticks_diff(pulse_end, pulse_start)
    # Calculate distance in centimeters
    distance = (pulse_duration * 0.0343) / 2
    return distance

while True:
    # Read Potentiometer to set Span (maps 0-65535 raw value to 0-400 cm range)
    pot_raw = pot.read_u16()
    span_threshold = (pot_raw / 65535.0) * 400
    
    # Measure current distance
    dist = get_distance()
    
    # Log reading only if measured distance is within the Span limit
    if dist < span_threshold:
        print(f"[LOG] Distance: {dist:.1f} cm (Less than Span Limit: {span_threshold:.1f} cm)")
    else:
        print(f"Ignored: {dist:.1f} cm exceeds span ({span_threshold:.1f} cm)")
        
    time.sleep(1)