from machine import Pin
import utime

# Hardware Setup
trigger = Pin(20, Pin.OUT)
echo = Pin(21, Pin.IN)

# LED Bar Graph setup (Pins 2 to 11 control the 10 segments)
bar_pins = [Pin(i, Pin.OUT) for i in range(2, 12)]

def get_distance_m():
    trigger.low()
    utime.sleep_us(2)
    trigger.high()
    utime.sleep_us(10)
    trigger.low()
    
    while echo.value() == 0:
        start = utime.ticks_us()
    while echo.value() == 1:
        end = utime.ticks_us()
        
    pulse_time = utime.ticks_diff(end, start)
    distance_m = (pulse_time * 0.0343) / 2 / 100
    return distance_m

while True:
    dist = get_distance_m()
    
    # Mathematical Threshold Scaling
    if dist > 1.0:
        level = 0
    elif dist <= 0.1:
        level = 10
    else:
        # Distance mapping: 1.0m to 0.1m scales to 0-10 LEDs
        level = int((1.0 - dist) * 11.1)
        
    # Write to Bar Graph
    for i in range(10):
        if i < level:
            bar_pins[i].value(1)
        else:
            bar_pins[i].value(0)
            
    utime.sleep(0.1)