from machine import Pin, Timer
import time

def blink(timer):
    global led, led_state
    led.value(led_state)
    led_state = not led_state

def measure_distance():
    trig.value(1)
    time.sleep_us(10)
    trig.value(0)
    
    timeout = time.ticks_add(time.ticks_us(), 30000)  
    while echo.value() == 0 and time.ticks_diff(time.ticks_us(), timeout) < 0:
        start = time.ticks_us()
    
    while echo.value() == 1:
        end = time.ticks_us()
        
    pulse_duration = time.ticks_diff(end, start)
    distance = (pulse_duration * 0.0343) / 2
    return distance

trig = Pin(18, Pin.OUT)
echo = Pin(19, Pin.IN)
led = Pin(0, Pin.OUT)
led_state = False

trig.value(0)  
time.sleep(2)  

blink_timer = Timer(-1)

while True:
    distance = measure_distance()
    
    if 0 < distance <= 200:
        period = int(distance * 9.5)
        blink_timer.init(period=period, mode=Timer.PERIODIC, callback=blink)
    else:
        blink_timer.deinit()
        led.value(0)
    
    time.sleep(2)