from machine import Pin, Timer
from utime import sleep

pin_LED = Pin(12, Pin.OUT)

def main():
    while True:
        sleep(10)

myTimer = Timer(1)

def toggle_led(myTimer):
    pin_LED.on()
    sleep(0.5)
    pin_LED.off()
    sleep(0.5)

myTimer.init(freq=10, mode=Timer.PERIODIC, callback=toggle_led)

if __name__ == '__main__':
    main()