from machine import Pin
from machine import Timer

TIMER_PERIOD = 300 # LED_F300ms
led_flag = False   # LED_CtO

led = Pin(25, Pin.OUT)
led.off()

def timer_callback(tim):
   global led_flag
   led_flag = not led_flag

timer = Timer(-1) # -1̎w͕(1)
timer.init(period = TIMER_PERIOD,  mode = Timer.PERIODIC, callback = timer_callback)

while True:
  if led_flag:
     led.on()
  else:
     led.off()