from machine import Pin
from machine import Timer
import time

pin23=Pin(23,Pin.OUT)

def tim0_callback(timer):
    pin23.on()
    print('..Timer0 callback - LED ON')

tim0=Timer(0)
tim0.init(period=500,mode=Timer.PERIODIC,callback=tim0_callback)

while 1:
    pin23.off()
    print('..time.sleep_ms - LED OFF')
    time.sleep_ms(1000)