from machine import Pin, Timer
import utime

pin1 = Pin(1, Pin.OUT)
pin2 = Pin(5, Pin.OUT)
pin3 = Pin(28, Pin.OUT)

timer = Timer(-1)
i = 0 
fast = 500  
slow = 2000 

def fn(Timer):
    global i, fast, slow

    if i % 3 == 0:
        pin3.value(0)
        pin1.value(1)
    elif i % 3 == 1:
        pin1.value(0)
        pin2.value(1)
    else:
        pin2.value(0)
        pin3.value(1)
    
    i += 1
    if i % 3 == 0:
        if i % 6 == 0:  
            timer.init(period=slow, mode=Timer.PERIODIC, callback=fn)
        else:
            timer.init(period=fast, mode=Timer.PERIODIC, callback=fn)

timer.init(period=fast, mode=Timer.PERIODIC, callback=fn)