from machine import Pin, Timer
from time import sleep

def motor (ap,bp,am,bm,ret):
    a1.value(ap),b1.value(bp),a2.value(am),b2.value(bm)
    sleep(ret)

a1=Pin(23,Pin.OUT)
a2=Pin(21,Pin.OUT)
b1=Pin(22,Pin.OUT)
b2=Pin(19,Pin.OUT)

while(True):
    #     a+,b+,a-,b-,ret
    motor(1, 1, 0, 0, 0.2)
    motor(0, 1, 1, 0, 0.2)
    motor(0, 0, 1, 1, 0.2)
    motor(1, 0, 0, 1, 0.2)