from machine import Pin
import time
data = Pin(5, Pin.OUT)   
clock = Pin(3, Pin.OUT)  
latch = Pin(4, Pin.OUT)  


def shift_out(value):
    latch.value(0)  
    
   
    for i in range(7, -1, -1):
        bit = (value >> i) & 1  
        data.value(bit)         
        clock.value(1)          
        clock.value(0)         
    
    latch.value(1)  


position = 0      
direction = 1    

while True:
    value = (1 << position) | (1 << (position + 1)) | (1 << (position + 2))
    shift_out(value)
    
    
    time.sleep(0.2)
    
    position = position + direction
    
    
    if position >= 6:
        direction = -1  
    if position <= 0:
        direction = 1