import machine
from utime import sleep

s0 = machine.Pin(27, machine.Pin.OUT)
s1 = machine.Pin(28, machine.Pin.OUT)
mux_in = machine.Pin(26, machine.Pin.IN, machine.Pin.PULL_DOWN)

prev_binary_code = 0
while True:
   binary_code = 0
   for selector_val in range(4):
       s0.value(selector_val % 2)
       s1.value(selector_val // 2)
       sleep(0.020)
       # (10^1  *digit_1) + (10^0*  digit_0)
       # example: 28 -> (10^1  *2) + (10^0*  8)
       # (2^1  *input_1) + (2^0*  input_0)
       binary_code += (pow(2, selector_val) * mux_in.value())
   if binary_code != prev_binary_code:
       print(f'decimal representation: {binary_code}')
       prev_binary_code = binary_code
   sleep(0.100)