gpio_sim.py

#!/usr/bin/python

# Top LED
l1 = 0
l2 = 0
l3 = 0
l4 = 0
l5 = 0
l6 = 0
l7 = 0

# Outputs
da = 0
db = 0

# FF Q
ic1q = 0
ic2q = 0

def encoder():
    v = 0
    v = ic1q                # x1 = ic1q
    v = 2*v + ic2q          # x2 = ic2q
    v = 2*v + int(not(l1))  # x3 = not l1
    v = 2*v + int(not(l2))  # x4 = not l2
    v = 2*v + int(not(l3))  # x5 = not l3
    v = 2*v + int(not(l7))  # x6 = not l7
    return v

def update_led():
  global l1, l2, l3, l4, l5, l6, l7
  l1 = da or not(ic2q)
  l2 = not(l1) or not(ic1q)
  l3 = db or ic2q
  l4 = not(ic1q) or not(ic2q)
  l5 = not(ic1q) or not(l4)
  l6 = not(ic2q) or not(l4)
  l7 = not(l5) or not(l6)

def update_ff_q():
  global ic1q, ic2q
  ic1q = da
  ic2q = db

c = '@'
flag = ""

try:
    update_led()

    for i in range(10) :
        if c == 'Y' :
            da = 0
            db = 1
        else:
            if (i & 1) == 0 :
                da = 0
            else :
                da = 1
            if (i & 2) == 0 :
                db = 0
            else :
                db = 1

        update_led()

        #time.sleep(0.1)

        c = chr(encoder()+32)
        flag = flag + c

        update_ff_q()

        update_led()

        #time.sleep(0.1)
        flag = flag + chr(encoder()+32)

except KeyboardInterrupt:
    print("stop\n")

print "The flag is SECCON{"+flag+"}"