from machine import Pin
import utime

keys = [['1', '2', '3', 'A'],
        ['4', '5', '6', 'B'],
        ['7', '8', '9', 'C'],
        ['*', '0', '#', 'D']]
rows = [9, 8, 7, 6]
cols = [5, 4, 3, 2]
row_pins = [Pin(r, Pin.OUT) for r in rows]
col_pins = [Pin(c, Pin.IN, Pin.PULL_DOWN) for c in cols]
guess, secret_pin = [], ['9', '6', '9', '6', '9', '6']
led = Pin(15, Pin.OUT)

def scan_keys():
    for r in range(4):
        row_pins[r].high()
        for c in range(4):
            if col_pins[c].value():
                print("Pressed:", keys[r][c])
                guess.append(keys[r][c])
                utime.sleep(0.3)
                if len(guess) == 6:
                    check_pin(guess)
                    guess.clear()
        row_pins[r].low()

def check_pin(guess):
    if guess == secret_pin:
        print("Access granted!")
        led.on(); utime.sleep(2); led.off()
    else:
        print("Access denied!")

print("Enter secret PIN")
while True:
    scan_keys()