from machine import Pin, PWM
from time import sleep

ROWS = [19, 18, 5, 17]
COLS = [16, 4, 2, 15]

keys = [
    ['1', '2', '3', 'A'],
    ['4', '5', '6', 'B'],
    ['7', '8', '9', 'C'],
    ['*', '0', '#', 'D']
]

buzzer = PWM(Pin(14),freq=440,duty=512)

row_pins = [Pin(pin, Pin.OUT) for pin in ROWS]
col_pins = [Pin(pin, Pin.IN, Pin.PULL_UP) for pin in COLS]

for row in row_pins:
    row.value(1)

def read_keypad():
    for i, row in enumerate(row_pins):
        row.value(0)
        
        for j, col in enumerate(col_pins):
            if col.value() == 0:
                while col.value() == 0:
                    sleep(0.01)
                
                row.value(1) 
                return keys[i][j]
                
        row.value(1)
        
    return None

while True:
    key = read_keypad()
    if key:
        print("Tecla presionada:", key)
        buzzer.freq(10000)
        buzzer.duty(512)
        sleep(0.3)
    else:
        buzzer.duty(0)