from machine import Pin
from utime import sleep

rows = [Pin(i, Pin.OUT) for i in (2,3,4,5)]
cols = [Pin(i, Pin.IN, Pin.PULL_UP) for i in (6,7,8,9)]

def scan_keypad():
    for row_index, row_pin in enumerate(rows):
        row_pin.value(0)
        for col_index, col_pin in enumerate(cols):
            if col_pin.value() == 0:
                return [row_index, col_index]
        row_pin.value(1)
    return None

for row in rows:
    row.value(1)

while True:
    key = scan_keypad()
    if key:
        print(f"Button pressed at [row, col]: {key}")
        while scan_keypad():
            sleep(0.05)
    sleep(0.05)