from machine import Pin
import time
KEY_UP   = const(0)
KEY_DOWN = const(1)

keys = [
    ["1", "2", "3", "A"],
    ["4", "5", "6", "B"],
    ["7", "8", "9", "C"],
    ["*", "0", "#", "D"]
]
cols = [16,4,0,2]
rows = [23,22,21,19]

row_pins = [Pin(pin_name, mode=Pin.OUT) for pin_name in rows]
 
col_pins = [Pin(pin_name, mode=Pin.IN, pull=Pin.PULL_DOWN)for pin_name in cols]

def init():
    for row in range(0,4):
        for col in range(0,4):
            row_pins[row].value(0)
 
def scan(row, col):
    """ scan the keypad """
 
    row_pins[row].value(1)
    key = None
 
    if col_pins[col].value() == KEY_DOWN:
        key = KEY_DOWN
    if col_pins[col].value() == KEY_UP:
        key = KEY_UP
    row_pins[row].value(0)
 
    return key
    print("starting")

init()
 
while True:
   
    for row in range(4):
        for col in range(4):
            key = scan(row, col)
            if key == KEY_DOWN:
                print("Key Pressed", keys[row][col])
                last_key_press = keys[row][col]
                time.sleep(0.5)