from machine import Pin
import time

pIn=Pin.IN
pUp=Pin.PULL_UP
pOut=Pin.OUT

p_row=[Pin(18,pIn,pUp),Pin(5,pIn,pUp),Pin(17,pIn,pUp),Pin(16,pIn,pUp)]
p_col=[Pin(19,pOut),Pin(21,pOut),Pin(22,pOut),Pin(23,pOut)]
n_row=[14,13,11,7] #binary: 1110, 1101, 1011, 0111

keypad=(('1','2','3','A'),
        ('4','5','6','B'),
        ('7','8','9','C'),
        ('*','0','#','D'))

for col in range(4):
    p_col[col].on()


while 1:
    for col in range(4):
        p_col[col].off()
        key=(
            (p_row[3].value()<<3)
            |(p_row[2].value()<<2)
            |(p_row[1].value()<<1)
            |(p_row[0].value())
        )
        p_col[col].on()
        if key!=15: #if any key is pressed (15 is 1111 in binary)
            if key in n_row:
                row=n_row.index(key) #row = index of key i.e. [14,13,11,7]
                print("key:",keypad[row][col])
                time.sleep_ms(200)
    
    time.sleep_ms(10)