import machine
import time

row_pins = [
    machine.Pin(0, machine.Pin.IN), 
    machine.Pin(1, machine.Pin.IN), 
    machine.Pin(2, machine.Pin.IN), 
    machine.Pin(3, machine.Pin.IN)
]

col_pins = [
    machine.Pin(4, machine.Pin.IN, machine.Pin.PULL_DOWN), 
    machine.Pin(5, machine.Pin.IN, machine.Pin.PULL_DOWN), 
    machine.Pin(6, machine.Pin.IN, machine.Pin.PULL_DOWN)
]

key_map = [
    ['1', '2', '3'], 
    ['4', '5', '6'], 
    ['7', '8', '9'], 
    ['*', '0', '#']
]

while True:
    for i in range(len(row_pins)):
        row_pins[i].init(machine.Pin.OUT)
        row_pins[i].value(1)
        
        for j in range(len(col_pins)):
            
            if col_pins[j].value():
                time.sleep_ms(20)
                
                if col_pins[j].value():
                    print(key_map[i][j])
                
                    while col_pins[j].value():
                        time.sleep_ms(10)
                        
        
        row_pins[i].init(machine.Pin.IN)
        
    time.sleep_ms(50)