import machine 
import utime 

#Define the keypad matrix layout (4x4) 
KEYPAD_ROWS = [machine.Pin(3), machine.Pin(2), machine.Pin(1), machine.Pin(0)]  
KEYPAD_COLS = [machine.Pin(7), machine.Pin(6), machine.Pin(5), machine.Pin(4)] 

#Keypad layout 
keypad = [ 
['1' ,'2', '3', 'A'], 
['4' ,'5' ,'6' ,'B'],
['7', '8', '9', 'C'],
['*' ,'0' ,'#' ,'D'] 
]
#Initialize the keypad pins 
for row pin in KEYPAD_ROWS: 
    row_pin.init(mode=machine. Pin. IN, pull-machine.Pin.PULL_UP) 
for col pin in KEYPAD COLS: 
    col_pin.init(mode=machine.Pin.OUT) 
    col_pin.value (1) #Set all column pins to high 
#Function to scan the keypad and return the pressed key (if any) 
def scan_keypad(): 
    for col_num, col pin in enumerate (KEYPAD_COLS): 
        col pin.value(0) # Set the current column to low 
        for row_num, row pin in enumerate (KEYPAD_ROWS): 
            If not row_pin.value(): 
                #Key pressed, wait for debouncing 
                utime.sleep_ms(50) 
                while not row_pin.value(): 
                    pass 
                # Return the pressed key 
                return keypad [row_num] [col_num] 
        col_pin.value(1) # Set the current column back to high 
    return None

# Main loop 
while True: 
    key scan_keypad() 
    if key: 
        print("Key pressed;", key)