'''
PIN13 - R1 (OUTPUT)
PIN14 - R2 (OUTPUT)
PIN15 - R3 (OUTPUT)
PIN16 - R4 (OUTPUT)

PIN32 - C1 (INPUT)
PIN33 - C2 (INPUT)
PIN34 - C3 (INPUT)
PIN35 - C4 (INPUT)
'''

import machine
import time

# Define rows and columns
ROWS = [13, 14, 15, 16]  # GPIO pins for rows - OUTPUTS
COLS = [32, 33, 34, 35]  # GPIO pins for columns - INPUTS

# Keypad layout
KEYPAD = [
    ['1', '2', '3', 'A'],
    ['4', '5', '6', 'B'],
    ['7', '8', '9', 'C'],
    ['*', '0', '#', 'D']]

# Configure rows as outputs
row_pins = [machine.Pin(pin, machine.Pin.OUT) for pin in ROWS]

# Configure columns as inputs with pull-up resistors
col_pins = [machine.Pin(pin, machine.Pin.IN, machine.Pin.PULL_UP) for pin in COLS]

def scan_keypad():
    for row_idx, row_pin in enumerate(row_pins):
        # Activate the current row
        row_pin.value(1)
        for col_idx, col_pin in enumerate(col_pins):
            if col_pin.value() == 0:  # Check if the column is pulled LOW
                row_pin.value(0)  # Deactivate the row before returning
                return KEYPAD[row_idx][col_idx]  # Return the key
        row_pin.value(0)  # Deactivate the current row
    return None  # No key pressed

# Main loop
while True:
    key = scan_keypad()
    if key:
        print(f"Key Pressed: {key}")
    time.sleep(0.1)  # Debounce delay