#include <stdio.h>
 #include "pico/stdlib.h"
  
 // Define rows and columns
 #define ROWS 4
 #define COLS 3
 uint row_pins[ROWS] = {2, 3, 4, 5};  // GPIO pins for rows
 uint col_pins[COLS] = {6, 7, 8};     // GPIO pins for columns
  
 // Function to initialize GPIOs for matrix keypad
 void init_keypad() {
     for (int i = 0; i < ROWS; i++) {
         gpio_init(row_pins[i]);
         gpio_set_dir(row_pins[i], GPIO_OUT);
         gpio_put(row_pins[i], 0);  // Set all rows to LOW initially
     }
    for (int i = 0; i < COLS; i++) {
         gpio_init(col_pins[i]);
         gpio_set_dir(col_pins[i], GPIO_IN);
         gpio_pull_down(col_pins[i]);  // Pull-down resistors
     }
 }
  
 // Function to scan keypad and detect button presses
 char scan_keypad() {
     char keys[ROWS][COLS] = {
         {'1', '2', '3'},
         {'4', '5', '6'},
         {'7', '8', '9'},
         {'*', '0', '#'}
     };
  
     for (int r = 0; r < ROWS; r++) {
         // Set the current row HIGH
         gpio_put(row_pins[r], 1);
  
         // Check each column for a HIGH signal
         for (int c = 0; c < COLS; c++) {
             if (gpio_get(col_pins[c])) {
                 // Debounce delay
                 sleep_ms(10);
                 if (gpio_get(col_pins[c])) {  // Confirm keypress
                     gpio_put(row_pins[r], 0);  // Reset row
                     return keys[r][c];  // Return detected key
                 }
             }
         }
  
         // Reset the current row LOW
         gpio_put(row_pins[r], 0);
     }
     return '\0';  // No key pressed
 }
  
 int main() {
     stdio_init_all();
     init_keypad();
  
     while (true) {
         char key = scan_keypad();
         if (key != '\0') {
             printf("Key Pressed: %c\n", key);
         }
         sleep_ms(50);  // Reduce CPU usage
     }
 }