#include <stdio.h>
#include "pico/stdlib.h"

uint8_t Key_col[4] = { 8, 9, 10, 11 };
uint8_t Key_row[4] = { 12, 13, 14, 15 };
uint8_t Key_value[4][4] = { { 1,2,3,10},
{ 4,5,6,11},{ 7,8,9,12},{ 14,0,15,13}
};
uint8_t readKey();

int main() {
  stdio_init_all();
  for (uint8_t index=0; index < 4; index++){
    gpio_init( Key_col[index] );
    gpio_set_dir( Key_col[index], GPIO_OUT );
    gpio_init( Key_row[index] );
    gpio_set_dir( Key_row[index], GPIO_IN );
    gpio_pull_up( Key_row[index] );
  }
  for (uint8_t index=0; index < 4; index++){
    gpio_put(Key_col[index], 1);
  }
  uint8_t key;
  while (true) {
    key = readKey();
    if ( key <16){
      printf("KEY: %i\n", key);
    }
    sleep_ms(20);
  }
}

uint8_t readKey(){
  uint8_t col, row, keycol, keyrow, value;
  bool tmpEA, tmpEF, flag;
  keycol=4;
  keyrow=4;
  flag=0;
  value = 16;
  for ( col = 0 ; col < 4; col++ ){
      gpio_put(Key_col[col], 0);
      sleep_ms(1);
      for ( row = 0 ; row < 4; row++ ){
        sleep_ms(10);
        tmpEA = gpio_get( Key_row[row] );
        if  ( !tmpEA){
          if ( ( keycol != col) || ( keyrow != row) ) {
            keycol = col;
            keyrow = row;
            value = Key_value[keyrow][keycol];
            printf("KEY[%i][%i] = %i\n", keycol, keyrow, value);
            flag=1;
          }
          break;
        }
        if (flag){
          break;
        }
      }
      gpio_put(Key_col[col], 1);
    }
  return value;
}