- El terminal 1 es el de la izquierda del teclado como se indica en la imagen superior.

/*
  Juan A. Villalpando
  kio4.com
*/

#include <Keypad.h>

const byte numRows= 4; // Tiene 4 filas
const byte numCols= 4; // Tiene 4 columnas

char keymap[numRows][numCols]= 
{
{'1', '2', '3', 'A'}, 
{'4', '5', '6', 'B'}, 
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};


byte rowPins[numRows] = {9,8,7,6}; // Estos terminales del Arduino corresponden a Filas
byte colPins[numCols]= {5,4,3,2}; // Estos terminales del Arduino corresponden a Columnas

Keypad myKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

void setup()
{
Serial.begin(9600);
}

// Escribe la tecla pulsada en el Serial Monitor.
void loop()
{
char keypressed = myKeypad.getKey();
if (keypressed != NO_KEY)
{
Serial.print(keypressed);
}
}

/*this keypad tutorial number one by omar tarek 29-06-2014 */
byte h=0,v=0;    //variables used in for loops
const unsigned long period=50;  //little period used to prevent error
unsigned long kdelay=0;        // variable used in non-blocking delay 
const byte rows=4;             //number of rows of keypad
const byte columns=4;            //number of columnss of keypad
const byte Output[rows]={2,3,4,5}; //array of pins used as output for rows of keypad
const byte Input[columns]={6,7,8,9}; //array of pins used as input for columnss of keypad
byte keypad() // function used to detect which button is used 
{
 static bool no_press_flag=0;  //static flag used to ensure no button is pressed 
  for(byte x=0;x<columns;x++)   // for loop used to read all inputs of keypad to ensure no button is pressed 
  {
     if (digitalRead(Input[x])==HIGH);   //read evry input if high continue else break;
     else
     break;
     if(x==(columns-1))   //if no button is pressed 
     {
      no_press_flag=1;
      h=0;
      v=0;
     }
  }
  if(no_press_flag==1) //if no button is pressed 
  {
    for(byte r=0;r<rows;r++) //for loop used to make all output as low
    digitalWrite(Output[r],LOW);
    for(h=0;h<columns;h++)  // for loop to check if one of inputs is low
    {
      if(digitalRead(Input[h])==HIGH) //if specific input is remain high (no press on it) continue
      continue;
      else    //if one of inputs is low
      {
          for (v=0;v<rows;v++)   //for loop used to specify the number of row
          {
          digitalWrite(Output[v],HIGH);   //make specified output as HIGH
          if(digitalRead(Input[h])==HIGH)  //if the input that selected from first sor loop is change to high
          {
            no_press_flag=0;                //reset the no press flag;
            for(byte w=0;w<rows;w++) // make all outputs as low
            digitalWrite(Output[w],LOW);
            return v*4+h;  //return number of button 
          }
          }
      }
    }
  }
 return 50;
}
void setup() 
{
  for(byte i=0;i<rows;i++)  //for loop used to make pin mode of outputs as output
  {
  pinMode(Output[i],OUTPUT);
  }
  for(byte s=0;s<columns;s++)  //for loop used to makk pin mode of inputs as inputpullup
  {
    pinMode(Input[s],INPUT_PULLUP);
  }
  Serial.begin(9600); //to use serial monitor we set the buad rate
}
void loop()
{
  if(millis()-kdelay>period) //used to make non-blocking delay
  {
    kdelay=millis();  //capture time from millis function
switch (keypad())  //switch used to specify which button
   {
            case 0:
            Serial.println(1);
       break;  
            case 1:
            Serial.println(2);
       break;
            case 2:
            Serial.println(3);
       break;
            case 3:
            Serial.println("F1");
       break;
            case 4:
            Serial.println(4);
       break;
            case 5:
            Serial.println(5);
       break;
            case 6:
            Serial.println(6);
       break;
            case 7:
            Serial.println("F2");
       break;
            case 8:
            Serial.println(7);
       break;
            case 9:
            Serial.println(8);
       break;
            case 10:
            Serial.println(9);
       break;
            case 11:
            Serial.println("F3");
       break;
            case 12:
            Serial.println("Mode");
       break;
            case 13:
            Serial.println(0);
       break;
            case 14:
            Serial.println("Cancel");
       break;
            case 15:
            Serial.println("Enter");
       break;
            default:
            ;
}
}
}