Cell Phone Keypad

This sketch simulates the character cycle on a cell phone keypad and uses the standard Keypad library.

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/* @file CellPhoneKeypad.pde
|| @Creator Andrew Mascolo (HazardsMind)
|| @Date Oct 5, 2014
|| @Edited: Sept 7, 2015
||
|| @description
|| Demonstrates the functionality of the keypad on a cellular keypad.
*/
#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns

// IMPORTANT, DO NOT CHANGE!
char lastKey, Character;
byte K_count = 0;
unsigned long timer, interval = 2 * 1000000UL; // interval = 2 seconds
bool lockout = true;

// This array is used to change between the characters in the second array
// IMPORTANT, DO NOT CHANGE!
char Keys[ROWS][COLS] = {
  {'1', '2', '3'},
  {'4', '5', '6'},
  {'7', '8', '9'},
  {'*', '0', '#'}
};

// The following array is what is printed when a key is pressed
// Format: { string of characters to be shown }
char * CharacterMask[ROWS][COLS] = {
  { "1", "2ABC", "3DEF" },
  { "4GHI", "5JKL", "6MNO" },
  { "7PQRS", "8TUV", "9WXYZ"},
  { "*", "0", "#" }
};

byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {10, 9, 8}; //connect to the column pinouts of the keypad

//initialize an instance of class NewKeypad
Keypad customKeypad = Keypad( makeKeymap(Keys), rowPins, colPins, ROWS, COLS);

void setup()
{
  Serial.begin(115200);
}

void loop()
{
  char customKey = customKeypad.getKey();

  //Check the key pressed. If the key is different, show it on a new line
  if (customKey && customKey != lastKey)
  {
    lastKey = customKey; // update lastKey
    K_count = 0; // This resets the counter so when a different key is pressed, you only see the NUMBER associated with that key.
    Serial.println();
  }

  if (customKey)
  {
    timer = micros(); // start a timer, when a key is pressed
    lockout = false; // allow the lockout timer to be checked
    lastKey = customKey; // update lastKey
    switch (customKey)
    {
      case '1':
        Character = *CharacterMask[0][0];                                                              // Character = '1'
        break;

      case '2':
      case '3':
        Character = *(CharacterMask[0][(customKey - '0') - 1] + K_count);                              // Character = '2' - ABC and '3' - DEF
        K_count++;
        if (K_count >= (byte)(strlen(CharacterMask[0][(customKey - '0') - 1])))
          K_count = 0;                                                                                 // Update the counter if the same key is pressed (counter rolls over)
        break;

      case '4':
      case '5':
      case '6':
        Character = *(CharacterMask[1][(customKey - '0') - 4] + K_count);
        K_count++;
        if (K_count >= (byte)(strlen(CharacterMask[1][(customKey - '0') - 4])))
          K_count = 0;
        break;

      case '7':
      case '8':
      case '9':
        Character = *(CharacterMask[2][(customKey - '0') - 7] + K_count);
        K_count++;
        if (K_count >= (byte)(strlen(CharacterMask[2][(customKey - '0') - 7])))
          K_count = 0;
        break;

      case '*':
        Character = *CharacterMask[3][0]; // shows *
        break;

      case '0':
        Character = *CharacterMask[3][1]; // shows 0
        break;

      case '#':
        Character = *CharacterMask[3][2]; // shows #
        break;

      default: // if something unexpected happens, set Character to 0
        Character = 0;
        break;
    }
    Serial.print(Character);
  }

  if ((micros() - timer >= interval) && !lockout) //If a key was pressed and then 2 seconds has past, reset the lastKey and counter.
  {
    lastKey = '~'; //dummy character;
    K_count = 0; // Resets the counter
    lockout = true; // lockout is set to true, thus this IF statement does not continue to execute
  }
}

Result:

1
2ABC
3DEF
4GHI
5JKL
6MNO
7PQRS
8TUV
9WXYZ
*
0
#