Tutorial for Generic Arduino UNO Kit (Keypad Interfacing with Arduino Uno)

In this tutorial we are going to interface a 4x4 (16 key) keypad with ARDUINO UNO. We all know keypad is one of the most important input devices used in electronics engineering. Keypad is the easiest and the cheapest way to give commands or instructions to an electronic system. Whenever a key is pressed in keypad module the Arduino Uno detects it and shoes the corresponding key on 16x2 LCD.

Components Required:-

ARDUINO UNO Board with Cable
power supply (5v),
4x4 Keypad Module,
162ALCD (16x2LCD),
Jumper Wires(MF -10 Pcs,MM-8 Pcs)

Software need to Run Arduino UNO: 

arduino IDE (version 1.6.4 prefrable)  (Open Source)
Free Download from Arduino.cc website

Circuit Diagram and Working Explanation:

In 16x2 LCD there are 16 pins over all if there is a back light, if there is no back light there will be 14 pins.
One can power or leave the back light pins.
Now in the 14 pins there are 8 data pins (7-14 or D0-D7),
2 power supply pins (1&2 or VSS&VDD or GND&+5v),
3rd pin for contrast control (VEE-controls how thick the characters should be shown) and 3 control pins (RS&RW&E).

In the Arduinouno keypad interfacing circuit, you can observe that I have only took two control pins. This give the flexibility of better understanding, the contrast bit and READ/WRITE are not often used so they can be shorted to ground. This puts LCD in highest contrast and read mode. We just need to control ENABLE and RS pins to send characters and data accordingly.

The connections which are done for LCD are given below:

PIN1 or VSS to ground

PIN2 or VDD or VCC to +5v power

PIN3 or VEE to ground (gives maximum contrast best for a beginner)

PIN4 or RS (Register Selection) to PIN8 of ARDUINO UNO

PIN5 or RW (Read/Write) to ground (puts LCD in read mode eases the communication for user)

PIN6 or E (Enable) to PIN9 of ARDUINO UNO

PIN11 or D4 to PIN10 of ARDUINO UNO

PIN12 or D5 to PIN11 of ARDUINO UNO

PIN13 or D6 to PIN12 of ARDUINO UNO

PIN14 or D7 to PIN13 of ARDUINO UNO

Circuit Diagram :

We are going to connect the keypad module between pins 0-7 of Arduino Uno, as shown in the circuit diagram. All the eight pins of keypad module are connected accordingly.

Now for setting up a connection between Keypad Module and UNO, we need to get the keypad library from the ARDUINO website. After that we can directly call the header file. We will discuss each command below.

Programming for the Arduino,keypad Matrix Connection :

1.   #include <Keypad.h>

2.   const byte ROWS = 4; // Four rows

3.   const byte COLS = 4; // Three columns

// Define the Keymap

1.   char keys[ROWS][COLS] = {

  {'1','2','3','A'},

  {'4','5','6','B'},

  {'7','8','9','C'},

 {'#','0','*','D'}

};

// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.

1.   byte rowPins[ROWS] = { 0, 1, 2, 3 };

// Connect keypad COL0, COL1 and COL2 to these Arduino pins.

1.   byte colPins[COLS] = { 4, 5, 6, 7 };

// Create the Keypad

1.   Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

char key = kpd.getKey();

Explanation of the Code:

First we will call the header file which enables user to access all keypad commands. We will write each key of keypad in matrix, for the UNO to understand the key press.

Telling the Uno which pins are used to connect the keypad module.

Telling the UNO to map each key on press.

Getting the UNO mapped key in to a memory.

 The working of Arduino Uno Keypad Interface is best explained in C code given below.

Code: 

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins

LiquidCrystallcd(8, 9, 10, 11, 12, 13);//RS,EN,D4,D5,D6,D7

#include <Keypad.h>//header for keypad commands enabling

const byte ROWS = 4; // Four rows

const byte COLS = 4; // Three columns

// Define the Keymap

char keys[ROWS][COLS] = {

  {'1','2','3','A'},

  {'4','5','6','B'},

  {'7','8','9','C'},

  {'#','0','*','D'}

};

// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.

byterowPins[ROWS] = { 0, 1, 2, 3 };

// Connect keypad COL0, COL1 and COL2 to these Arduino pins.

bytecolPins[COLS] = { 4, 5, 6, 7 };

//  Create the Keypad

Keypad kpd = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup()

{

  for(int k=8;k<14;k++)

  {

    pinMode(k,OUTPUT);//pins 8-14 are enabled as output

  }

  lcd.begin(16, 2);//initializing LCD

}

void loop()

{

  char key = kpd.getKey(); //storing pressed key value in a char

  if (key != NO_KEY)

{

      lcd.print(key); //showing pressed character on LCD

  }

}