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In Embedded system design, matrix keypad (4x4, 4x3, 3x3 or 5x5) is used for key in the user inputs. Similarly character LCD display [16x2, 16x4, 20x2 or 20x4 LCDs] is used for indicating the system status / parameters. This intractable is about interfacing 16×2 LCD and 4x4 matrix keypad with Arduino microcontroller.

Parts and components

  • Arduino Uno board
  • 16x2 LCD
  • 1 K ohm potentiometer
  • 4x4 matrix keypad

Step 1: Schematic

  • The 16x2 is very common type LCD, with two rows, and each row displays 16 characters of either 5x7 or 5x8 dot matrix characters.
  • The LCD is available in a 16 pin package. It consists of back light and contrast adjustment function and each dot matrix has 5×8 dot resolution.
  • The 16x2 LCD display is connected to the Arduino (A0,A1,A2,A3,A4,A5) analog IO pins, where those pins are configured as digital in / out, where LCD operates at 4 bit data mode.
  • If the display is not visible, adjust the Contrast pot (1K), to make it visible.
  • Matrix key pad is arranged by push button switches in rows and columns.

  • In a simple technique, the 16 keys of matrix keypad is connected with 8 digital IOpins of Arduino.

  • Usually the keypad scan procedure is

  • The key is decoded through Column selection / Row read.

  • Write HIGH to Column One. And keep rest of the Column to LOW.

  • Scan (Read) the Row One to Row Four, to find the key.

  • Repeat until a key press (are multiple) is identified.

  • The Row pins are connected to 5,4,3 and 2nd digital IO pins of Arduino.

  • The Column pins are connected to 6,7,8 and 9th digital IO pins of Arduino.

Step 2: Software

  • The Arduino LiquidCrystal and Keypad library is used for displaying the status and detecting key press.
  • The LCD displays the “KEYPAD LCD TEST” as welcome screen at the first line
  • Number of seconds since start “SEC= 123” is displayed at the second line column one.
  • The detected key is displayed at (“KEY= 5”) second line column 9 on wards.

/*
Demonstrates the use a 16x2 LCD display and 4x4 LCD display. T

The Arduino circuit connection for LCD:

* LCD RS pin to analog pin A0

* LCD Enable pin to analog pin A1

* LCD D4 pin to analog pin A2

* LCD D5 pin to analog pin A3

* LCD D6 pin to analog pin A4

* LCD D7 pin to analog pin A5

The Arduino circuit connection for MAtrix Key Pad:

* ROW1 pin to digital pin 5

* ROW2 pin to digital pin 4

* ROW3 pin to digital pin 3

* ROW4 pin to digital pin 2

* COLUMN1 pin to digital pin 6

* COLUMN2 pin to digital pin 7

* COLUMN3 pin to digital pin 8

* COLUMN4 pin to digital pin 9

Name:- M.Pugazhendi

Date:- 04thJul2016

Version:- V0.1

e-mail:- muthuswamy.pugazhendi@gmail.com

*/

// include the library code:

#include

#include

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

LiquidCrystal lcd(A0,A1,A2,A3,A4,A5);

//4x4 Matrix key pad

const byte ROWS = 4; // Four rows

const byte COLS = 4; // Four columns

// Define the Keymap

char keys[ROWS][COLS] =

{

{'7','8','9','/'},

{'4','5','6','X'},

{'1','2','3','-'},

{'#','0','=','+'}

};

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

byte rowPins[ROWS] = { 5, 4, 3, 2 };

// Connect keypad COL0, COL1, COL2 and COL3 to Arduino pins.

byte colPins[COLS] = { 6, 7, 8, 9 };

// Create the Keypad

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

void setup()

{

// set up the LCD's number of columns and rows:

lcd.begin(16, 2);

// Print a message to the LCD.

lcd.print("KEYPAD LCD TEST");

}

void loop()

{

char key = kpd.getKey();

// set the cursor to column 0, line 1

// (note: line 1 is the second row, since counting begins with 0):

lcd.setCursor(0, 1);

// print the number of seconds since reset:

lcd.print("SEC= ");

lcd.print(millis() / 1000);

// Check for a valid key

if(key)

{

// set the cursor to column 9, line 1

// (note: line 1 is the second row, since counting begins with 0):

lcd.setCursor(9, 1);

//Print the detected key

lcd.print("KEY= ");

lcd.print(key);

}

}

Conclusion

  • The project is successfully simulated by using the Proteus.
  • The Keypad and LCD display can be used for many embedded projects as user input and status display.

Alhamdulliha! doing work.....
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