Arduino 16x2 LCD Display and 4x4 Matrix Keypad

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:-  [e-mail]
   */
  // 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.