4x4 Matrix Keypad Input Experiment

Introduction

A 4x4 matrix keypad is an input device that consists of 16 buttons arranged in a 4-row by 4-column grid. This experiment demonstrates how to interface the keypad with an Arduino to read button presses and display them on the Serial Monitor.

Components Needed

• Arduino (e.g., Uno, Nano)
• 4x4 Matrix Keypad
• Breadboard and jumper wires

Circuit Setup

Connect the 4x4 keypad to the Arduino as follows:

• Keypad Pin 1 (Row 1) to Arduino pin 2
• Keypad Pin 2 (Row 2) to Arduino pin 3
• Keypad Pin 3 (Row 3) to Arduino pin 4
• Keypad Pin 4 (Row 4) to Arduino pin 5
• Keypad Pin 5 (Column 1) to Arduino pin 6
• Keypad Pin 6 (Column 2) to Arduino pin 7
• Keypad Pin 7 (Column 3) to Arduino pin 8
• Keypad Pin 8 (Column 4) to Arduino pin 9

Code for 4x4 Matrix Keypad

Upload the following code to your Arduino to detect button presses:

// Include the Keypad library
#include 

// Define the number of rows and columns in the keypad
const byte ROWS = 4; // Four rows
const byte COLS = 4; // Four columns

// Define the keymap
char keys[ROWS][COLS] = {
    {'1', '2', '3', 'A'},
    {'4', '5', '6', 'B'},
    {'7', '8', '9', 'C'},
    {'*', '0', '#', 'D'}
};

// Connect keypad ROW pins to Arduino pins 2, 3, 4, 5
byte rowPins[ROWS] = {2, 3, 4, 5};

// Connect keypad COLUMN pins to Arduino pins 6, 7, 8, 9
byte colPins[COLS] = {6, 7, 8, 9};

// Create the Keypad object
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup() {
    Serial.begin(9600);
    Serial.println("4x4 Keypad Ready. Press a key:");
}

void loop() {
    char key = keypad.getKey(); // Read the key pressed

    if (key) { // If a key is pressed
        Serial.print("Key Pressed: ");
        Serial.println(key);
    }
}
            

Explanation

• Keypad Library: Simplifies the interfacing of the keypad with the Arduino.
• Keymap: Defines the characters corresponding to each button.
• Keypad.getKey(): Reads the key pressed and returns its corresponding character.
• if (key): Ensures a keypress is detected before displaying output.

Troubleshooting

• If no keys are detected, check the wiring between the keypad and the Arduino.
• If incorrect characters are displayed, verify the keymap matches your keypad's layout.
• Ensure the Keypad library is installed in your Arduino IDE. If not, install it via the Library Manager.

Applications of 4x4 Keypad

Matrix keypads are commonly used in:

• Security systems (e.g., password entry)
• Calculator-style input devices
• Custom user interfaces