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Keypad

Overview

In this lesson, you will learn to use Keypad. Keypad can be applied into various kinds of devices, including mobile phone, fax machine, microwave oven and so on. It is commonly used in user input.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Elite Explorer Kit	300+	Elite Explorer Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
Arduino Uno R4 WiFi	-
Jumper Wires	BUY
Keypad	BUY

Wiring

Schematic Diagram

Code

Note

• You can open the file 21-keypad.ino under the path of elite-explorer-kit-main\basic_project\21-keypad directly.

• To install the library, use the Arduino Library Manager and search for “Adafruit Keypad” and install it.

21-keypad.ino

/*
  The code use an Adafruit Keypad and display keypress events via the Serial Monitor. 
  It initializes the keypad with a 4x4 layout, where each key is represented by a 
  specific character. It continuously checks for keypad events (key press or release) 
  and prints the corresponding key and event status to the Serial Monitor.

  Board: Arduino Uno R4 
  Component:  Keypad
  Library: https://github.com/adafruit/Adafruit_Keypad (Adafruit Keypad by Adafruit)
*/

// Include the Adafruit_Keypad library
#include "Adafruit_Keypad.h"

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

// Define the characters mapped to each button on the 4x4 keypad
char keys[ROWS][COLS] = {
  { '1', '2', '3', 'A' },
  { '4', '5', '6', 'B' },
  { '7', '8', '9', 'C' },
  { '*', '0', '#', 'D' }
};

// Define the Arduino pins connected to the row pinouts of the keypad
byte rowPins[ROWS] = { 2, 3, 4, 5 };
// Define the Arduino pins connected to the column pinouts of the keypad
byte colPins[COLS] = { 8, 9, 10, 11 };

// Initialize a custom keypad instance
Adafruit_Keypad myKeypad = Adafruit_Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Setup function
void setup() {
  // Initialize Serial communication at 9600 baud rate
  Serial.begin(9600);
  // Initialize the custom keypad
  myKeypad.begin();
}

// Main loop function
void loop() {
  // Update the state of keys
  myKeypad.tick();

  // Check if there are new keypad events
  while (myKeypad.available()) {
    // Read the keypad event
    keypadEvent e = myKeypad.read();
    // Print the key that triggered the event
    Serial.print((char)e.bit.KEY);
    // Print the type of event: pressed or released
    if (e.bit.EVENT == KEY_JUST_PRESSED) Serial.println(" pressed");
    else if (e.bit.EVENT == KEY_JUST_RELEASED) Serial.println(" released");
  }

  delay(10);
}

After uploading the codes to the UNO board, on the serial monitor, you can see the value of the key currently pressed on the Keypad.

Code Analysis

1. Including the Library

   We start by including the Adafruit_Keypad library, which allows us to easily interface with the keypad.

   #include "Adafruit_Keypad.h"
   

   Note

   • To install the library, use the Arduino Library Manager and search for “Adafruit Keypad” and install it.

2. Keypad Configuration

   const byte ROWS = 4;
   const byte COLS = 4;
   char keys[ROWS][COLS] = {
     { '1', '2', '3', 'A' },
     { '4', '5', '6', 'B' },
     { '7', '8', '9', 'C' },
     { '*', '0', '#', 'D' }
   };
   byte rowPins[ROWS] = { 2, 3, 4, 5 };
   byte colPins[COLS] = { 8, 9, 10, 11 };
   

   • The ROWS and COLS constants define the dimensions of the keypad.

   • keys is a 2D array storing the label for each button on the keypad.

   • rowPins and colPins are arrays that store the Arduino pins connected to the keypad rows and columns.

   
   

3. Initialize Keypad

   Create an instance of Adafruit_Keypad called myKeypad and initialize it.

   Adafruit_Keypad myKeypad = Adafruit_Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
   

4. setup() Function

   Initialize Serial communication and the custom keypad.

   void setup() {
     Serial.begin(9600);
     myKeypad.begin();
   }
   

5. Main Loop

   Check for key events and display them in the Serial Monitor.

   void loop() {
     myKeypad.tick();
     while (myKeypad.available()) {
       keypadEvent e = myKeypad.read();
       Serial.print((char)e.bit.KEY);
       if (e.bit.EVENT == KEY_JUST_PRESSED) Serial.println(" pressed");
       else if (e.bit.EVENT == KEY_JUST_RELEASED) Serial.println(" released");
     }
     delay(10);
   }