Arduino - Keypad 1x4

In this tutorial, we will learn how to use a keypad 1x4 with an Arduino. In detaile, we will learn:

How to connect keypad 1x4 to Arduino.
How to program Arduino to read the pressed keys from keypad 1x4.

Hardware Required

1	×	Arduino Uno
1	×	USB 2.0 cable type A/B
1	×	Keypad 1x4
1	×	Jumper Wires
1	×	(Optional) 9V Power Adapter for Arduino
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Keypad 1x4

A 1x4 keypad is composed of four membrane buttons arranged in a single row. It is commonly used for user input in projects such as passcode entry, menu navigation, or control interfaces.

Pinout

The 1x4 keypad has 5 pins, which do not correspond directly to the key labels in order. Specifically:

Pin 1: connects to key 2
Pin 2: connects to key 1
Pin 3: connects to key 4
Pin 4: connects to key 3
Pin 5: is a common pin that connects to all keys

image source: diyables.io

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code

Each key on the 1x4 keypad functions as a button. This means we can use the digitalRead() function to check the status of each key. However, in practice, like with any button, we must handle the issue of bouncing, where a single press might be mistakenly detected as multiple presses. To avoid this, we need to debounce each key. This task becomes challenging when trying to debounce four keys without blocking other parts of the code. Fortunately, the ezButton library simplifies this process.

#include <ezButton.h> #define KEY_NUM 4 // the number of keys #define PIN_KEY_1 3 // The Arduino pin connected to the key 1 #define PIN_KEY_2 2 // The Arduino pin connected to the key 2 #define PIN_KEY_3 5 // The Arduino pin connected to the key 3 #define PIN_KEY_4 4 // The Arduino pin connected to the key 4 ezButton keypad_1x4[] = { ezButton(PIN_KEY_1), ezButton(PIN_KEY_2), ezButton(PIN_KEY_3), ezButton(PIN_KEY_4) }; void setup() { Serial.begin(9600); for (byte i = 0; i < KEY_NUM; i++) { keypad_1x4[i].setDebounceTime(100); // set debounce time to 100 milliseconds } } void loop() { int key = getKeyPressed(); if (key) { Serial.print("The key "); Serial.print(key); Serial.println(" is pressed"); } } int getKeyPressed() { for (byte i = 0; i < KEY_NUM; i++) keypad_1x4[i].loop(); // MUST call the loop() function first for (byte i = 0; i < KEY_NUM; i++) { // get key state after debounce int key_state = keypad_1x4[i].getState(); // the state after debounce if (keypad_1x4[i].isPressed()) return (i + 1); } return 0; }

Quick Steps

Connect Arduino to the keypad 1x4
Connect Arduino to PC via USB cable
Open Arduino IDE, select the right board and port
Navigate to the Libraries icon on the left bar of the Arduino IDE.
Search “ezButton”, then find the button library by ArduinoGetStarted.com
Click Install button to install ezButton library.

Copy the above code and open with Arduino IDE
Click Upload button on Arduino IDE to upload code to Arduino
Open Serial Monitor
Press keys on keypad 1x4 one by one
See the result in Serial Monitor

COM6

Send

1 2 3 4

Autoscroll Show timestamp

Clear output

9600 baud

Newline

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