ESP32-S3 4×4 Keypad with Arduino IDE

Introduction

The 4×4 Membrane Keypad is a simple user interface device with 16 keys arranged in 4 rows and 4 columns.
Each key press connects a unique row-column pair, which the ESP32-S3 can detect using digital input pins.
It’s ideal for projects requiring password input, menu navigation, or number entry.
In this tutorial, we’ll learn how to connect the 4×4 keypad to an ESP32-S3 and read key presses using the Arduino IDE.

Required Components

• ESP32-S3 Board
• 4×4 Keypad
• Jumper wires
• Breadboard (optional)

Pinout

Circuit Diagram / Wiring

• Keypad  Column 4 → 34 (ESP32-S3)
• Keypad  Column 3 → 35 (ESP32-S3)
• Keypad  Column 2 → 32 (ESP32-S3)
• Keypad  Column 1 → 33 (ESP32-S3)
• Keypad  Row 4 → 25 (ESP32-S3)
• Keypad  Row 3 → 26 (ESP32-S3)
• Keypad  Row 2 → 27 (ESP32-S3)
• Keypad  Row 1 → 14 (ESP32-S3)

Code / Programming

• Install Required Library (via Arduino Library Manager).
• Go to the “Libraries” tab on the left-hand side of the screen.
• Click on the “Library Manager” button (book icon) at the top of the Libraries tab.
• In the Library Manager window, type “Keypad” in the search bar.
• Locate the “Keypad” library click on the “Install” button next to it.
• Wait for the library to be installed, and you’re ready to use the Keypad library in your projects.

/*
Filename: ESP32-S3_keypad_input.ino
Description: Reads input from a 4x4 keypad and prints pressed keys to the Serial Monitor
Author: www.oceanlabz.in
Modification: 1/4/2025
*/
 
 
#include <Keypad.h>
 
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] = {14, 27, 26, 25}; // Connect to R1-R4
byte colPins[COLS] = {33, 32, 35, 34}; // Connect to C1-C4
 
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
 
void setup() {
  Serial.begin(115200);
}
 
void loop() {
  char key = keypad.getKey();
 
  if (key) {
    Serial.print("Key Pressed: ");
    Serial.println(key);
  }
}

Explanation

• A 4×4 keypad has 16 keys arranged in a matrix of 4 rows and 4 columns.
• Each key press connects a specific row and column, which the ESP32-S3 detects using digital I/O pins.
• The Keypad library scans the matrix and returns the character of the pressed key.

Troubleshooting

• Ensure keypad pins are connected in the correct row/column order to the ESP32-S3.
• Avoid using boot-related GPIOs like GPIO0, GPIO2, or GPIO15 for keypad connections.
• If no key press is detected, check for loose wires, incorrect wiring, or wrong pin numbers in code.