Arduino UNO Q - Keypad 1x4
Want to add a simple 4-button keypad to your Arduino UNO Q project? In this tutorial, you will learn how to detect key presses with debouncing — and even send Telegram alerts when a key is pressed.
In this tutorial, you will learn:
- What a 1x4 keypad is and how it works
- How to wire the 1x4 keypad to Arduino UNO Q
- How to program the MCU (C/C++ Arduino code) to detect key presses with debouncing
- How to program both the Linux side (Python) and MCU side (C/C++) to read the keypad via Bridge
- How to send Telegram notifications when a key is pressed on Arduino UNO Q
- How to use OpenClaw on Arduino UNO Q with the 1x4 keypad
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables .
Overview of the 1x4 Keypad
A 1x4 keypad has four buttons arranged in a single row. It is used for entering codes, navigating menus, or triggering actions in different projects.
Pinout
The 1x4 keypad has 5 pins. The pin order does not match the key order on the label:
- Pin 1 → Key 2
- Pin 2 → Key 1
- Pin 3 → Key 4
- Pin 4 → Key 3
- Pin 5 → Common (GND)
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
| Keypad Pin | Arduino UNO Q MCU |
|---|---|
| Pin 1 (Key 2) | D2 |
| Pin 2 (Key 1) | D3 |
| Pin 3 (Key 4) | D4 |
| Pin 4 (Key 3) | D5 |
| Pin 5 (Common) | GND |
Arduino UNO Q Code
The Arduino UNO Q has two processors working together:
- The STM32 MCU reads the keypad pins directly with debouncing via the ezButton library
- The Qualcomm MPU runs Debian Linux and handles Wi-Fi, Python, and cloud connectivity
- In this section, only the MCU is programmed — the Linux side stays idle. A later section shows how both processors work together via Bridge.
Each key on the 1x4 keypad works like a button connected between a pin and GND. The ezButton library handles debouncing for all four keys automatically.
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
*/
// COPYRIGHT newbiely.com
// AUTHOR: newbiely
// This code is made available for public use without restriction.
// For complete instructions, tutorials, and further information, visit:
// https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
#include <ezButton.h>
#define KEY_NUM 4
#define PIN_KEY_1 3 // Arduino UNO Q MCU pin connected to key 1
#define PIN_KEY_2 2 // Arduino UNO Q MCU pin connected to key 2
#define PIN_KEY_3 5 // Arduino UNO Q MCU pin connected to key 3
#define PIN_KEY_4 4 // Arduino UNO Q MCU pin connected to key 4
ezButton keypad_1x4[KEY_NUM] = {
ezButton(PIN_KEY_1),
ezButton(PIN_KEY_2),
ezButton(PIN_KEY_3),
ezButton(PIN_KEY_4)
};
void setup() {
Serial.begin(115200);
delay(1500);
for (byte i = 0; i < KEY_NUM; i++) {
keypad_1x4[i].setDebounceTime(100);
}
Serial.println("Arduino UNO Q Keypad 1x4 ready");
}
void loop() {
int key = getKeyPressed();
if (key) {
Serial.print("Key pressed: ");
Serial.println(key);
}
}
int getKeyPressed() {
for (byte i = 0; i < KEY_NUM; i++)
keypad_1x4[i].loop(); // MUST call loop() first
for (byte i = 0; i < KEY_NUM; i++) {
if (keypad_1x4[i].isPressed())
return (i + 1);
}
return 0;
}
Detailed Instructions
First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial to get your development environment ready before proceeding.
- Connect: Wire the 1x4 keypad to the Arduino UNO Q MCU as shown in the wiring diagram above.
- Open Arduino App Lab: Launch Arduino App Lab and wait until it detects your Arduino UNO Q — this can take several minutes on first launch.
- Create a new App: Click the Create New App button.
- Give the App a name, for example: Keypad1x4
- Click Create to confirm.
- Find the sketch/sketch.ino file — this is where you will paste the MCU sketch.
Paste the sketch: Copy the MCU code above and paste it into that sketch file. Keep other files as default.
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- Search for ezButton created by ArduinoGetStarted.com and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Upload: Click the Run button in Arduino App Lab to compile and upload to the STM32.
- Open the Serial Monitor and press each key on the keypad. You will see the key number printed.
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q Keypad 1x4 ready
[2026-04-29 09:00:05] Key pressed: 1
[2026-04-29 09:00:08] Key pressed: 2
[2026-04-29 09:00:11] Key pressed: 3
[2026-04-29 09:00:14] Key pressed: 4
Bridge: Linux + MCU
This section shows how to program both processors of the Arduino UNO Q so the Linux side can read keypad presses remotely:
- The 1x4 keypad is connected to the MCU (STM32) — the MCU polls each key with debouncing in loop()
- The MPU cannot read keypad pins directly — it must request the last pressed key from the MCU via Bridge.call()
- The MPU has Wi-Fi — running full Debian Linux, it can react to key presses and send alerts over the Internet
- Arduino_RouterBridge enables RPC communication between the two processors
- ⚠️ /dev/ttyHS1 (Linux) and Serial1 (MCU) are RESERVED by the router — never open them in user code
In short: MCU polls the keypad → MPU reads the last key via Bridge → MPU can react to key presses from anywhere over the Internet.
Note: In the Bridge sketch, the ezButton polling loop is placed inside the Arduino loop() function to keep button state up to date — this is required and does not interfere with Bridge communication.
MCU Code (Bridge)
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
*/
// COPYRIGHT newbiely.com
// AUTHOR: newbiely
// This code is made available for public use without restriction.
// For complete instructions, tutorials, and further information, visit:
// https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
#include <ezButton.h>
#include "Arduino_RouterBridge.h"
#define KEY_NUM 4
#define PIN_KEY_1 3
#define PIN_KEY_2 2
#define PIN_KEY_3 5
#define PIN_KEY_4 4
ezButton keypad_1x4[KEY_NUM] = {
ezButton(PIN_KEY_1),
ezButton(PIN_KEY_2),
ezButton(PIN_KEY_3),
ezButton(PIN_KEY_4)
};
int last_key = 0;
String get_key(String arg) {
int key = last_key;
last_key = 0; // clear after reading
return String(key);
}
String get_status(String arg) {
if (last_key == 0)
return "No key pressed";
return "Last key: " + String(last_key);
}
void setup() {
Bridge.begin();
Monitor.begin();
for (byte i = 0; i < KEY_NUM; i++) {
keypad_1x4[i].setDebounceTime(100);
}
Bridge.provide("get_key", get_key);
Bridge.provide("get_status", get_status);
Monitor.println("Arduino UNO Q Keypad 1x4 Bridge ready");
}
void loop() {
for (byte i = 0; i < KEY_NUM; i++)
keypad_1x4[i].loop();
for (byte i = 0; i < KEY_NUM; i++) {
if (keypad_1x4[i].isPressed()) {
last_key = i + 1;
Monitor.println("Key pressed: " + String(last_key));
}
}
}
Python Code (Bridge)
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
*/
# COPYRIGHT newbiely.com
# AUTHOR: newbiely
# This code is made available for public use without restriction.
# For complete instructions, tutorials, and further information, visit:
# https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
from arduino.app_utils import *
import time
def loop():
result = Bridge.call("get_key")
key = int(result)
if key != 0:
print(f"Key pressed: {key}")
else:
print("No key pressed")
time.sleep(0.2)
App.run(user_loop=loop)
Detailed Instructions
- Connect: Wire the 1x4 keypad to the Arduino UNO Q as shown in the wiring diagram.
- Open Arduino App Lab: Launch Arduino App Lab and wait for the board to be detected.
- Create a new App: Click Create New App, name it Keypad1x4Bridge, then click Create.
- Paste the MCU sketch: Copy the MCU Bridge code above and paste it into sketch/sketch.ino.
- Paste the Python code: Copy the Python Bridge code above and paste it into the Python file in the App.
- Upload: Click the Run button in Arduino App Lab.
- Press keys on the keypad and watch the Python console.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q Keypad 1x4 Bridge ready
[2026-04-29 09:00:05] Key pressed: 1
[2026-04-29 09:00:09] Key pressed: 3
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:03] No key pressed
[2026-04-29 09:00:05] Key pressed: 1
[2026-04-29 09:00:07] No key pressed
[2026-04-29 09:00:09] Key pressed: 3
Telegram
Get Telegram notifications when a key is pressed on the 1x4 keypad — useful for remote doorbells, access codes, or event triggers.
MCU sketch: Keep the same MCU sketch from the previous Bridge section.
Python Code (Telegram)
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
*/
# COPYRIGHT newbiely.com
# AUTHOR: newbiely
# This code is made available for public use without restriction.
# For complete instructions, tutorials, and further information, visit:
# https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-keypad-1x4
from arduino.app_utils import *
import requests
import time
TELEGRAM_BOT_TOKEN = "YOUR_TELEGRAM_BOT_TOKEN"
CHAT_ID = "YOUR_CHAT_ID"
last_update_id = 0
def get_updates():
global last_update_id
url = f"https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/getUpdates"
params = {"offset": last_update_id + 1, "timeout": 5}
try:
response = requests.get(url, params=params, timeout=10)
data = response.json()
if data["ok"]:
return data["result"]
except Exception as e:
print(f"Error getting updates: {e}")
return []
def send_message(chat_id, text):
url = f"https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/sendMessage"
payload = {"chat_id": chat_id, "text": text}
try:
requests.post(url, data=payload, timeout=10)
except Exception as e:
print(f"Error sending message: {e}")
def loop():
global last_update_id
# Poll keypad and send Telegram alert on key press
result = Bridge.call("get_key")
key = int(result)
if key != 0:
msg = f"Key pressed: {key}"
print(msg)
send_message(CHAT_ID, msg)
# Also handle incoming Telegram commands
updates = get_updates()
for update in updates:
last_update_id = update["update_id"]
if "message" not in update:
continue
message = update["message"]
chat_id = message["chat"]["id"]
text = message.get("text", "").strip()
print(f"Received: {text}")
if text == "/start":
send_message(chat_id,
"Arduino UNO Q Keypad 1x4 Bot\n"
"/key - Read the last key pressed\n"
"/status - Get keypad status")
elif text == "/key":
result = Bridge.call("get_key")
key = int(result)
if key != 0:
send_message(chat_id, f"Key pressed: {key}")
else:
send_message(chat_id, "No key pressed")
elif text == "/status":
result = Bridge.call("get_status")
send_message(chat_id, result)
else:
send_message(chat_id, "Unknown command. Send /start for help.")
time.sleep(0.2)
App.run(user_loop=loop)
Detailed Instructions
- Replace YOUR_TELEGRAM_BOT_TOKEN with your actual bot token from BotFather.
- Replace YOUR_CHAT_ID with your Telegram chat ID.
- Paste this Python code into your App's Python file (keep the same MCU sketch).
- Click the Run button. Press keys on the keypad — your Telegram chat will receive alerts automatically.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:15:00] Waiting for Telegram messages...
[2026-04-29 09:15:08] Key pressed: 2
[2026-04-29 09:15:20] Received: /key
[2026-04-29 09:15:35] Key pressed: 4
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
Your bot has been created.
ArduinoBot
bot
OpenClaw
...OPENCLAW
OpenClaw support for Arduino UNO Q Keypad 1x4 is coming soon.
...OPENCLAW
Project Ideas
You can build many creative projects using the 1x4 keypad with Arduino UNO Q:
- Remote Access Code Entry: User presses a 4-key combination on the keypad; the MPU receives the sequence via Bridge and validates it, then sends a Telegram alert on success or failure
- Menu Navigation System: Use keys 1–4 to navigate a menu on the Serial Monitor or LCD display — MPU tracks the selection and takes action
- Event Buzzer System: Each key on the keypad triggers a different action (e.g., turn on a relay, sound a buzzer, or send a Telegram notification)
- Simple Game Controller: Use the 1x4 keypad as directional input (left/right/up/down) in a simple text-based game running on the Linux MPU
- Telegram Doorbell: Press key 1 on the keypad to ring a Telegram "doorbell" — the MPU sends a notification to the homeowner's phone automatically
Challenge Yourself
Ready to go further with the 1x4 keypad on Arduino UNO Q? Try these challenges:
- Easy: Modify the MCU sketch to light up an LED connected to D6 whenever any key is pressed.
- Medium: Implement a 4-digit PIN code system on the MCU — pressing keys 1-2-3-4 in sequence unlocks a relay, while any wrong sequence resets the input.
- Advanced: Build a Telegram-based remote keypad: use /key to query the last pressed key, then build a state machine in Python that interprets key sequences as commands (e.g., 1-1-2 = "lights on", 2-1-1 = "lights off").