Arduino UNO Q - Ultrasonic Sensor - LCD
This tutorial shows you how to use an Arduino UNO Q with an HC-SR04 ultrasonic sensor to measure distance and display it on an LCD I2C screen.
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .
Additionally, some of these links are for products from our own brand, DIYables .
Buy Note: Alternatively, you can assemble the LCD I2C display using LCD 1602 Display and PCF8574 I2C Adapter Module.
Overview of Ultrasonic Sensor and LCD
Learn about the ultrasonic sensor and LCD I2C in the tutorials below:
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
MCU Code
The Arduino UNO Q has two processors: the STM32 MCU (handles real-time hardware control) and the Qualcomm MPU (runs Debian Linux). In this section, only the STM32 MCU is programmed — the Linux side stays idle. A later section will show how both processors work together.
/*
* 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-ultrasonic-sensor-lcd
*/
#include <DIYables_LCD_I2C.h>
DIYables_LCD_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 columns, 2 rows
#define TRIG_PIN 4 // The Arduino UNO Q pin connected to the ultrasonic sensor's TRIG pin
#define ECHO_PIN 3 // The Arduino UNO Q pin connected to the ultrasonic sensor's ECHO pin
float duration_us, distance_cm;
void setup() {
lcd.init();
lcd.backlight();
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
}
void loop() {
// generate 10-microsecond pulse to TRIG pin
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
// measure duration of pulse from ECHO pin
duration_us = pulseIn(ECHO_PIN, HIGH);
// calculate the distance
distance_cm = 0.017 * duration_us;
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Distance: ");
lcd.print(distance_cm);
lcd.print(" cm");
delay(500);
}
※ NOTE THAT:
The I2C address for the LCD may differ by manufacturer. In this example we use 0x27 (the default for DIYables LCD modules).
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.
- Wire the components: Connect TRIG → pin 4, ECHO → pin 3. Connect LCD I2C to the I2C bus (SDA/SCL).
- Connect: Plug the Arduino UNO Q into your computer with a USB-C cable.
- Open Arduino App Lab: Launch Arduino App Lab and wait until it detects your Arduino UNO Q.
- Create a new App: Click the Create New App button.
- Give the App a name, for example: DIYables_UltrasonicLCD
- Click Create to confirm.
- You will see a set of folders and files generated inside your new App.
- 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 the 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 DIYables LCD I2C created by DIYables.io and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Search for Arduino_RouterBridge created by Arduino 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.
- Test: Wave your hand in front of the sensor — the distance should update on the LCD every 500 ms.
※ NOTE THAT:
- If nothing shows on the LCD, check: Troubleshooting LCD I2C
- This code is for learning. For production, apply the noise filter from Ultrasonic Sensor tutorial.
Linux + MCU Bridge Programming
The Arduino UNO Q has two processors that work together: the MPU (Qualcomm, runs Debian Linux) and the MCU (STM32, runs Zephyr OS with your Arduino sketch). They communicate using RPC via the Arduino_RouterBridge library — never via raw serial ports.
- The ultrasonic sensor and LCD are both connected to the MCU (STM32) — sensor on pins 2/3, LCD via I2C.
- The MPU cannot control these directly — it calls Bridge.call("read_distance") on the MCU, which measures distance, shows it on the LCD, and prints it to Monitor.
- The MPU has Wi-Fi — because the MPU runs full Debian Linux with Wi-Fi, it can receive Telegram commands and trigger readings remotely.
- Communication: Bridge.call() on the Linux side invokes Bridge.provide_safe() on the MCU side (since digitalWrite() and LCD writes are hardware APIs)
- ⚠️ Reserved: /dev/ttyHS1 (Linux) and Serial1 (MCU) are used by the Arduino Router — never open them directly
In short: MPU requests reading → MCU measures distance → MCU shows on LCD and prints to Monitor.
MCU sketch — ultrasonic sensor LCD display with 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-ultrasonic-sensor-lcd
*/
#include "Arduino_RouterBridge.h"
#include <DIYables_LCD_I2C.h>
DIYables_LCD_I2C lcd(0x27, 16, 2);
#define TRIG_PIN 2
#define ECHO_PIN 3
void read_distance() {
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
float duration_us = pulseIn(ECHO_PIN, HIGH);
float distance_cm = 0.017 * duration_us;
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Distance: ");
lcd.print(distance_cm);
lcd.print(" cm");
Monitor.print("Distance: ");
Monitor.print(distance_cm);
Monitor.println(" cm");
}
void setup() {
Bridge.begin();
Monitor.begin();
lcd.init();
lcd.backlight();
pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
Bridge.provide_safe("read_distance", read_distance);
Monitor.println("Ultrasonic Sensor LCD Bridge ready");
lcd.setCursor(0, 0);
lcd.print("Ready...");
}
void loop() {}
Python script (Arduino App Lab) — request distance reading from Linux every second:
/*
* 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-ultrasonic-sensor-lcd
*/
from arduino.app_utils import *
import time
def loop():
Bridge.call("read_distance")
time.sleep(1)
App.run(user_loop=loop)
- Note: Make sure Bridge.begin() is called in the MCU sketch and the sketch is uploaded before running the Python script on the Linux side.
- ⚠️ Warning: Never directly open /dev/ttyHS1 (on Linux) or use Serial1 (on MCU) in your code — these are reserved by the Arduino Router and accessing them will break the Bridge.
Detailed Instructions
- Upload the MCU sketch: Open Arduino App Lab, create a new App, paste the Bridge MCU sketch into sketch/sketch.ino, install the DIYables_LCD_I2C and Arduino_RouterBridge libraries, and click Run.
- Add the Python script: Paste the Python code above into the Python tab of the same App.
- Run the App: Click Run — Python requests a reading every second; MCU updates the LCD and Monitor.
- Check the console: Open the Console tab → MCU Monitor subtab to see the distance values.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
Ultrasonic Sensor LCD Bridge ready
Distance: 29.4 cm
Distance: 27.6 cm
Distance: 14.3 cm
Distance: 13.1 cm
Telegram Integration
Read the distance and display it on the LCD remotely via Telegram.
If you do not have a Telegram bot yet, see How to Create a Telegram Bot to get your bot token before continuing.
MCU sketch: Keep the same MCU sketch from the previous Bridge section — no changes needed. Make sure it is already uploaded and running on the STM32 before proceeding.
Python script (Arduino App Lab) — Telegram bot for ultrasonic LCD display:
/*
* 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-ultrasonic-sensor-lcd
*/
from arduino.app_utils import *
import requests
import time
BOT_TOKEN = "YOUR_BOT_TOKEN"
API_URL = f"https://api.telegram.org/bot{BOT_TOKEN}"
last_update_id = 0
def send_message(chat_id, text):
requests.post(f"{API_URL}/sendMessage", json={"chat_id": chat_id, "text": text})
def get_updates():
global last_update_id
resp = requests.get(f"{API_URL}/getUpdates", params={"offset": last_update_id + 1, "timeout": 5})
return resp.json().get("result", [])
def loop():
global last_update_id
updates = get_updates()
for update in updates:
last_update_id = update["update_id"]
msg = update.get("message", {})
chat_id = msg.get("chat", {}).get("id")
text = msg.get("text", "").strip()
if text == "/read":
distance = Bridge.call("read_distance")
send_message(chat_id, distance)
else:
send_message(chat_id, "Commands:\n/read — measure distance and display on LCD")
time.sleep(0.5)
App.run(user_loop=loop)
- Note: Replace YOUR_BOT_TOKEN with the token obtained from @BotFather on Telegram.
- Send /read to trigger a distance measurement — the result appears on the LCD and in Monitor.
Detailed Instructions
- Upload the MCU sketch: Use the Bridge MCU sketch from the previous section (upload it first if not already done).
- Paste the Telegram script: Copy the Python code above into the Python tab of your App in Arduino App Lab.
- Set your token: Replace YOUR_BOT_TOKEN in the script with your actual bot token.
- Run the App: Click Run — the bot starts listening for Telegram messages.
- Test it: Send /read — the bot replies with the measured distance, which also appears on the LCD.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 12:00:01] Telegram: /read
[2026-04-29 12:00:01] Distance: 29.4 cm
[2026-04-29 12:02:05] Telegram: /read
[2026-04-29 12:02:05] Distance: 13.1 cm
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
Your bot has been created.
ArduinoBot
bot
OpenClaw Integration
OpenClaw integration for Arduino UNO Q ultrasonic sensor with LCD is coming soon.
- Coming Soon: OpenClaw support for this project on Arduino UNO Q will be covered in a future update.
Application/Project Ideas
- Parking assistant display: Show "Safe", "Slow", "Stop" on LCD as a vehicle approaches a wall
- Water level display: Mount sensor above a tank — display the current level on LCD
- Visitor distance log: Display the closest approach distance on an LCD in a museum exhibit
- Smart measuring tool: Use sensor + LCD as a portable distance meter
- Object proximity display: Show real-time approach distance for a robotics project
Challenge Yourself
- Easy: Add a second line on the LCD — show "Close!" when distance < 20 cm, "Far" otherwise
- Medium: Display distance in both centimeters and inches on the two LCD lines
- Advanced: Send the actual distance value (in cm) directly back to the Telegram user as a message