Arduino UNO Q RS232
Use RS232 serial communication with the Arduino UNO Q and a TTL-to-RS232 module. The MCU communicates over SoftwareSerial, the module converts TTL signals to RS232 voltage levels for long-distance serial communication. With Bridge and Telegram, you can send and receive RS232 data remotely from Python or your phone.
In this tutorial, you will learn:
- How RS232 communication works and why a TTL-to-RS232 module is needed
- How to wire the TTL-to-RS232 module to the Arduino UNO Q
- How to send and receive data over RS232 on Arduino UNO Q
- How to use Bridge to control RS232 communication from Python on Arduino UNO Q
- How to send and receive RS232 data via Telegram on Arduino UNO Q
- How to use OpenClaw on Arduino UNO Q with RS232
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 TTL to RS232 Module
The Arduino UNO Q MCU communicates over UART using TTL logic levels (3.3V). TTL signals travel only short distances. To communicate over longer distances with RS232-compatible devices (PLCs, older computers, industrial equipment), you need to convert the TTL signal to RS232 voltage levels (typically ±12V). The TTL-to-RS232 module performs this conversion in both directions.
Pinout
- TTL interface (connects to Arduino UNO Q MCU):
- VCC: Power input — connect to 3.3V
- GND: Ground
- RXD: Data input — connect to MCU TX pin (D6)
- TXD: Data output — connect to MCU RX pin (D7)
- RS232 interface: DB9 female D-Sub connector — connect to your RS232 device
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
| TTL-to-RS232 Module Pin | Arduino UNO Q MCU Pin | Note |
|---|---|---|
| VCC | 3.3V | |
| GND | GND | |
| RXD | D6 (MCU TX) | |
| TXD | D7 (MCU RX) |
Connect the DB9 connector to your RS232 device or RS232-to-USB cable.
How To Program For RS232
- Include SoftwareSerial and create an RS232 serial object:
#include <SoftwareSerial.h>
SoftwareSerial rs232(7, 6); // RX: D7, TX: D6
- Read incoming RS232 data:
if (rs232.available()) {
char data = rs232.read();
}
- Send data over RS232:
rs232.print("Hello from Arduino UNO Q");
rs232.println("With newline");
Arduino UNO Q Code
/*
* 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-rs232
*/
// 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-rs232
#include <SoftwareSerial.h>
SoftwareSerial rs232(7, 6); // RX: D7, TX: D6
void setup() {
Monitor.begin(9600); // USB serial for debug output
rs232.begin(9600); // RS232 module serial
delay(100);
}
void loop() {
// Forward data from RS232 to Monitor
if (rs232.available()) {
char data = rs232.read();
Monitor.print(data);
rs232.print(data); // echo back to sender
}
// Forward data from Monitor to RS232
if (Monitor.available()) {
char data = Monitor.read();
rs232.print(data);
}
}
Detailed Instructions
First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial before proceeding.
- Connect: Wire the TTL-to-RS232 module to the Arduino UNO Q MCU as shown in the wiring diagram.
- 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: RS232
- Click Create to confirm.
- Paste the sketch: Copy the MCU code above and paste it into sketch/sketch.ino.
- Upload: Click the Run button in Arduino App Lab.
Testing
To test RS232 communication:
- Connect the DB9 port of the module to your PC using an RS232-to-USB cable:
- Set the baud rate to 9600, select the correct COM port.
- Type any text and send it. The Arduino UNO Q will echo it back — you should see the echoed data in the terminal.
Bridge: Linux + MCU
This section shows how to send and receive RS232 data from the Linux side (Python) via Bridge:
- The TTL-to-RS232 module is connected to the MCU via SoftwareSerial — the MCU handles all serial I/O
- The MPU cannot use SoftwareSerial directly — it calls Bridge functions to send/receive RS232 data
- The MPU has Wi-Fi — running full Debian Linux, it can relay RS232 data to Telegram or web services
- 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
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-rs232
*/
// 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-rs232
#include "Arduino_RouterBridge.h"
#include <SoftwareSerial.h>
SoftwareSerial rs232(7, 6); // RX: D7, TX: D6
String received_data = "";
String send_rs232(String arg) {
rs232.println(arg);
Monitor.print("Sent via RS232: ");
Monitor.println(arg);
return "ok:sent";
}
String get_received(String arg) {
String result = received_data;
received_data = "";
return result;
}
void setup() {
Bridge.begin();
Monitor.begin();
rs232.begin(9600);
delay(100);
Bridge.provide_safe("send_rs232", send_rs232);
Bridge.provide("get_received", get_received);
Monitor.println("Arduino UNO Q RS232 Bridge ready");
}
void loop() {
// Accumulate incoming RS232 data between Bridge calls
while (rs232.available()) {
char c = rs232.read();
received_data += c;
}
}
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-rs232
*/
# 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-rs232
from arduino.app_utils import *
import time
def loop():
print("Sending message via RS232...")
result = Bridge.call("send_rs232", "Hello from Arduino UNO Q!")
print(f"Result: {result}")
time.sleep(1)
data = Bridge.call("get_received")
if data:
print(f"Received via RS232: {data}")
else:
print("No data received")
time.sleep(2)
App.run(user_loop=loop)
Detailed Instructions
- Connect: Wire the TTL-to-RS232 module to the Arduino UNO Q as shown above.
- Open Arduino App Lab and create a new App named RS232Bridge.
- Paste the MCU sketch into sketch/sketch.ino.
- Paste the Python code into the Python file.
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- 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. Python will send a message via RS232 and read back any echoed data.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:01] Arduino UNO Q RS232 Bridge ready
[2026-04-29 09:00:06] Sent via RS232: Hello from Arduino UNO Q!
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:00:06] Sending message via RS232...
[2026-04-29 09:00:06] Result: ok:sent
[2026-04-29 09:00:07] Received via RS232: Hello from Arduino UNO Q!
Telegram
Send and receive RS232 data through Telegram — forward messages from industrial devices to your phone or send commands from Telegram to an RS232 device.
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-rs232
*/
# 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-rs232
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():
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 RS232 Bot\n"
"/send <message> - Send a message via RS232\n"
"/read - Read data received from RS232")
elif text.startswith("/send"):
parts = text.split(" ", 1)
if len(parts) < 2:
send_message(chat_id, "Usage: /send <message>")
else:
result = Bridge.call("send_rs232", parts[1])
send_message(chat_id, f"Sent via RS232: {parts[1]}")
elif text == "/read":
data = Bridge.call("get_received")
if data:
send_message(chat_id, f"Received via RS232:\n{data}")
else:
send_message(chat_id, "No data received yet.")
else:
send_message(chat_id, "Unknown command. Send /start for help.")
time.sleep(0.3)
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 the Python code into your App's Python file (keep the same MCU sketch).
- Click the Run button — send /send Hello in Telegram to transmit data over RS232.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 09:10:05] Received: /send Hello RS232 device!
[2026-04-29 09:10:09] Received: /read
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 RS232 is coming soon.
...OPENCLAW
Project Ideas
You can build many useful projects with RS232 communication and Arduino UNO Q:
- Industrial PLC Gateway: Connect the Arduino UNO Q to a PLC or industrial controller via RS232; Python forwards received status messages to Telegram so you can monitor factory equipment from your phone
- Barcode Scanner Integration: Connect an RS232 barcode scanner to the TTL-to-RS232 module; when a barcode is scanned, the MCU reads the data via SoftwareSerial and Python sends it to Telegram for logging
- Legacy Serial Printer Control: Send print commands from Telegram through Bridge to the MCU, which forwards them over RS232 to a legacy serial printer or display terminal — bridging modern wireless control with older serial hardware
- GPS with RS232 Output: Connect an RS232-output GPS receiver to the module; the MCU reads NMEA sentences, Python parses the data, and Telegram sends location updates on demand
- Remote Serial Diagnostics: Forward RS232 debug output from an embedded device to Telegram via Bridge — useful for monitoring remote devices without needing physical access to a serial terminal
Challenge Yourself
Ready to go further with RS232 on Arduino UNO Q? Try these challenges:
- Easy: Modify the MCU sketch to accumulate received bytes until a newline character is detected, then expose the complete line as a single string via get_received — preventing partial reads when data arrives in chunks.
- Medium: Build a bidirectional relay: Python reads temperature from a sensor Bridge function and formats a status string, sends it via send_rs232 every 30 seconds, and simultaneously reads any RS232 responses with get_received — forwarding them as Telegram notifications.
- Advanced: Implement a message queue: Python maintains a list of outgoing RS232 messages, sends them one per second via send_rs232, and collects all responses with get_received; after each batch, it sends a Telegram summary showing how many messages were sent and what responses were received.