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) |
Jumper wires are good for a quick test, but not for a final build. To do that, mount a Proto Screw Terminal Block Shield or a Screw Shield V2 on the Arduino UNO Q. Below is the wiring diagram with the Screw Shield V2.
This image is created using Fritzing. Click to enlarge image
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
*/
#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
*/
#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 script was developed by newbiely.com
This Arduino UNO Q script 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
"""
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 script was developed by newbiely.com
This Arduino UNO Q script 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
"""
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
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
You can adapt the OpenClaw to this tutorial by refering the instruction on Arduino Uno Q - OpenClaw Tutorial
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.