When comparing RS232 vs RS485, it’s essential to understand that both are serial communication standards — meaning they send data bit by bit over a single communication line.
However, RS232 is designed for short, point-to-point connections, while RS485 supports long-distance, multi-device networks using differential signaling.
This guide explains the key differences, pin configurations, wiring, and real-world use cases of both RS232 and RS485 to help you choose the right one for your system.
Table of Contents
What Is RS232?
RS232 (Recommended Standard 232) is a serial communication protocol originally developed for connecting computers and modems. It uses single-ended signaling, meaning it transmits data through one wire referenced to ground.
Key Features of RS232
- Signal Type: Single-ended (one signal wire + ground)
- Number of Devices: 1 transmitter and 1 receiver (point-to-point)
- Maximum Cable Length: Typically up to 15 meters (50 feet)
- Data Transmission Speed: Up to 115.2 kbps
- Voltage Levels: ±3V to ±15V
- Typical Connectors: DB9 or DB25
RS232 is simple, reliable, and ideal for short-distance communication between two devices — like a PC and a serial device.
RS232 Pinout and Wiring Explained
RS232 DB9 Pinout (Most Common)
| Pin | Signal Name | Direction | Description |
|---|---|---|---|
| 1 | DCD | Input | Data Carrier Detect |
| 2 | RXD | Input | Receive Data |
| 3 | TXD | Output | Transmit Data |
| 4 | DTR | Output | Data Terminal Ready |
| 5 | GND | — | Signal Ground |
| 6 | DSR | Input | Data Set Ready |
| 7 | RTS | Output | Request to Send |
| 8 | CTS | Input | Clear to Send |
| 9 | RI | Input | Ring Indicator |
RS232 DB25 Pinout (Older Standard)
| Pin | Signal | Direction | Description |
|---|---|---|---|
| 2 | TXD | Output | Transmit Data |
| 3 | RXD | Input | Receive Data |
| 4 | RTS | Output | Request to Send |
| 5 | CTS | Input | Clear to Send |
| 6 | DSR | Input | Data Set Ready |
| 7 | GND | — | Signal Ground |
| 8 | DCD | Input | Data Carrier Detect |
| 20 | DTR | Output | Data Terminal Ready |
| 22 | RI | Input | Ring Indicator |
💡 Tip: For most modern RS232 devices, only TXD, RXD, and GND are required for basic data transmission.
What Is RS485?
RS485 (Recommended Standard 485) is a more advanced serial communication standard that supports differential signaling, making it suitable for long-distance and multi-device networks.
Key Features of RS485
- Signal Type: Differential (two signal wires — A and B)
- Number of Devices: Up to 32 transmitters and 32 receivers on a single bus
- Maximum Cable Length: Up to 1200 meters (4000 feet)
- Data Transmission Speed: Up to 10 Mbps (at shorter distances)
- Voltage Levels: -7V to +12V
- Typical Connectors: Often terminal blocks or RJ45
RS485 is commonly used in industrial automation and embedded systems due to its robustness and ability to handle noise over long distances.
RS485 Pinout and Wiring Explained
Unlike RS232, RS485 doesn’t use a standardized connector like DB9 or DB25. Instead, it uses differential pairs and sometimes a ground reference.
RS485 Typical 2-Wire Pinout (Half Duplex)
| Pin | Signal | Description |
|---|---|---|
| 1 | A (–) | Inverting signal line |
| 2 | B (+) | Non-inverting signal line |
| 3 | GND | Signal ground (optional) |
- Half-duplex mode: Devices share the same wire pair for transmitting and receiving.
- Twisted pair cables are recommended to reduce electromagnetic interference.
RS485 4-Wire Pinout (Full Duplex)
| Pin | Signal | Description |
|---|---|---|
| 1 | TX+ | Transmit positive |
| 2 | TX– | Transmit negative |
| 3 | RX+ | Receive positive |
| 4 | RX– | Receive negative |
| 5 | GND | Signal ground (optional) |
💡 Tip: Always use 120Ω termination resistors at both ends of an RS485 bus to prevent signal reflection and maintain data integrity.
Want to wire RS485 correctly for maximum performance?
👉 Check out our full guide on RS-485 Wiring Guidelines
RS232 vs RS485 Wiring Example
RS232 Simple Wiring
Device 1 (TXD) → Device 2 (RXD)
Device 1 (RXD) ← Device 2 (TXD)
Device 1 (GND) ↔ Device 2 (GND)RS485 Differential Wiring
All Devices Share the Same Bus:
A(–) ↔ A(–)
B(+) ↔ B(+)
Optional: GND ↔ GNDRS485’s differential pair (A/B) allows many devices to share the same bus without interference — one of its biggest advantages over RS232.
RS232 vs RS485: Technical Comparison Table
| Feature | RS232 | RS485 |
|---|---|---|
| Signal Type | Single-ended | Differential |
| Communication | Point-to-point | Multi-point |
| Max Devices | 2 | 64 (32 Tx + 32 Rx) |
| Max Distance | 15 m (50 ft) | 1200 m (4000 ft) |
| Speed | 115.2 kbps | Up to 10 Mbps |
| Noise Immunity | Low | High |
| Common Connectors | DB9, DB25, RJ45 | Terminal block, RJ45 |
| Typical Use | PC-to-device | Industrial automation, Modbus |
| Wiring | Simple (TX, RX, GND) | Twisted pair (A, B, GND) |
Which Is Better: RS232 vs RS485?
Choosing between RS232 vs RS485 depends on your application requirements:
- ✅ Choose RS232 if:
- You need simple, direct communication between two devices.
- The distance is short (under 15 meters).
- There’s minimal electrical noise in the environment.
- ✅ Choose RS485 if:
- You need to connect multiple devices on the same bus.
- The communication distance exceeds 15 meters.
- The environment is electrically noisy (industrial or outdoor).
In industrial automation, RS485 is generally preferred due to its robustness and scalability.
Advantages of RS485 vs RS232
- Longer communication distance — up to 4000 feet.
- Better noise resistance due to differential signaling.
- Supports multiple devices on a single network.
- Higher data rates at shorter distances.
- Ideal for industrial and automation environments.
When RS232 Is Still Useful
While RS485 is more advanced, RS232 is still widely used in:
- Legacy systems (older computers or lab instruments)
- Debugging serial devices
- Simple device-to-device links
RS232’s simplicity makes it perfect for applications where only two devices are involved and wiring complexity must be minimized.
Practical Example: RS232 vs RS485 in Real Applications
| Industry | Common Use Case | Recommended Standard |
|---|---|---|
| Industrial Automation | Connecting multiple Sensors to one PLC | RS485 |
| Laboratory Equipment | Single instrument communication | RS232 |
| PC Peripheral Connection | Serial mouse, modem, Printer | RS232 |
| Embedded Systems | Multi-sensor network | RS485 |
How to Convert Serial to Ethernet
In modern systems, serial ports (RS232 or RS485) are often replaced or extended with Ethernet-based communication. This is done using a Serial-to-Ethernet Converter (also known as a Serial Device Server).
What Is a Serial-to-Ethernet Converter?
It’s a hardware device that converts RS232, RS422, or RS485 serial data into TCP/IP packets that can be sent over a standard Ethernet network.
How It Works
- Serial Device → Converter: The serial data from your RS232 or RS485 device enters the converter.
- Converter → Network: The converter wraps the serial data into TCP/IP packets.
- Network → Remote System: A remote PC or server receives the data over Ethernet and communicates as if it were directly connected via serial.
Common Use Cases
- Remote monitoring of PLCs or sensors
- Integrating legacy serial devices into modern LAN networks
- Industrial automation and building management systems
- IoT gateways and remote device management
Top Devices for Serial-to-Ethernet Conversion
| Device | Supported Protocols | Description |
|---|---|---|
| USR-TCP232-410s | RS232 / RS485 to TCP/IP | Compact and cost-effective converter supporting both RS232 and RS485 interfaces for Ethernet networking. |
| Moxa NPort Series | RS232 / RS422 / RS485 to TCP/IP | Industrial-grade serial device servers used for reliable Modbus and serial data transmission over LANs. |
| Digi ConnectPort | RS232 / RS485 to TCP/IP | Enterprise-grade gateway that converts legacy serial protocols like Modbus RTU to Modbus TCP/IP for modern SCADA and IoT systems. |
Use Case Example
These devices are widely used to convert Modbus RTU (serial) into Modbus TCP/IP, allowing industrial controllers, PLCs, and sensors to communicate seamlessly over Ethernet networks.
By bridging legacy serial communication with IP-based infrastructure, they make it possible to:
- Monitor industrial equipment remotely
- Integrate older Modbus systems into cloud-based dashboards
- Reduce cabling complexity and improve scalability
FAQs About RS232 and RS485
Can RS232 and RS485 be directly connected?
No. They use different voltage levels and signaling methods. You’ll need an RS232-to-RS485 converter.
What cable should I use for RS485?
Use twisted pair shielded cable (Cat5e or industrial-grade twisted pair) to minimize noise and maintain signal integrity.
How do I identify A and B lines in RS485?
A (–) is typically the non-inverting line
B (+) is the inverting line
(Some manufacturers swap these labels — always check datasheets.)
Conclusion: RS232 vs RS485 — Which Should You Choose?
- Use RS232 for short, simple, point-to-point links.
- Use RS485 for long-distance, multi-device, industrial communication.
In modern systems, RS485 is preferred for its speed, distance, and noise immunity, but RS232 remains valuable for legacy or single-device applications.