An RS485 to Ethernet converter does one thing: it takes data from your serial device and puts it on the network. Simple idea. But the first time you try to set one up, it’s never quite as simple as it looks.
Default IP addresses. Serial parameters that have to match exactly. TCP Server vs. TCP Client. It’s easy to spend an hour and end up with nothing.
This guide covers what actually works—step by step, with the things you actually need to know.
Before You Start: What You’ll Need
- RS485 to Ethernet converter (this guide uses Valtoris 1CH-RS485-ETH as an example)
- RS485 device (PLC, sensor, meter) with known serial parameters
- Ethernet cable
- 24V DC power supply (most industrial panels have 24V)
- Computer on the same network
- Device manual for your RS485 equipment (to get baud rate, parity, etc.)
One thing to know: The most common problem is mismatched serial settings. Write down your device’s parameters before you start.
Step 1: Hardware Connection
RS485 Wiring
RS485 uses two wires, usually labeled A and B (or Data+ and Data-). Some installations also use a ground (GND) wire for longer distances.
Wiring rules:
- A to A
- B to B
- GND to GND (if used)
If you have multiple devices on the same RS485 bus, they connect in a daisy chain. The last device on the chain may need a 120Ω termination resistor across A and B.
**RS485 supports cable runs up to 1200 meters at lower baud rates—far beyond RS232’s 15-meter limit.
Ethernet and Power
Plug an Ethernet cable into the converter and connect it to your network switch or directly to your computer.
Apply 9-24V DC power. In industrial panels, 24V is standard. The power LED should light up.
Step 2: Find the Converter on Your Network
New converters have either a default IP address or use DHCP.
Check the manual for the default IP. Common defaults: 192.168.1.100, 192.168.0.7, or 192.168.2.1.
If you do not see a default Internet Protocol address listed the converter probably uses Dynamic Host Configuration Protocol. You should connect the converter to your network. Then check the list of Dynamic Host Configuration Protocol clients on your router. Look for a device that has the Media Access Control address as the converter, which is usually on a sticker.
You can use a special tool to find the converter. A lot of companies that make converters give you a program, for Windows that can find converters on your network. For example Valtoris gives you a program called VirCom. You can run this program. Then click on the button that says “Search”. This program will show you a list of all the converters it can find and their Internet Protocol addresses.
Once you have the IP, open a browser and type it in. You should see the converter’s configuration page.
If you can’t get to the page:
- Make sure your computer is on the same subnet (e.g., if converter is 192.168.1.100, your computer should be 192.168.1.x)
- Temporarily disable your firewall
- Try a different browser
Step 3: Configure Network Settings
Once you’re in the configuration page, go to network settings.
| Setting | Recommendation | Why |
|---|---|---|
| IP address | Static | DHCP can change later, breaking your connection |
| Subnet mask | 255.255.255.0 | Standard for small networks |
| Gateway | Your router’s IP | Needed for access from other subnets |
| DNS | Optional | Only needed if using domain names |
Write down the IP you assign. You’ll need it later.
Step 4: Configure Serial Port Settings
This is where most problems happen. Every setting here must match your RS485 device exactly.
| Parameter | Typical Values | Your Device Setting |
|---|---|---|
| Baud rate | 9600, 19200, 38400, 115200 | __________ |
| Data bits | 7, 8 | __________ |
| Parity | None, Even, Odd | __________ |
| Stop bits | 1, 2 | __________ |
| Flow control | None, RTS/CTS, XON/XOFF | __________ |
Where to find these values:
- Check your device’s manual
- Look at existing configuration if it’s already working
- Defaults are often 9600, 8, N, 1 for Modbus RTU devices
If these don’t match your device exactly, you’ll get no data or garbage data. No exceptions. The converter can’t guess.
Step 5: Choose the Operating Mode
This tells the converter how to handle the connection.
(Table: Operating Mode Comparison)
| Mode | Who Initiates | Connection Type | Best For |
|---|---|---|---|
| TCP Server | Computer connects to converter | Persistent | One computer polling one device |
| TCP Client | Converter connects to computer | Persistent | Converter pushing data to fixed IP |
| UDP | No connection | Connectionless | Broadcast, multiple receivers |
When it comes to the converter the TCP Server is usually the way to go. To get started you need to set the converter to TCP Server mode. Then you have to pick a port number. A lot of people use 4001. If you are working with Modbus you should use 502. Once you have done that you just need to save the settings for the Server. The TCP Server needs to be set up so make sure you save the settings, for the TCP Server.
The converter is now listening on that port, waiting for a connection.
Step 6: Test the Connection
Quick test with free tools: Download a TCP test utility like Hercules, PuTTY (in raw mode), or Tera Term. Connect to the converter’s IP and port. Send a few bytes your device should respond to.
If you get a response, you’re done with the basic configuration.
If not:
Step 7: Troubleshooting When Nothing Works
| Symptom | Likely Cause | Try This |
|---|---|---|
| Can’t ping converter | Wrong IP or subnet | Check both IPs, adjust one |
| Ping works, connection fails | Firewall | Disable firewall temporarily |
| Connect but no data | Wiring wrong | Swap A and B |
| Data is garbage | Baud rate wrong | Check device settings |
| Data intermittent | Ground loop or interference | Check GND connection, use shielded cable |
| One device works, another doesn’t | Address conflict | Check Modbus slave IDs |
People often get A/B wiring wrong it is the common mistake. The thing with RS485 is that it is very particular, about which wire goes where. If you are not getting any data you should try swapping the two wires at one end of the RS485 connection and see what happens. Do not worry it will not hurt the RS485 or anything else.
Step 8: Advanced Configuration (Optional)
Virtual COM Port (VCOM)
If your software expects a COM port and doesn’t speak TCP/IP directly, you need virtual COM software.
Install the software (Valtoris provides VirCom). Create a new virtual COM port (say, COM5) and map it to the converter’s IP address and port number. Your software opens COM5, and the driver handles the network communication.
Modbus Gateway
If your RS485 device uses Modbus RTU, many converters can act as Modbus gateways.
The converter does something cool in this mode. It waits for connections from Modbus TCP on port 502. When it gets a request the converter changes it into Modbus RTU. Then sends it out through the serial port. The converter then gets the response. Changes it back, into Modbus TCP. This is what the converter does with Modbus TCP and Modbus RTU.
No virtual COM port needed. Just point your SCADA to the converter’s IP address.
Heartbeat and Keep-Alive
For wireless or unstable connections, some converters support heartbeat packets or keep-alive mechanisms. These ensure the connection stays alive and can trigger automatic reconnection if it drops.
Real-World Example: Solar Farm Monitoring
A photovoltaic plant in Northern China needed to collect data from 200 inverters spread across 2 square kilometers. Each inverter had an RS485 port. Running individual cables was impossible.
They installed RS485 to Ethernet converters at each inverter cluster, configured each with a static IP, and set them to TCP Server mode. A central server polled each converter every second.
Result: Data collection cycle dropped from 5 minutes to under 1 second. System efficiency improved by 27% due to faster fault detection.
Summary
| Step | What to Do | Key Point |
|---|---|---|
| 1 | Wire A to A, B to B | Check polarity |
| 2 | Find converter IP | Use discovery tool or check router |
| 3 | Set static IP | Avoids future connection loss |
| 4 | Match serial settings | Must match your device exactly |
| 5 | Choose TCP Server mode | Most common, simplest |
| 6 | Test with utility | Hercules, PuTTY, or Tera Term |
| 7 | Troubleshoot | Start with A/B swap |
The Valtoris 1CH-RS485-ETH follows the same steps shown here. It adds -40°C to 85°C operation, 9-24V DC power, DIN rail mounting, and 2KV surge protection.
Regardless of brand, the process is the same. Match the wires. Match the settings. Pick the right mode. Test.
