Device selection for Modbus point to point link


I’m looking for a solution to wirelessly connect two or more Modbus RTU devices.
Here is the setup:

Remote device:
PLC controlled system
Has RS485 and ethernet ports available

Main device:
PC to log data from and control the remote device
USB and ethernet ports available

Possibility of adding a second similar remote node in the future.

I need to receive measurement values from and send control messages to the remote device. My current plan is to use Modbus RTU from the PLC to the main PC. I believe the NCD RS485 modems in AutoEncoder mode would work for this. In that case I would use a RS485 to USB adapter to connect the receiver modem to the PC.


  1. What is the difference of these two devices in my use case? Are they interchangeable?

  2. I would prefer an ethernet connection over USB at the main device. Would it be possible to interface to this wireless RS485 network using the “Industrial IoT Wireless to Ethernet Modem”

  3. Instead of using RS485 and Modbus RTU, would it be possible to use two of “Industrial IoT Wireless to Ethernet Modem” to directly send TCP/IP communications between the devices?

These devices look very flexible so I’m trying to find the best configuration for us.
Thanks for the help!


  1. The RS485 to Wireless converter would the the device to use for your application. I would not recommend the RS485 modem, that is intended for receiving data from our wireless sensors, then feeding that data to a computer via RS 485.

  2. Yes, you can use the Ethernet Modem.

  3. That is certainly possible. It’s not a typical use case but I see no reason it would not work. Basically any data received over the TCP socket is transmitted out wirelessly and any data received wirelessly is transmitted out the TCP socket. Using the devices like this would essentially give you a long range wireless TCP socket.

Hi Travis!

This sounds great!
Sounds like these devices will work perfectly for my use case so I’ll order some for testing.

Thank you!