Wireless Modbus TCP

Products
1

Hi all,

We have an upcoming install where a remote device is located too far from our main installation to run a direct Ethernet cable. The remote device supports Modbus TCP (Ethernet only — no RS-485/RTU).

We’re using the NCD Enterprise Gateway, which has the built-in DigiMesh 900 MHz module. Since DigiMesh is an open standard, I’m wondering if there’s a way to bring the remote Modbus TCP data in through that same receiver rather than adding a separate network path.

Specifically — is there an NCD node or any DigiMesh-compatible device that could poll a Modbus TCP device locally and transmit that data back through the DigiMesh mesh network to the enterprise gateway?

Thanks in advance!

2

We have implemented a similar solution in the past. While it may not be the most aesthetically pleasing option, it is functional.

I just conducted a quick test to replicate your setup.

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You will need the following hardware:
Industrial IoT Wireless Ethernet Modem

Here are the steps to follow:

  1. Open the lid and set the jumpers to USB.
  2. Connect to XCTU.
  3. Set the destination address to your gateway.
  4. Change the mode to AT mode.
  5. Switch the jumpers back to ETH.

You will send data to this modem using the gateway. We have a flow you can use to get started. The modem will receive the Digi payload and transmit it over Ethernet. The Ethernet will then communicate with the slave device via TCP/IP. The slave will respond, and the data will return to the gateway through Digi.

3

Hey @Bhaskar,

Thank you for the response. This is really interesting. So if I’m understanding correctly, the gateway is polling the Modbus device?

How frequently is the gateway polling the slave?

4

correct. gateway will send the modbus command and device will respond. the minim polling interval will be 3 sec

5

Hey @Bhaskar,

I have installed the modem like you prescribed above. When I set the jumpers to USB, do I connect XCTU to the device via the ethernet port still? There is no USB port on the modem so I’m confused on how to connect it to XCTU. Do I need to get a serial to USB cable to connect directly to the XBee chip? Any help you can provide would be greatly appreciated.

Thank you!

6

Hello @gnelson You should use the USB port to communicate with XCTU and perform the settings as Bhaskar mentioned. It should be a USB port under Ethernet port on your Ethernet Modem.

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Could you share a picture of your ethernet modem please?
Thanks.