Hex to ModBus TCP Field Device

K

Thread Starter

Karen

We are currently converting a current loop signal to serial. It reads/writes in Hex. Is there anyway to take this serial hex data and convert it to ModBus TCP? The device the source is coming from is not ModBus RTU or ASCII.

Thank you for your time.
 
"Hex" is ASCII. The number base of the ASCII characters in hex notation is ASCII 0 through ASCII F. Modbus ASCII is an example of a hex protocol over a serial communication medium.

It sounds like the wrapper and payload organization of the device you are trying to talk doesn't comply with Modbus ASCII though. It's still worth reading the docs on Modbus ASCII to get a handle on how a hex protocol works.

Digi sells a box called the DigiOne IAP. Modbus/TCP is already handled by this box. It also allows you to add a user program for a generic ASCII (hex) protocol. I haven't used it in this capacity, but it's worth taking a look at.
 
Thanks for your response!

Let me explain exactly what we are trying to do and maybe you can better direct me in the right direction :).

We have a field device that runs on current loops. We are trying to make these devices point to point and integrate them into a DCS type system.

So we take the current loop signal and convert it to a serial signal. From the serial signal we are connected into the Digi One IAP (port 2) and configured it to use ASCII Import on the DB9 side and MODBUS TCP on the ethernet side. From our DCS platform we can connect to the Modbus side but are having issues with sending/receiving data from the field device.

Before we were taking the serial signal and converting it directly to TCP/IP. To test this I used TCP Port Toolkit and sent the poll request as "HEX". The ASCII of what we send looks similar to . We get the correct responses back (reading the ASCII response as hex values) that we expected.

Anyway I know our end device doesn’t use a ModBus protocol. We are looking to convert it to a ModBus protocol so we can import it as a SCADA point. Any suggestions?

Again thanks for your time!

Karen
 
Can you explain this a bit better? Are any of the devices you are using programmable (and therefore can do some protocol conversion), or are you looking for a device that can read a 4-20mA signal and be able to send out Modbus/TCP? I would opt for getting a Modbus/TCP device that can read analog inputs (4-20mA if that is your case) and be polled from a modbus master. It is probably simpler and cleaner than multiple devices with protocol conversion.

KEJR
 
J

Jerry Miille

I really do not understand your needs, but, we offer a protocol converter that "might" provide a solution to your problem. You can contact me at jmiile "at" miille.com if you have more questions. Thanks,

Jerry Miille

Miille Applied Research Co., Inc.
http://www.miille.com/
 
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