Encapsulated Modbus RTU

#1

Hi I need a little help, I have a device which outputs Modbus over RS 485. I use a Modbus to Ethernet converter which encapsulates the Modbus data into an Ethernet packet.
I use the amassing node-red-contrib-modbus nodes. However I struggle to make any progress to de-capsulate the packets. Is this possible with this nodes?

Thank you for your help

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#2

You don't mention what hardware you are using, but I have had success using the RS485 and node-red-contrib-modbus directly with a USB to RS485 adapter on a Raspberry Pi, the converter would not be needed. The key issue is to understand the modbus registers the device outputs.

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#3

I'm using a USR-TCP232-304 RS485 Eternet converter. This device encapsulates the Modbus 485 signal from the PLC i'm using into a TCP packet. There is a difference between devices which naively support Modbus TCP and these converts. I use SCADA BR (now SCADA LTS) and can read the Modbus from the PLC fine via TCP. This application has an option 'ENCAPSULATED'.

Here is a discussion but I don't understand the bit with 'added to the main branch'
https://github.com/stephane/libmodbus/issues/192

Thanks for helping out.

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