Hello.

I am working with an Modbus slave electrical meter in which the manufacturer implemented a non-standard modbus function code (Electro Industries Nexus 1262, Modbus function code 23h). The only available meter communication port is 2 wire RS-485, serial Modbus RTU. I need to convert this to Ethernet Modbus TCP, and communicate to it with the custom function code. I have tried a Ruggedcom and a Moxa RTU to TCP converter, but they just reject the any packets with the custom function code request. Does anyone have an converter product that will pass a non-standard function code?

Thanks for your help.

 

> I have tried a Ruggedcom and a Moxa RTU to TCP converter, but they just reject the any
> packets with the custom function code request.

That's odd, as custom functions are trivial to handle as long as they respect the max length limitations and CRC form of Modbus/RTU.

The Digi and Lantronix products don't mind custom functions codes, but your timing could change because they use smart size-estimation for known functions, but always use the character timeout for unknown functions.

Are you sure the problem with rugged & moxa is not just timing related? try adjust the character/end-of-message-detect time out.

 

Hi there,

HMS has a gateway were almost any serial protocol can easely be implemented.

The gateway has a serial interface where standard modbus commands can be used (selected), but also non-standard commands can be implemented, if you know the structure of the telegram.
Link to product:

http://www.anybus.com/support/support.asp?PID=493&ProductType=Anybus Communicator

My 2 cents

//Patrick Lansdorf