Lantronix Ethernet to RS485

Just curious if anyone has used Lantronix to do this?
How can I test this if it is actually working (ie loop back test)? I am using it for Modbus.


Is there a reason you want to use this instead of a proper Modbus gateway?

Hi Kevin.
Thanks for the response. Yes, client has it, several of it and it is a requirement that it goes from TCPIP to RTU.

I assume this is just a “dumb” ethernet-to-serial converter.

The Modbus RTU over TCP driver should work, but RTU over TCP is a terrible and unreliable protocol, so using a real Modbus TCP gateway is significantly more reliable.

What do you recommend that is less than $120?

I’ve always recommended the Moxa MGate to people but I think they are more like $200-$220.

Maybe someone else can chime in with other suggestions.

We use either MGates or Digi One IAPs. We have had luck with both.

What is the difference between tcpip/RS485 converter and a “real Modbus TCP gateway”?

Modbus on a serial line is different from Modbus TCP – different framing, escaping, and error checking. TCP/IP has its own error checking and guarantee of in-order, no missing byte delivery, so it can be simpler. A “real” gateway understands both protocols, unpacking requests on one port and re-packing into the other format for the other port. In both directions.

To add to this, when you just dump an RTU frame into a TCP-to-serial converter you have no framing at all, no sequencing of requests and no ability to match a response with a request other than hoping the response you got is for the last request you sent. Most of the time this is okay, but as soon as the device doesn’t respond or takes too long to respond things get weird. You also have an issue where if any other system connects to this thing you’re potentially sending uncontrolled/mixed data over the serial line.

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