Question

We have been succesfully using RUT955 as RS485 Modbus gateway in several scenarios.

Our Modbus TCP master sends requests to router openVPN IP and most of them get answer.

We notice that the number of failures increases significantly as the number of RTU device increases.

Now “Modbus serial master” feature has come available, but we do not find (if there is any) the way to allow Modbus TCP requests to be routed to serial (Modbus TCP slave seems to be limited to RUT955 id and registers).

The aim is to let the RUT955 bufferize the requests and that seems to be possible since I have read that values are stored in ram.

We kindly ask advice.

Answer 1

Hello,

Modbus Serial master and Modbus gateway are two different functions.

Modbus serial master is a function, which allows user to configure periodical data collection from connected serial devices and send to server via HTTP(S) or MQTT. External Modbus TCP master commands cannot be routed to this function.

If you want to send Modbus TCP request to Modbus RTU devices, then you have to use RS485 Modbus gateway mode, which is located in Services -> RS232/RS485 -> RS485

Only Modbus serial master buffers collected data in RAM, since it does not need external requests to read data from connected slave devices.

I hope that I have answered your question. If not, please let me know what I have missed.