Hello,
I have got two PLCs and I need to establish the communication between them via a Modbus. Due to security reasons PLC A must be accessible only via Modbus RTU and simultaneously it must be a Modbus RTU master. The distance between both PLCs is around 50 meters and unfortunately there is no cable. So my idea is to use RUT956 which would be connected to PLC A via RS485. On the other side I am going to use RUT200 which would be connected to slave PLC B via ethernet cable, using Modbus TCP. The RUT200 would be then connected to RUT956 via wifi (RUT956 as AP and RUT200 as client). Would this kind of topology be possible? However, if not, would be then possible to replace rut200 by another rut956 so that the communication would be via Modbus RTU on both sides?
Thanks for any hints
Hello,
An important consideration is that Teltonika Networks devices can forward and convert Modbus TCP requests to Modbus RTU (and return responses), but they do not support converting Modbus RTU to Modbus TCP when a Modbus Client is connected via RS232/RS485.
This TCP to RTU feature is called “Modbus TCP over Serial Gateway” , but I’m not sure if it fully meets your requirements. You can find more details here:
Modbus TCP over Serial Gateway.
Alternatively, you could use two Teltonika devices with RS232/RS485 interfaces (such as RUT956) and connect them using the Serial over IP feature. This setup will enable serial devices on both ends to communicate by simply forwarding raw serial data/requests over TCP.
For a bidirectional communication example between two serial devices over TCP/IP, refer to this guide:
Bidirectional Communication Between Two Serial Devices Over TCP/IP.
Lastly - yes, you can connect both devices using WiFi. However, be mindful of the distance between them, as WiFi range can vary significantly depending on the environment. You can find general estimates of the WiFi range for Teltonika devices here:
Kind Regards,