Sub-1GHz Wireless RF Network Control System with Modbus TCP Gateway

Posted on August 9, 2026

Watch the Application in Action:

In this industrial automation setup, we demonstrate an end-to-end 868MHz (Sub-1GHz) RF wireless control network powered by the RDF-GW2 Linux Gateway. Managing 10 remote I/O nodes without physical control cabling, this application provides reliable remote motor control and seamless SCADA integration via Modbus TCP.

System Architecture

The wireless network is engineered to handle real-time field control across long distances through a distributed master-remote setup:

RDF-GW2 (Linux Gateway PC): Functions as the master controller for the 868MHz RF star network. Runs programmable Lua scripts within the RDF-GW2 subsystem to manage long-range node polling and event-driven communication.
Modbus TCP Slave Interface: Built directly into the RDF-GW2 to expose field I/O data to the client's central SCADA system over standard Ethernet.
RDF-CPU (Remote RF Controller): Installed at each of the 10 remote field locations operating at 868MHz, serving as the central processor for local I/O modules.
RDF-88DM Extension Module: Snapped to the right side of the RDF-CPU to supply 8 Digital Inputs and 8 Digital Outputs per node.
Auxiliary Contactor Feedback: Connects to single-option auxiliary contacts on the remote AC motor contactors, enabling real-time verification of physical switching states (ON/OFF).

Key Features & Operating Logic

Intelligent Star Polling & Intercept

While the RDF-GW2 continuously queries all 10 remote nodes sequentially, immediate commands or status changes automatically interrupt the main loop to execute zero-delay commands.

Programmable Lua Engine

Custom Lua scripts executing on the RDF-GW2 subsystem allow fully customized timing, automatic retry logic, and custom packet processing over sub-GHz wireless links.

SCADA & PLC Integration

By converting 868MHz RF telemetry into Modbus TCP registers, higher-level SCADA systems monitor and actuate remote motors with zero added hardware converters.

Modular I/O Expansion

The RDF-CPU architecture allows field engineers to seamlessly attach digital and analog expansion modules to suit evolving application requirements.

By eliminating expensive cable trenching and long-distance wiring runs, this solution delivers a reliable, low-latency wireless control network suitable for severe industrial environments.