An IoT Gateway for Modbus and MQTT Integration

The IoT technology has brought many new features to the automation solutions in general. Despite the news, there are also some concerns with the legacy automation processes, since industry has lots of data-gathering devices, most of them created and installed a long time before IoT concept emerge. The technology to bring legacy equipment to IoT solutions, indeed, is not totally new, since it involves the use of gateways. IoT gateways bridge devices to the Internet in the context of real-world applications. This paper presents a low cost IoT gateway prototype to bridge conventional Modbus RTU sensors/actuators to a MQTT IoT cloud. The methodology used consists in implementing bidirectional functional mappings between Modbus RTU and a MQTT broker. Two sets of events were defined in this mapping: one for Modbus alerts and other one for MQTT commands. The gateway prototype was validated in a scenario in which IoT Sensors generate events to update a monitor panel controlled by a CLP connected to the prototype. The results were promising since the integration allowed a transparent and efficient operation for the gateway in several different scenarios in the laboratory.