Design and Development of Modbus/MQTT Gateway for Industrial IoT Cloud Applications Using Raspberry Pi

The Industrial Internet of Things (IIoT) concentrates on the interconnection and utilization of big and powerful data in manufacturing environments. Data from different devices and different protocols needs to be converted for making these devices IIoT-ready. Today a large number of serial Modbus-based devices still exist in industrial applications. MODBUS RTU is the most widely used industrial protocol for connecting industrial devices and almost all major industrial instrumentation and automation equipment vendors continue to support it in new products. Modbus protocol follows a master- slave model. MQTT is a messaging protocol suitable for the Internet of things (IoT). The MQTT protocol is based on the principles of publishing messages and subscribing to topics commonly known as the publish / subscribe model. In this paper, we have designed a Modbus to MQTT gateway for Industrial IoT cloud applications using inexpensive Raspberry Pi single-board computer and a RS485 add-on board with the necessary integrated circuits for data communication. It supports two-way communication between field devices and cloud applications, and supplies a Modbus RTU interface on RS485 to communicate with on-site field devices. It contains smart-agent at the gateway side to process and convert data sent from the field level of different data formats into the IoT-standard MQTT protocol and pass periodically the unified data to the public or private cloud service applications (Amazon AWS, Alibaba Cloud, or MQTT Broker etc.) for future analyses. Based on embedded web server, the configuration of the gateway is performed through web pages, and updates can be performed over the air when necessary. The proposal gateways provide an easy and secure way to build the IIoT applications now and in the future. Moreover, it can be added to a system and take advantage of the IIoT world while the existing operational technology stays in place.