Enhancing the Modbus Communication Protocol to Minimize Acquisition Times Based on an STM32-Embedded Device

Abstract

The primary function of a distributed bus is to connect sensors, actuators, and control units that are used for an acquisition process. Application domains, such as industrial monitoring and control systems, manufacturing processes, or building automation, present different requirements that are not exactly invariable and coherent. Updating data from Modbus-type devices involves updating data through a technique called polling, which involves repeatedly scanning the registers from each device. This paper highlights the performance of Modbus communication, considering scenarios in which distributed devices are integrated and accessed registers are or are not at consecutive addresses. The Modbus protocol allows reading one or more holding-type data registers. If the registers are not at consecutive addresses, multiple requests are required, with implications for the real-time characteristics of the data acquisition system. We studied the data update times within the SMARTConvert application when variable numbers of registers are accessed, and we designed an extension for the Modbus protocol. The major reason Modbus is used in current research is that no assumptions are required about application semantics, and the performance/resource ratio for generic services is excellent.

Keywords

• Modbus
• remote terminal unit (RTU)
• acquisition cycle
• industrial Internet of Things
• communication