Development of a HART compatible HART line powered communication module

The HART protocol is a specification designed for industrial process automation and control. In this paper we provide the design and implementation of the communication module with HART protocol. The primary objective of the designed hardware is to minimize current consumption so that the module is powered by a 4-20 mA current loop. The employed parts have also been selected with regard to the minimum current consumption. Another requirement for the proposed module was its galvanic isolation from the measuring device. Communication between the HART communication module and the measuring device is implemented as shared access to the I2C EEPROM and FRAM. The basic idea for the software development was to use real-time operating system and divide the program into separate processes with mutual communication. As an operating system we choose FreeRTOS, which is able to perform processes (tasks) on the basis of events as well as to use preemptive scheduling. By a suitable proposal of hardware and software we managed to present a flexible solution that meets the former requirements.