Networked Low-Power Sensing: Network Interface and Main Operating System

Abstract

The Defence Science and Technology Organisation has developed a low-power RS485 networked sensor interface for condition monitoring of structures, monitoring environments, or any other monitoring tasks. The core of the sensor interface consists of sensor invariant software and hardware and is based on the low-power Texas Instruments MSP430 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> series of micro-controllers. For any particular sensor(s), the interface consists of the core module which is linked to specific hardware and software for the sensor(s). Advantages of this approach are faster hardware and software development times and a consistent interface to any data logging or network control system. The core software manages communications, data logging, low-power modes, sensor addressing, the on-chip programmable memory (including the capability to modify the sensor interface software in the field), and a number of user accessible library routines (including full floating point calculations). An optional Secure Digital Card <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> (SDC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> ) can be implemented allowing large amounts of data to be stored locally. The unit is 40 mm wide, 16 mm high, and typically 55-65 mm long, depending on the complexity of the sensors interface. This paper will present the design and characteristics of the core sensor interface with one example for a simple sensor interface.