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  Embedded System Smart Transducer Networking  

Sensor networking is a key issue for monitoring and control applications. The embedding of increasing amounts of intelligence in transducer (sensor/actuator) nodes and the diversity of the transducer market have resulted in a profusion of low cost solutions for smart transducer networking. This has resulted in various fieldbus/control network solutions targeted towards specific applications such as the Controller Area Network (CAN) for the automotive industry, LonTalk® for factory automation in industrial control networks, BACNet® for office and building automation, etc.

Recent industry efforts towards interoperability in a wide range of applications have attempted to focus on the definition, functionality, and communication protocol standards for smart transducers. The Institute of Electrical and Electronics Engineers (IEEE) and the National Institute of Standards and Technology (NIST) have defined the IEEE 1451 set of standards for a Smart Transducer Interface for Sensors and Actuators in an effort to overcome the incompatibility issues that arise while interfacing smart transducers to instruments, microprocessor-based systems, fieldbus and control networks. The objective of these standards is to define an architecture that allows transducers to connect into any live distributed control network in a true plug-and-play fashion, such that automatic system identification and configuration is facilitated.

The use of wireless communications for networking smart transducers is an attractive option and promotes an adhoc, portable, wireless connectivity model. Recent research efforts in wireless sensor networks have focused on designing low power, energy-efficient protocols for communication between sensor nodes, where typically thousands of sensor nodes participate in the communication.

For small-span transducer networks, the use of an existing wireless technology may prove to be a quicker, cheaper and more optimal solution. The main requirements of such a transducer network would be prolonged low-power operation, ability to form self-organizing networks, and the use of a “light” communication protocol that may be easily embedded in the smart transducer nodes. An example application for a small span wireless smart transducer network is within an Unmanned Aerial Vehicle (UAV) that is remotely monitored by a high speed RF link. The UAV may possess one or more Bluetooth “piconets” for monitoring environmental condition (ex. Temperature/Pressure), engine condition (ex. Motor speed/Emission), aircraft condition (Tank/Instruments), and the actual application of the UAV (law enforcement/pollution control).

An analysis of the existing short-range wireless communication technologies, viz., IrDA, HomeRF, IEEE 802.11x, and Bluetooth suggests Bluetooth as the best alternative for wireless smart transducer networking on account of its low power operation, easy embeddability into smart transducer nodes, and its capability of proximity networking. The main argument against the use of Bluetooth technology is the unavailability of Bluetooth products at the originally projected low costs but the technology is expected to become popular rapidly the same way that IEEE 802.11x has established itself in the wireless market.

The interfacing of the IEEE 1451 Smart Transducer nodes to a Bluetooth network involves a detailed study of the network communication models specified for smart transducer communication as well as the Bluetooth protocol stack. For embedded systems, it is advantageous to include more complexity in hardware, with semiconductor and VLSI technology paving a way for System-on-a-Chip (Soc) implementations. The objective of this project is to understand the issues for developing the interface (network infrastructure) between IEEE 1451 Smart Transducer nodes and Bluetooth communication in hardware, and provide a proof-of-concept VHDL implementation of the network infrastructure.

Deepika Devarajan