The Design Of The Wireless Sensor Network Universal Node

The Wireless Sensor Network(WSN) is composed of sensor nodes, and sink node, and management node. Many sensor nodes are distributing in monitoring area, which constitutes a network that is self-organizing. The sensor nodes typically relay their sensed data through each other or to the sink node with a Multi-Hop and self-organizing way. The collected data of the sink node is transmitted to the management node by Internet, Satellite and Mobile Communication Network. The user marshals the WSN and manages it, issues the monitoring commands and collects the monitoring data by the management node. Possessing the characteristics of small size, low power, good removable ability and different acclimatization, the sensor node will be applied in many fields.A wireless sensor network universal node was designed in this paper in order to design sensor nodes that can be used for different demands. The universal node is hardware-based on the low-power MSP430F149 and CC2420, its reliability and practicability has been tested. This project is divide into tow parts, the first part is hardware design, and the second part is relevant software design and is debugging.1. Hardware DesignThe universal node includes RF transceiver module, Microprocessor module, Power Management module, universal interface module, and PC interface module.The RF transceiver module is used for realizing communication between sensor nodes and base stations in wireless sensor network. The Micro- processor module is used for controlling communications between sensor nodes and realizing Calculations. The Power Management module is used for applying power for every module of the universal node and checking the health status of power. The universal interface module is used for applying right interfaces for special sensor nodes. The PC interface module is used for realizing communications between PC and universal nodes.The low-power CC2420 which meets the standard of 2.4GHz IEEE802.15.4 is used as core of wireless transciever module. The chip provides hardware support for data packet processing, data cache, pulse series transmission, data encryption, data authentication, remove channel assessment, link quality monitoring, and time information of the data packet. The ultra-low power MSP430F149 is used as the processor, which realizes data collection and computing between the universal nodes, and controls communications between them. The microprocessor collects status of CC2420 and controls the RF transceiver of CC2420 by SPI. FT232BM of FTDI company is used for realizing signal conversion between USB of PC and RS232. A virtual COM coming into being on the computer is used to realize the download and upload data by MSP430UBSL based on the USB.The PCB thickness must be designed following the thickness of the RF section, because the RF section works in High Frequency of 2.4GHz and its thickness is ordered to 1 millimeter. The universal node is designed into tow modules, including separating module and integrating module. It has tow debugging methods, BSL and JTAG. The BSL is used for downloading C program from USB of PC, and the JTAG is used for downloading C program from the parallel interface of PC.The distance test experimentation of the universal node indicates that it is better than the previously buying node in transmission and penetrability.The design of universal node takes fully account of the expansibility and flexibility of node, adopts the method of module design, and defines the unified and fully functional external interface of the WSN universal node, which is used for designing different special sensor nodes.2. Software DesignThe software design of the universal node is the C program design between MSP430F149 and CC2420.Firstly, the SPI communication between MSP430F149 and CC2420 should be designed, through collocating the registers of MSP430F149 to realize the SPI program of CC2420, and then controlling the RF working of CC2420. Secondly, according to the CC2420 datasheet, subprograms about relevant read and write commands, register configuration, read register, read and write RAM of CC2420 is designed. Furthermore, relevant initialization program of CC2420, transmit and receive subprogram and the main function are designed to the universal nodes.CC2420 has hardware support for parts of the IEEE802.15.4 frame format. The frame control field describes frame formats as beacon frames, data frames, and acknowledgment frames, while the data frames are used for programming the C program of the universal nodes. Of the MAC protocol data unit there are frame control field, data sequence number, destination address, source address, data payload, and frame check sequence which is automatically generated and verified by hardware. 3. ConclusionIn this paper, according to the transmission and low-power characteristics of sensor node and limitations of the buying node, the universal node that has the maximum flexibility and adaptability was designed. The node'characteristics about stability, security and reliability have reached the corresponding requirements. It is also designed to the special sensor node such as gas meter, water meter, ammeter and so on.The design of the universal node is described by five chapters in this paper. The first chapter is an introduction, which simply introduces the conception, characteristic, application, and design of sensor node of the wireless sensor network, and describes the significance of the GM node design. The second chapter describes the whole design scheme of software and hardware of the node. The third chapter describes the hardware design of the node. The fourth chapter describes the software design of the universal node and its C program flow chart. The last chapter gives the figure of real node and the testing data and its conclusion.