Design And Implementation Of Wireless Sensor Network Node

Wireless Sensor Network (WSN) is a new altitudinal crossed multidisciplinary intelligent control and monitoring network combining sensor technology with computer and communication technology,has become a hot spot in the field of wireless communication. It is data-oriented and self-organizing compared with traditional control and monitoring networks. It has been widely used in Military, Environmental Monitoring Systems, Traffic Management Systems, Disaster Prevention System, Dangerous Region Monitoring Systems, Security Monitoring Systems of Civil and Engineering Establishment, Biomedicine Monitoring Diagnosis or Treatment Systems, Environmental Systems, Smart Home Systems and so on.Now, the research hotspot of WSN is focus on the Sensor communication protocol (MAC and route protocol), energy conservation question, node localization, time synchronism, data collection and management, network service security and so on. This dissertation is foused on the building of the wireless sensor node hardware and the realization of the node communication protocol,which is low frequency band on the ZigBee's protocol theory.Controller of node of WSN mostly uses the 8bits or 16 bits single-chip on the purpose of low cost. But now the price and power consumption of 32 bits microprocessor is falling year by year with the development of Semiconductor Technology and micro-electronics integration technology, this kind of microprocessor can install system, Its computation speed is faster, The storage capacity is bigger. And the price of ARM 9 processor falls to about 10$ now. So I choose the ARM 9 core piece which composed with the S3C2410, 64M RAM and 16M nor Flash. In this way, we can install embed Linux system, make sure that the software can steady run, we can easily design and update the programs and the WSN nodes can be reused. In this system, the Linux is configured with the ppcboot bootloader, 2.4.18 kernel and ramdisk file system.In this system, I choose the data Temperature sensor DS18B20 and the simulation gas sensor MQ-4, both of which are the single line. In order to drive the DS18B20 and the MQ-4, I designed two drivers as the rule of character equipment drivers. The single line equipment DS18B20's driver is designed as a modulation, and I select one ordinary I/O pin of the S3C2410 F port (can choose anyone available port) as the single line connection. In the Linux system, I treat the DS18B20 as an external instrumentation to open, read and write. The MQ-4 gas sensor is a simulation single line equipment, because the S3C2410 chip itself has the AD transformation function, so if I write to the suitable register I can read the corresponding simulation size. In the Linux system, to protect system, the user can not directly operate on the hardware port and the register, so we must read or write them through the kernel's system calls or the drivers. The MQ-4 gas sensor's driver also is designed as the ordinary character device driver. The DS18B20 and The MQ-4 can load into the kernel with dynamic or static way. When I debug the programmers, I can load the driver through the USB device. After I finish the debugging, then I can load the programmers into the kernel with static way.Currently, we mostly use the ZigBee technology to research about the wireless sensor network protocol and to organize the network and to transmit the data wirelessly, The WSN has not a standard protocol stack. The ZigBee technology is low power loss,low cost,and low complexity, these characteristics are very suitable to the wireless sensor network, Therefore, the presently, the most applications are based on the ready-made ZigBee development suite which provides by Freescale or Microchip Corporation, and also there are minority applications which have own hardware platform, but the software was still based on the ZigBee stack developed by Freescale or Microchip Corporation provides. Howover, the transmitting range of ZigBee technology generally is about 100 m. This system has researched the theory of ZigBee technology, and made the suitable revision about the frequency band,the structure of transmission data frame and network protocol to make sure the data can be transmitted farther. This dissertation detailedly introduces the wireless communication protocol which is designed based on the ZigBee theory by myself:The physical layer protocol is mainly to open,close,read,write and make some judgment,classify to the wireless radio module load in the serial port; The MAC layer realizes the CSMA-CA based on the non-time slot; The network layer uses the Cluster-Tree routing algorithm to realize the Tree Topology; The application layer realize the network initialization,the data memory and the multi-thread programming mechanism to realized parallel running multi-module in Linux.