Wireless sensor network monitoring system designKang yi-mei,Zhao lei,Hu jiang,Yang en-bo(Study on Beijing University of Aeronautics and Astronautics)Summary: A car wireless sensor network monitoring system based on IEEE 802.15.4 and ZigBee standards. With universal wireless sensor networks, expansion of the scope of monitoring and monitoring functions for in-car system, car data acquisition and condition monitoring of equipment status and the necessary equipment control, topology control, topology query functions. Keywords: wireless sensor networks; monitoring systemIntroductionIn order to satisfy the people to car safety, handling and comfort requirements, vehicle integrated with more and more electronic system .At present, car electronic equipment is widely used 16 or 32-bit microprocessor control. Creating in-vehicle monitoring system based on IEEE 802.15.4 and ZigBee standard for wireless sensor networks, designed to achieve a more optimized wireless sensor networks, the progressive realization of the network of automotive systems, intelligent and controllable to provide high-Car System security.System designIn this paper, the existing vehicle system, the data transmission mode is extended to the wireless transmission mode, the realization of a star network data acquisition system. And can place each data acquisition node of the acquired data is transmitted to the gateway, the gateway through the serial port to upload data to the host computer, in the host data real-time waveform display, and method of database to preserve, for the follow-up data processing. The application of system object is composed of a temperature sensor, pressure sensor, speed sensor, speed sensor, a current sensor, pressure sensor, sensor subsystem. The purpose of this design is to use a monitoring host machine end to the detection of multiple target environment, taking into account the access data throughput and software system complexity, using time-division multiplexing way, one by one on the net terminal collecting point of control and data acquisition.As shown in Figure 1, the system is divided into 3 parts: Vehicle Monitoring Center, gateway and mobile sensor node. Gateway is the whole vehicle system core, and all vehicular sensor node communication. Vehicle monitoring center to the gateway sends a control command by the gateway, the control command is converted to an RF signal and sent to the vehicle sensor node. When the vehicle sensor nodes to transmit data, gateway into the data reception state, and upload data to the monitoring center for further processing. In addition, car between sensor nodes cannot communicate with each other. The monitoring center of the monitoring software and gateway in RS232standard interface for communication.Vehicle sensor node life cycle is active and dormant periods. Nodes in the active phase of the completion of data acquisition, data sent to the gateway, receiving andexecuting gateway command; in the dormant period off the wireless RF module in order to save energy, until the next active period. System through this mechanism of dormancy to reduce energy consumption, extend the time span of the system as a whole.The system used PC as the control center, PC machine monitoring software in VB development environment, is a dialog based application software. In order to improve the communication module of the intelligent level, in the design, its function is not limited to the real-time data display, all of the data collection by the monitoring software by sending a request signal to the trigger. Considering the original data for subsequent processing and in-depth analysis of the vehicle system, can accurately judge, software has also added data preservation of the document and data file display function.Generally speaking, the whole network are controlled by the host monitoring software, the working process of every node of the network is the need of human participation.2 hardware system design2.1application chip introductionMC13192with IEEE802.15.4 standard, the operating frequency is2.405～2.480 GHz, data transmission rate of 250kbps, using 0-QPSK debugging mode. This feature-rich two-way 2.4GHz transceiver with a data modem which can be in the ZigBee technology application. It also has an optimized digital core, helps to reduce the MCU processing power, shorten the cycle of execution.The main control MCU choose HCS08series of low power, high performance microprocessor MC9S08GB60. The processor has a 60Application of KB programmable Flash、4 KB RAM,10 ADC,8 channel2 asynchronous serial communication interface ( SCI ),1 synchronous serial interface ( SPI ) and I2C bus module, can fully meet the requirement of vehicle gateway and node processor requirements.2.2 MCl3192and MC9S08GB60hardware connectionMC13192and MC9S08GB60 hardware connection diagram as shown in figure 2. The MC13192control and data transmission on 4 wire serial peripheral interface ( SPI ) is completed, the4interface signals were MOS-I, MISO,, SPICLK. The main control MCU through the control signal exiting sleep mode or hibernation mode, through to reset the transceiver, through the RXTXEN to control the data sending and receiving, or force the transceiver into idle mode. The sensor output analog signal through MCU 8 Channel10 bit ADC conversion input to MCU. MCU via SPI MC13192to read and write operation, and the sensor to collect the signal processed by MC13192launch out. The MC13192 interrupt IRQ interrupt register through the pins and to judge the type of interrupt. MC908GB60 pin to control the MC13192 into a different mode of operation .Control of the sensor signal from the MC13192receiving antenna in, transmitted via SPI to MCU, after MCU judgment after processingthrough the GPIO port is transmitted to the sensor, complete control of the sensor. At the same time, MCU MC13192transceiver control and the MAC layer operation. The 3system software design3.1of overall software designThe software design is the design of the core, the key lies in the overall framework of software and data structure design. An important factor to consider is a efficiency, another is to design the clarity.System software consists of the gateway node and the sensor node is composed of two parts, the two parts are needed to complete the SMAC protocol transplantation, and according to the different needs for the upper communication applications with API interface function. Because the SMAC protocol stack programming model using hierarchical design, only the underlying PHY and MAC program level and related hardware, and network layer and application layer procedures is not affected by hardware effects. SMAC in different hardware platform transplantation only need to modify the PHY and MAC layer, each layer can shield the hardware differences directly run.As shown in Figure 3, the design of the software for system platform layer, protocol layer and application layer 3layer. At the same time, defines 3API interface: system layer interface, protocol layer and application layer interface. System level interface defines a hardware register mapping, so C language to be able to directly access the hardware registers to control hardware. System platform based on real-time operating system μC/II protocol layer, to provide system services Hardware driving module provides the hardware driver, all of the hardware control through the module to provide services. Platform layer protocol layer interface protocol layer to provide services. Protocol layer is based on the IEEE 802.15.4 physical layer and link layer based on the ZigBee network layer protocol. Application layer through the application layer interface to invoke services provided by the protocol layer, network management and data transfer tasks. Application of configuration module can call protocol layer to provide network services, will direct the system configuration and query, it is mainly through the AT commands to achieve, so the module calls the application layer interface and protocol layer interface to provide services.3.2sensor node software designBased on the long-term use of the functional requirements, sensor nodes in the software design is the key to achieve the required functions, and can minimize the energy consumption of the sensor nodes.It was found, ZigBee module and the energy consumption is much larger than the central processor and the energy consumption of sensor module. Therefore, the sensor node design of application software to try to make each module in a dormant state, and minimizing wakes ZigBee module number. Therefore, the sensor nodes, power of each functional module initialization is completed, and joined the network, enter the Sleep state, the central processor cycles to be timed wake-up to send data tothe gateway, and receives the gateway command. Sensor nodes of the workflow are shown in Figure 4.The 3.3 gateway node software designGateway downward management sensor node, to complete and PC monitoring center of interaction, the need for a complicated task management and scheduling, therefore, based on the uC / OS kernel of embedded operating system to manage the gateway, the application task efficiently provide good software support. According to gateway function demand, the μC / OS-II, SMAC protocol organic union, form a network operating environment, the user can conveniently on the basis of its development and application. Based on μC / OS-II extended gateway software platform structure is shown in figure 5. Based on μC / OS-II operating system, were used to build the system task SYS_task ( ), START_task ( SMAC star network task ), gateway and a sensor node interaction task COMM_task ( ), PC monitoring center port monitoring mission ( SER_task ) applications such as a series of tasks, thus realizing the gateway software application function.The 3.4 host monitoring software designThis system is the ultimate goal of the collected vehicle sensor data is transmitted in real-time to the host, and the host of display and preservation. Display is designed to get on-board sensor node monitoring environment of the initial situation, preservation is designed as an in-depth analysis of the data samples. In addition, the system as a whole the main prosecution and the data acquisition request initiator, need to be able to send the data request signal in accordance with the requirements of. According to the above requirements, VB environment in the development of a dialog based application. This application includes a 4 module:①data waveform display module. The role of the module is a form of waveform data of the node to be displayed in real-time, it is the use of MS Chart and Timer control.②topology display module. When the user wants to know the wireless sensor network topology construction situation, you can view the topological information, understanding of network nodes join and loss.The historical data display module. In vehicle network system to a certain period of the past, may need a certain period of time the original data for subsequent processing and in-depth analysis, so that the vehicle system of accurate judgement. With the aid of historical data display module, the control center from the gateway of the data obtained, according to the different attributes of the nodes, address and time are saved to the database of the corresponding field, and may be will displayed by waveform of historical data, for the user analysis.The controlling module :In vehicle during system operation may be concerned about a vehicle sensor value node, or to a sensor threshold settings, for monitoring environmental exceptions can be promptly reported to the system. These are available through the control module of the system are corresponding to the set, the control module can also be on the system in which one does not need to delete the node.In short, through the host monitoring software users can visually and many aspects ofgeneral wireless sensor network systems to understand and use.4 test and verification4.1 testingTesting equipment:4 MCl3192ZigBee chip node,1as a gateway node, the remaining 3as sensor nodes.Test method: the gateway node power,4 LED and light, scanning channel if the search to the idle channel, the LED goes out and join the free channel for. The sensor node power,4 LED scanning in the channel at the same time, polling light. LED1 flashes once when the sensor nodes receive the allocation address of the gateway node, So far, networking process and address binding process is complete.4.2 Zigbee RF communication testTesting equipment: ZigBee node 4, a computer terminal stationTest method: according to the ZigBee transmission frame format, the actual transmission total bytes for ( n 6), namely ( n 6) bytes for a data packet. According to the set parameters of the software, such as packet loss is the loss number plus 1. If the received data packet, receives the data packet number plus 1, and then sends the data were compared with data, if the data is correct, the number of packets plus 1, and error packets number plus 1. The last statistic results, can know the data packet loss and packet error rate. The 4 node to form a ZigBee network,1 of them as the gateway, the remaining 3 nodes for sensor node. Write a program to set:3nodes and gateway communications, computer terminal and the gateway is connected through RS232, terminal equipment software records from the 3node to receive data, nodes work at 2.4 GHz frequencies, transmission of a byte of data, circular send 100 times. To obtain the final3 node test average as a result of the data analysis. Star network radio frequency communication BER test results as shown in table 1.Experimental analysis of: in a star network for data transmission, the test results significantly worse on a single point to single point transmission mode. This is mainly because, in the transmission process node must exist between the frequency interference and other interference.4.3power testSystem status and hibernation, respectively, using a multimeter to test the gateway node and the power consumption of sensor nodes, the test results listed in Table 2.ConclusionThis paper analyzes the IEEE 802.15.4 and ZigBee protocol, combined with the general development principles of communication systems and embedded systems, IEEE802.15.4 protocol on the μC / OS-II operating system, select the appropriate hardware and software platform, focusing on software support for the platform, the software design of the overall structure of the communication protocol stack, andultimately to achieve a compliant with the ZigBee specification car star wireless data acquisition network. The system has the following advantages:①system easy to install. Wireless interconnection makes the equipment installation location is flexible to meet the requirements of the automation system is installed. It is simply that the power can take equipment. The network system can automatically complete the network configuration.②scalability. Equipment within the coverage of the vehicle gateway, turn on the device, the node will automatically join the network.③network self-healing ability. If the network is a device fails, the vehicle gateway can automatically monitor, issue the command the device reset and re-network.车载无线传感器网络监测系统设计康一梅，赵磊，胡江，杨恩博（就读于北京航天航空大学）摘要：基于IEEE 802．15．4和ZigBee标准实现了一个车载无线传感器网络监测系统。