【正文】 如果網(wǎng)絡中某個設(shè)備出現(xiàn)故障，車載網(wǎng)關(guān)能夠自動監(jiān)測到，發(fā)出指令將該設(shè)備復位并重新入網(wǎng) 。該車載網(wǎng)絡系統(tǒng)能夠自動完成網(wǎng)絡的配置。 結(jié)語 本文分析 E 802． 15． 4 和 ZigBee 協(xié)議，結(jié)合通信系統(tǒng)和嵌入式系統(tǒng)的一般開發(fā)原則，在 μC ／ OSII 操作系統(tǒng)上實現(xiàn) IEEE802． 15． 4 協(xié)議，選擇合適的軟硬件平臺，著重于軟件支撐平臺的構(gòu)建、軟件總體結(jié)構(gòu)設(shè)計以及通信協(xié)議棧的實現(xiàn)，最終實現(xiàn)了一個符合 ZigBee 規(guī)范的車載星型無線數(shù)據(jù)采集網(wǎng)絡。星形網(wǎng)射頻通信誤碼率測試結(jié)果如表 1 所列。最后統(tǒng) 計數(shù)據(jù)結(jié)果，就可以知道數(shù)據(jù)的丟包率和誤包率。 4． 2 ZigBee 射頻通信測試 測試設(shè)備： ZigBee 節(jié)點 4 個，計算機終端 1 臺。 測試方法：網(wǎng)關(guān)節(jié)點上電后， 4 個 LED 同時點亮，掃描信道如果搜索到空閑信道后， LED 熄滅并加入空閑信道等待。在車載系統(tǒng)運行過程中可能關(guān)心某一個車載傳感器節(jié)點的數(shù)值，或者需要對某一個傳感器進行閾值設(shè)置，以便待監(jiān)測的環(huán)境出現(xiàn)異常情況可以及時地報 告給系統(tǒng)。 ③ 歷史數(shù)據(jù)顯示模塊。這個應用程序包括了 4 個模塊： ① 實時數(shù)據(jù)顯示波形模塊。 3． 4 主機監(jiān)控軟件的設(shè)計 本系統(tǒng)最終目的是將采集到的車載傳感器數(shù)據(jù)實時地傳送到主機，并在主 機 中得到顯示和保存。 圖 4 傳感器節(jié)點主程序流程 3． 3 網(wǎng)關(guān)節(jié)點軟件設(shè)計 車載網(wǎng)關(guān)向下管理傳感器節(jié)點，向上完成和 PC 監(jiān)控中心的交互，需要進行復雜的任務管理和調(diào)度，因此，采用基于 uC／ OS 內(nèi)核的嵌入式操作系統(tǒng)管理整個網(wǎng)關(guān)，為應用任務的高效運行提供良好的軟件平臺支撐。 通過測試發(fā)現(xiàn)， ZigBee 模塊的能耗要遠遠大于中央處理器和傳感模塊的能耗。協(xié)議層則實現(xiàn)了基于 IEEE 802． 15． 4 的物理層和鏈路層以及基于 ZigBee 的網(wǎng)絡層協(xié)議。系統(tǒng)層接口定義了硬件的寄存器映射，這樣 C 語言就能直接訪問硬件寄存器來控制硬件。因為 SMAC協(xié)議棧編程模型采用層次設(shè)計，只有底層的 PHY 和 MAC 程序?qū)优c硬件相關(guān)，而網(wǎng)絡層和應用層程序則不受硬件影響。同時， MCU 完成 MC13192 收發(fā)控制和所需要的 MAC 層操作。MCU 通過 SPI 口進行 MC13192 的讀寫操作，并把傳感器采集的信號經(jīng)過處理后通過 MC13192 發(fā)射出去。 2． 2 MCl3192 與 MC9S08GB60 的硬件連接 MC13192 與 MC9S08GB60 的硬件連接圖如圖 2 所示。這種功能豐富的雙向 2． 4 GHz 收發(fā)器帶有一個數(shù)據(jù)調(diào)制解調(diào)器，可以在 ZigBee 技術(shù)應用中使用。為了提高通信傳輸模塊的智能化水 平，在設(shè)計中，它的功能不限于數(shù)據(jù)的實時顯示，所有的數(shù)據(jù)采集由監(jiān)控軟件通過發(fā)送請求信號的方式觸發(fā)。 圖 1 系統(tǒng)結(jié)構(gòu)總體圖 車載傳感器節(jié)點的生命周期由活躍期和休眠期構(gòu)成。車載監(jiān)控中心可以向車載網(wǎng)關(guān)發(fā)出控制命令，由車載網(wǎng)關(guān)將控制命令轉(zhuǎn)換為射頻信號后發(fā)送給車載傳感器節(jié)點。該采集系統(tǒng)的應用對象由溫度傳感器、油壓傳感器、轉(zhuǎn)速傳感器、速度傳感器、電流 傳感器、壓力傳感器等傳感器子系統(tǒng)所組成。目前，汽車電子設(shè)備廣泛采用 16 位或 32 位微處理器進行控制。 monitoring system Introduction In order to satisfy the people to car safety, handling and fort requirements, vehicle integrated with more and more electronic system .At present, car electronic equipment is widely used 16 or 32bit microprocessor control. Creating invehicle monitoring system based on IEEE and ZigBee standard for wireless sensor works, designed to achieve a more optimized wireless sensor works, the progressive realization of the work of automotive systems, intelligent and controllable to provide highCar System security. System design In this paper, the existing vehicle system, the data transmission mode is extended to the wireless transmission mode, the realization of a star work 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 puter, in the host data realtime waveform display, and method of database to preserve, for the followup data processing. The application of system object is posed 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 plexity, using timedivision multiplexing way, one by one on the 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 munication. Vehicle monitoring center to the gateway sends a control mand by the gateway, the control mand 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 municate with each other. The monitoring center of the monitoring software and gateway in RS232standard interface for munication. Vehicle sensor node life cycle is active and dormant periods. Nodes in the active phase of the pletion of data acquisition, data sent to the gateway, receiving and executing gateway mand。 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 softw