华中科技大学
硕士学位论文
远程数据采集系统的设计与实现
姓名：吴雪峰
申请学位级别：硕士
专业：计算机系统结构
指导教师：谢长生
20070604
摘要
在进行数据采集时，由于许多被测对象距离较远或现场危险，只能在远距离的地方进行测量，然后传输出去，这便产生了远程数据采集系统。远程数据采集系统有着自身的特点：首先，为了精确和全方位获取环境信息，系统一般要提供多个采集通道进行高速采样；其次，为方便用户随时了解系统的运行状况，系统在高速采样的同时，必须能以异步接收和处理控制站的命令、传输用户所需数据；另外，远程数据采集系统一般仅靠电池供电，于是低功耗成为衡量系统性能的重要指标。
从实时性、远程可控性、低功耗的目标出发，提出由FPGA（现场可编程门陈列）作为数据采集控制部分、由嵌入式微处理器系统和单片机作为数据存储和传输部分的数据采集系统。外部信号通过前置放大、滤波后，在FPGA的控制下进行高速数模转换和缓存；采集到的数据由嵌入式微处理器系统进行读取、处理和存储；数据通过RJ-45网络接口或无线数传模块传输至远程上位机。
单片机在系统中有三个作用：一是提供用户操作输入接口及系统状态指示灯等信息；二是当嵌入式微处理器系统在高速采集和存储时，可以异步的接收来自控制站的无线命令，并对命令进行分析和处理；三是对嵌入式微处理器系统进行电源控制，在不需要采样时可以将嵌入式板的电源断开。
与通常的仅仅采用单片机或嵌入式微处理器系统的采集系统相比，同时采用两者可以将用户接口和采集任务分开，使采集系统在保证吞吐率和实时性的同时能处理用户输入或来自控制站的无线传输命令。另外，单片机对嵌入式微处理器系统的电源控制功能可以达到降低系统功耗的目的。
关键字：数据采集，嵌入式系统，无线数据传输
Abstract
Since many objects being observed are out of our territories or they are in dangerous places, it is wise to sample data of them in where they are, and then send the data back to where we are, called long-distance data acquisition system, which has some unique characteristics as follows. First, in order to know the objects or environment of the sampling place more exactly, more sample channels are required. Secon d, these devices must be able to receive orders and send back information that the supervisor needs. Third, the power supply of these systems are usually batteries, thus low power consumption becomes an important devising guideline of these systems.
Aiming to get the quality of real time, long-distance controllability, and low power consumption, a data acquisition system is proposed which compose of the following elements, a FPGA-based sampling board, an embedded CPU, a single chip and a wireless data transferring module. Exterior signals are first amplified, filtered, and then transformed from analog signals to digital signals under the control of FPGA board. The digital data is then buffer by the FPGA board. Digital data is then fetched by embedded CPU system, which handles and stores it in hard disks at the form of files. These files then are sent to the personal computer, which can analyze them, either by internet or by a wireless data transferring module, depending on the real conditions.
The single chip has three functions in the system. First, it provides the input/output interface to the operator; second, it can exchange data asynchronously with long-distance control center; third, it controls the power switch of the embedded CPU system, that is, it can shutdown the embedded CPU system when it is no need to collect data.
Compared with data acquisition systems which only use single chips or embedded CPU systems, combining these two can separate user interfaces from sampling and storage task, thus can make the system take in and send out in large quantities, while it can communicating with the control center. Besides that, the power controlling function of the single chip can reduce the consumption of power of the whole system.
Keywords: Data Acquisition, Embedded System, Wireless Data Transfer
