Study And Design On Remote Temperature Measurement System Based On UClinux And Web

With the rapid development of technologies of digit communication and network, the society of science and technology has entered the era of post-PC. Most of computers of this age will exist in the form of embeded system. For thirty years since embeded systems came forth, embeded operation systems have been indispensable for embeded systems. Through embeded operation system, embeded system can manage hardware devices of bottom system, call all the application tasks to function, afford the application interfaces to hide details of bottom hardware, which makes developers work in application layer so that the process of application design is enormously simplified and the efficiency is improved for the development of the applications. The technology of embeded operation systems has been developed while a large number of different embeded operation systems came out, such as Microsoft Windows CE, PSOS, VxWorks, PalmOS and so on. Among them, Linux makes the whole IT industry gain new energy and becomes one of important symbols in the post-PC age since it possesess many merits, such as open source, system stability, kernel reducability and abundant applications. Though Linux itself needs enough hardware in order to adopt virtual memory management technology, considering sensitive factors (e.g. cost etc.), usually processors without memory management unit (MMU) are adopted in embeded devices, for example microprocessor S3C4510 used in my project. uClinux is designed to non-MMU processers and inherits a majority of merits of mainstream Linux. uClinux follows Linux development way. Its applications are mostly developped in the native approache, namely host development, host debug and host function. But this method is not usually available to develop applications of embeded system, for host or the board system, has not enough resource for the development of embeded system to use tools to compile and debug. The method of cross-compiling is generally adopted to develop applications of embeded system. Cross-compiling environment is set up in host or PC and its corresponding evaluation board is called target board. For the project, compiler and debuger afforded by GNU are development tools used as open source tools. The project is mostly involved in remote temperature measurement system based on uClinux and Web that can test and measure temperature value from remote local workplace by using Web technology as communication method in uClinux development environment. The system of my project adopts Browser/Server mode in its structure which is separated into three layers. The bottom layer is data collection system collecting data from remote temperature sensors and executing control instruction. The second layer is signal process system. In this system the server receives local data and their related information which is measured and analyzed, then distributed and sent dynamicly to client part in the form of Web page. The third layer is client that receives information sent by network, directly using and testing data from local workplace by browser. The design of project is involved in key techniques as followed. 1. Embeded HTTP server is established in the mode of Client/Server, intercepting port 80 by daemon and then offering service. The brower is corresponding to the client of embeded HTTP server. Embeded HTTP server is set up in the environment of UNIX alike, which needs programming network socket. Socket sets up communication connection among processes in Client/Server. Embeded HTTP server of the project is made up of server daemon module, process selection module and message header process module. Based on URI process selection module selects CGI dynamic process or static net page and Java Applet process to further deal with requests. 2. Common Gateway Interface (CGI) is a sofeware module inside HTTP server and can execute programs stored in it. CGI script and HTTP server are responsible to respond client's request. HTTP server calls CGI corresponding to the requests, returns result to the client and closes communication. Traditionally HTML document is static. The applications are executed with the requests by CGI script and dynamic results are produced so that there is interaction between browser and embeded Web server becauce users can gain real-time data and control devices by browser. 3. Java applet is specially executed in browser. While Web browser with JVM downloads a HTTP document embeded with Applet, sign must be added in Web page. After the brower meets the sign, it will download the corresponding applet class and startup its interpreter to execute applet. It makes Web interfaces agile and friendly to use Java Applet in Web page. Java Applet in the system is maked up of two parts, graghical interface and network connection.