| Computer Networks and Linux have been developing so fast that they have settled a base for applications which are based on Embedded Linux, and they will promote the applications too. Embedded Linux will certainly change the reality pervasively, and take us into a characteristic Pervasive Era. Specially, this new mode will surely revolute the architecture of control systems so that they can be more open and perform better.With existing techniques and good prospect, we try to develop a new kind of control system architecture in which the embedded-Linux -controllers work as net node and they communicate equally by Switched Ethernet;In this way,there have not been hierarchies within the control networks compared with the traditional principal-and-subordinate ones. Acordingly, sophisticated control systems which need fast and much communication can be built in the architechture above. Although Ethernet has been applied most widely for its well-known priorities,the common Ethernet is not suitable for field communication in industry because of indeterminacy of CSMA/CD.In order to sovle this basic problem,we use Switched Ethernet. The key techinics of Switched Ethernet control networks when used in industrial field include:1, Making sure to be within real time.2, Free from Circle and Broadcasting.3, Supporting the security of network.4, Power supply of Bus.5, Mutual operation.6, Network surviving.7, Nature security and anti-explosion.8, Remote transmission.Now that the communication devices have been set up, the other important aspect is developing embedded-Linux controller. There is something in common although the practical developments differ very much. The Data Monitoring System in Slim Steel Section based upon embedded-Linux has been developed in such a way that reflects how to develop an embedded-Linux controller. The system is offered as an instance as well as outcome, and it is practical. So, we show the developing procedure as following.Firstly, systematical analysis. After analyzing , it is determined that an embedded-data-monitoring system, instead ofthe traditional communication card that links the IPC and Monitoring Center, can be put into practice to directly join together with the Switched Ethernet control network, so that the user can monitor the industrial field using Internet/Intranet conveniently.Secondly, hardware architecture designing. Adopt SOM5307A and WH5307DB directly since they meet the need.Thirdly, software architecture designing. The system use the preloaded OS uCLinux-Coldfire as its embedded OS, use Boa as embedded Web server whose CGI programs communicate with the Dataserver through writing message queues and reading message queues. The Dataserver is designed in such a way that its main process circles infinitely while reading the messages from the serial port driver and from Web server in turn. And the history data from serial port is stored in the memory of the Dataserver in the form of Circle Queue.Forthly, build up a developing environment. Firstly, the developing host be installed .Secondly, the source code of Wanhe Embedded Linux and the compiling tool software be installed. Thirdly,the target system be installed. Forthly,operate and control the target system.Fifthly,set up the IP address of the target system. Finally, run the image after being compiled and transferred to the target system .Fifthly, code and debug.Lastly, simulate and test.In order to make the essay more representative, it is described how to develop the data system above into a Data Gateway that links Intranet and FieldBus(eg. LonWorks), and this Gateway can be looked on as a special controller based on Embedded Linux.In the end .another questions are discussed, including the attention that should be given to hardware designation. |
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