TCP/IP Implementation Using Embedded Controller
Contents
1. lt html gt lt head gt lt title gt Temperature Monitor lt title gt lt head gt lt body gt lt hl gt Temperature Monitoring Demo lt l gt lt p gt Temperature lt echo var Temperature gt lt p gt lt body gt lt html gt A Server Side Include directive uses the same delimiters as a HTML comment A comment which is text that the browser ignores and doesn t display is enclosed by lt and gt On receiving a page that contains an HTML comment the browser displays the page the same as if the comment and its delimiters weren t present Another use for comment delimiters is to enable a page to specify Server Side Include SSI directives that the server executes before serving the page to the browser Before serving a page containing an SSI directive the server executes the directive and replaces the delimiters and the text between them with the result of executing the directive If for some reason the server doesn t support the directive the server ignores the directive and the browser treats the directive as a comment which isn t displayed Till this point it has been stated about web page design In the following section the development of embedded application is described The application requires the dcrtcp lib library which supports TCP IP and related protocols and the Attp lib library which supports HTTP To make embedded web server application these libraries has to be2. Fig 3 Resistor Divider Network for Analog Inputs The above diagram shows the input circuitry of the AD7870 The resistive divider acts as a 10 1 attenuator and the capacitors are used to filter out noises The core module has RTL8019AS Ethernet controller and RJ45 connector The RTL8019AS is a highly integrated Ethernet Controller which offers a simple solution to implement a Plug and Play NE2000 compatible adapter with full duplex and power down features With the three level power down control features the RTL8019AS is made to be an ideal choice of the network device The full duplex function enables simultaneously transmission and reception on the twisted pair link to a full duplex Ethernet switching hub Ths feature not only increases the channel bandwidth from 10 to 20 Mbps but also avoids the performance degrading problem due to the channel contention characteristics of the Ethernet CSMA CD protocol TEST AND RESULTS In this work an embedded application is developed to serve the web page with dynamic content and with the user interfaces like buttons The embedded application is tested in a Local Area Network After downloading the web page and the application by removing the programming cable the processor is put into run mode In run mode when the Controller is reset it starts execution from 0 x 000000 The board is connected to the hub via a straight through cable It is assigned an IP address of 192 168 1 4 and a sub
3. It must be called periodically for the daemon to work In this work the remote control is also done by using some user interfaces such as buttons in the web page By clicking the button the remote user can give commands to microcontroller which in turn controls the relay HARDWARE DESIGN The MCS51Controller is used to host web pages This microcontroller has 5 parallel ports six serial ports three timer units Timer A Timer B and Timer C This microcontroller has 24 bit address bus and it needs two clock inputs One is fast clock used as processor clock and a slower clock for peripherals like Real Time Clock Watchdog Timer etc This Controller reduces the EMI though it runs at the maximum clock speed of 125 MHz The internal blocks Clock doubler and spectrum spreader are used to reduce EMI In this work Ethernet core module is used with its prototype board This core module has Ethernet Controller 512K Flash 512K SRAM an A D converter AD7870 and optional NAND Flash 32 kHz 44 2 MHz SRAM Flash Customer s pecific applications ss g CMOS level signals converter NAND Flash RS 232 RS 485 serial communication A D Converter drivers on motherboard Module Fig 2 Ethernet module Sub Systems TCP IP Implementation Using Embedded Controller In this core module A D converter AD7870 s 8 Channel LN7 is connected to thermister such that the temperature variation is sensed as voltage variation
4. included The MCS51 module has 8 channels 12 bit Analog to digital converter AD7870 This ADC supports programmable gain and it has a conversion time of 180us In this application a thermistor is used to measure the temperature and the temperature is stored as a variable which will be attached with the web page and served to client sock_init http_init tcp_reserveport 80 while 1 update_temp http_handler Mobile and Pervasive Computing CoMPC 2008 In above code segment sock_init initialize the packet driver and transfer control protocol http_init initialize the http daemon This must be called after sock_init and before calling http_handler in a loop This sets the root directory to and sets the default file name to index html Tcp_reserveportis used by servers to give special treatment to remote sockets that connect to the specified port If a connection is made to a reserved port and there is currently not a listening socket to handle it the system will try to hold the connection open until a listening socket is available This allows a server to handle multiple requests smoothly even if only a few sockets are allocated Port number 80 is reserved for Hyper Text Transfer Protocol Then in an infinite loop two functions are alternatively called in which update_temp is used to update temperature values and the library function http_handler is a tick function to run the http daemon
5. TCP IP Implementation Using Embedded Controller S Ganesh Sri Muthukumaran Institute of Technology Chennai 69 ABSTRACT This paper deals with the design of an Embedded Web Server based on MCS51Family Controller The designed embedded system hosts a small w eb page which is served with the dynamic data upon the client http request The entire system is developed around MCS 51 and Ethernet development board This system enables a user to monitor and control a physical quantity from a remote location through Internet Keywords TCP IP Embedded Ethernet Simple Mail Transfer Protocol SMTP INTRODUCTION AS Embedded system is device that has computer intelligence and dedicated software to perform a single task or group of related tasks Embedded Systems are often used to do monitoring and controlling functions such as gathering sensor readings and controlling relays and motors Ethernet is the technology used to connect computers in home and offices It is also possible to interconnect networks by router and Gateways The work done in this paper bridges the gap between the Ethernet technology and Embedded Systems One development that has made Ethernet feasible for embedded systems is the availability of inexpensive controller chips to handle the details amp Ethernet communications The CPUs that provide the processing power for embedded systems have also faster and more capable of handling the demands of communicating with the con
6. ecifies the for matting of text and images on the page including text size and fonts and the positioning of text and other elements on the page The HTML code may include links to images that appear on the page as well as links to other pages or resources In serving a Web page with dynamic content the software must have a way of inserting the dynamic content as the page is being served SOFTWARE DESIGN The heart of the Embedded Web server is the software which is running in it In this work using Dynamic C Integrated Development Environment develops the software To make the Controller communicate to Internet TCP IP stack should be implemented in the software The software development in Dynamic C is easier as it comes with TCP IP stack Many Web pages are static That is the content of web page remains the same for every http request It doesn t have any dynamic content like date or time the value of which is changing Embedded Web servers are often used to display the real time information such as sensor reading 90 from a remote location This necessitates that the web page is served with dynamic content Here the dynamic content is the sensor reading which may change with time To deliver the web page with dynamic content Server Side Include SSI directives are used It instructs the server to insert the values of variable in the appropriate locations in the web page The following HTML code includes SSI Directives
7. he distributor through internet to tell that it is going out of stock Like this Internet communication capabilities of the Embedded Systems will start new avenues in Embedded Automation Industry This project can be enhanced using CAN controller for processing CAN data and using Wireless sensors to gather parameters Having been in the starting of 21 Century We our self witnesses the rate of spread of internet through out the globe So by giving Internet Communication capabilities to your embedded system you are providing the capability to your system to communicate with every corner of this planet 92 REFERENCES 1 Hashmi Atif G Mdik Haroon W Pervaiz Aman and Younas Muhammad Efficient and Cost Effective Approach to Control and Monitoring Area Network CMAN IEEE Tr Internet comp 2002 2 Axelson Jan Embedded Ethernet and Internet Complete Designing and programming small devices for networking Penram Publications Mobile and Pervasive Computing CoMPC 2008 3 http www Siliconlabs com 4 MCS5100 user manual 5 Wu Li Wei and Hu Jwu Sheng Distributed Embedded Ethernet Platform for Robots Control IEEE International Conference on Mechatronics Taiwan 2005 6 Richard Stevens W TCP IP Illustrated The Protocols Volumel
8. net Mask 255 255 255 0 Then the processor is reset to run the application Now in a desktop PC which is connected to the same network a browser application is opened In the address bar of browser the IP address 192 168 1 4 is typed to make an http request to the Embedded Server After getting the http request from the client the server delivers the web page with the dynamic content 91 The following figure shows the web page delivered by the Embedded Web Server File Edit view qe Gack E3 B fat E Search G Favorites http 192 168 1 4 bd Favorites Tools Help Address l Ee i i Eer A Fig 4 Snapshot of web page served by Embedded Web Server To connect the Ethernet kit to internet the board has to be connected to an Internet modem with a static IP address and the web hosting service is allowed by the Internet Service Provider CONCLUSION amp FUTURE WORK In this paper design of an embedded web server based on MCS51 Microcontroller is presented The application developed in MCS51 works as a web server The application is capable of serving the web page with dynamic content The user in the client machine can also give command to the microcontroller by the User Interfaces in the Web page There are plenty of applications in which it is so useful that an Embedded System should communicate to the world through internet For example a vending machine which sells the cool drinks can communicate to t
9. trollers Internet protocols provide standard well documented ways of exchanging data Both Ethernet and the Internet protocols are free and open standards available for use without royalties or licensing fees EMBEDDED WEB SERVER Normally Web Server is a computer in which lot of web pages are stored Web Server for hosting a corparate web page should have the capability to handle more traffic The aim of this work is to neither hosting a corporate web pages nor handling much traffic Internet a ETHERNET ie MODULE Temperature Sensor Analog signal Fig 1 Block diagram representation of Embedded Web Server CLIENT An embedded system that functions as a Web server generally has all of the following e Non volatile memory to hold pages to be served e Support for TCP and IP Requests for Web pages and the pages sent in response travel in the data portion of TCP segments e Support for HTTP The server must be able to understand and respond to receive requests for Web pages The HTTP standard specifies the format for the requests and replies e A local network or Internet connection To serve pages on the Internet the Web server must have an Internet connection Any firewalls must be configured so the system can receive HTTP requests e One or more pages to serve The Web pages are files or blocks of text that use a form of encoding called hypertext markup language HTML The HTML encoding sp
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