INTRODUCTION
The usage of web server systems for information interchange has been quite a common practice. Analyzing the condition of an environment by knowing the physical parameters is a general requirement now a day. This project is meant for introducing a advanced web server system for controlling the physical environment in an embedded manner.
After the “everybody-in-the-Internet-wave” now obviously follows the “everything in the Internet-wave”. The most coffee, vending and washing machines are still not available about the worldwide net. However the embedded Internet integration for remote maintenance and diagnostic as well as the so-called M2M communication is growing with a considerable speed rate. Just the remote maintenance and diagnostic of components and systems by Web browsers via the Internet, or a local Intranet has a very high weight for many development projects. In numerous development departments people work on completely Web based configurations and services for embedded systems. The remaining days of the classic user interface made by a small LC-display with front panel and a few function keys are over. Through future evolutions in the field of the mobile Internet, Blue tooth-based PANs and the rapidly growing Machine-to-Machine communication a further innovating advance is to be expected.
The central function unit to get access on an embedded system via Web browser is the Web server. Such Web servers bring the desired HTML and pictures over the worldwide Internet or a local network to the Web browser. This happens HTTP-based. A TCP/IP protocol stack –that means it is based on sophisticated and established standards– manages the entire communication. Web server and browser build TCP/IP applications. HTTP achieved a phenomenal distribution in the last years. Meanwhile millions of user around the world surf HTTP-based in the World Wide Web. Today almost every personal computer offers the necessary assistance for this protocol. This status is valid more and more for embedded systems also. The HTTP spreads up with a fast rate too.
Block Diagram:
Embedded Web Server for a Process Control
An embedded system is basically a computer system that forms part of a larger system, which is typically non- computing in nature, for e.g. TV, VCR, automobile or an industrial robot. Unlike a general-purpose computer system, which can run much different application software, the software of an embedded system is specifically designed for the larger system of which it forms a part and is rarely changed. This is usually referred to as Firmware
The main purpose of process control system with temperature sensors is to maintain the temperature of 4 heaters. The readings are maintained in an embedded web server, which is configured as a node in the LAN with a unique IP address. Any node in the LAN can access the server. There is a TCP/IP stack in the system and a dynamically created web page will be sent to any client connected to the server. The client can request the page with a web browser. The technology used in Embedded Web Server is Cross Platform Development.
Cross Platform Development
When a software code is written, compiled, and executed on the same machine it is said that the compiler produces native code. This is called a self-hosted system. However, there are compilers, which will run on one system (host), but generate code for another system (target). This code can be subsequently linked and downloaded into the target machine and executed there. This is called cross-development. Cross-development is convenient, when the host system offers an easier development environment, but more often it is a necessary because the target may not have the user interfaces required to support development activities.
ADMINISTRATIVE INTERFACE
The embedded web server is be controlled by the administrator. A password is set up for the administrator to prevent the on slotting of data. The administrator is capable of accessing the source page and making the sufficient changes in the control of the physical quantities. The main aim of the system is to notify the parameter and change its value according to the requirements. This part of the system specifies the control section. For example in temperature sensing scenery in a manufacturing company, there exists a necessity of maintaining the value on correct locations and positions at various stages like preparation of raw materials, burning and processing stages etc. the cut off value of the temperature can be decided and setup by the administrator at right occasions.
In short the Admin interfaces the PCS through a serial port. The administrator can change the temperature settings of the heater through this interface after authentication. Authentication is met using a password requirement accessible at the administrator PC only.
USER INTERFACE
The parameter measured at a location should be made available at distances. If a Local Area Network is used, then the results available in the administrating computing machine will be available in the whole network. Instead it can be even connected to the Internet so that the processed valued can be evaluated and studied by various authorities at different distances. The measured pressure or temperature values that are expressed in tabular and graphical forms can be visualized by in the website corresponding to the PCS embedded Web Server system.
The user interfaces the PCS through a Web Browser. The user can view the temperature readings of the heater through a graph created dynamically by the web server.
SYSTEM INTERFACE
A process control system is present that consists of sensors. At a time four different measurements can be done and the values can be interpreted using this advanced server. For example in a temperature solely measuring case, four temperature sensors can be used. To maintain the temperature, 4 heaters are to be switched on/off. The temp readings are to be taken every 1 second. Each channel is having different set points and if the reading falls below the set point the heater is to be switched on for that channel. A dynamic web page is created using the readings and sent to the client /user in the html format. Instead of four temperature sensors a pressure transducer can also be used along with other sensors. The readings of the different sensors are analyzed and the required process control point can be installed to various sensors.
TCP/IP
· Connection to Single PC via cross-over Ethernet cable.
· Connection to LAN or WAN via Ethernet cable.
Connection to Modem or GPRS phone via RS232 and PPP or SLIP interface
Architecture of Embedded TCP/IP
IP works by exchanging pieces of information called packets. A packet is a sequence of bytes and consists of a header followed by a body. The header describes the packet's destination and, optionally, the routers to use for forwarding until it arrives at its final destination. The body contains the data which IP is transmitting.
Due to network congestion, traffic load balancing, or other unpredictable network behavior, IP packets can be lost or delivered out of order. TCP detects these problems, requests retransmission of lost packets, rearranges out-of-order packets, and even helps minimize network congestion to reduce the occurrence of the other problems. Once the TCP receiver has finally reassembled a perfect copy of the data originally transmitted, it passes that datagram to the application program. Thus, TCP abstracts the application's communication from the underlying networking details.
SOFTWARE SECTION
The Firmware Implementation
The Firmware is developed in Embedded C.
The Firmware Modules
1. Implementation of the TCP/IP Stack, on the micro controller by programming the on-chip Ethernet controller and the external transceiver DP83848.
2. Creation of a dynamic web page to be transmitted by the system through the Ethernet port. The page will be refreshed at regular interval with the new ADC values.
3. Initialization and processing of the Timer Interrupt to time the packet transmission.
4. Configuration of the ADC to start conversion and reading the converted temperature values.
5. Implementation of the LCD interface (16 x 2) to display the system status.
6. Programming the micro controller ports as output controls to regulate the heaters.
7. Programming the UART as an interrupt with authentication for the admin interface to set up different parameters of the system
Software Tools
The software tools used are:
KEIL ARM Real view cross compiler
Optimizing C Compiler to compile
C programs for the target ARM board.
KEIL µVision3 IDE
Integrated development environment to create the source files and organize them into a project for the target application. The compiler runs on the host machine
COMPONENTS LIST
MICROCONTROLLER
ARM LPC2368
SENSORS
Temperature sensor
Pressure sensors
PERIPHERALS
ADC
Ethernet transceiver
Ethernet controller
APPLICATIONS OF EMBEDDED WEB SERVER
1. The MCB2300 prototype board offers a 10Base-T (RJ45) Ethernet connection. This standard interface can be used for fast data transmissions in a local area network (LAN) to PC’s or other micro controllers.
2. In case the LAN is connected to the Internet via a router, data can be exchanged worldwide.
3. The software to handle the Ethernet interface is much more complex than for a serial interface.
4. In most cases, the TCP/IP protocol is used for data transmission because it provides a fast and reliable connection to other members of the LAN.
5. The simple web server uses the TCP/IP stack. It can only handle one web page but it can insert dynamic values.
6. The web page that is created by this server shows the input voltage of analog input 0 and 1 as a bar graph on the screen.
7. The values of the A/D converter are inserted into the web page instead of special strings.
The above conference Report is not complete, few image are there which i haven't upload.
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