Rhydo SIM 900 SIM 900 -TTL UART Manual do Utilizador descarregar pdf (Página 2)

GPRS Based ARM Embedded Web Server Design

DOI: 10.9790/2834-10221015 www.iosrjournals.org 11 | Page

Fig 1 shows proposed DAC system with embedded web sever. This contains a portable ARM processor.

This hardware built on a single chip module. An ARM processor is responsible for handling all tasks like

measuring & conversion of signals, data base updating, communicating with owner by sending HTML pages. An

ARM processor manages all tasks in parallel in small amounts of time. The use of GPRS is familiar to all. Almost

all GSM system providers give this service. So it is easy to be connecting to the internet world.

Fig 1. Embedded web server architecture

After a GPRS connection has been established queried data can be relayed to the client via a central

server [7]. Real-time system correctness depends not only on the correctness of the logical result of the

computation but also on the result delivery time [8]. This method also increases the data transfer cost as the

number of clients increases due to the access amount of data transfers via GPRS. Direct communication enables

access to only relevant information in the embedded system by pre processing the data. The embedded system

should also handle the web services. Using a central server to relay acquire data has some disadvantages. It needs

a client interface framework. There is no direct bidirectional communication between client & embedded system.

This system is unsuitable for real time applications. So it is necessary to eliminate the need of a central server &

reduce the amount of data sent from the remote unit. In the proposed system, the GPRS architecture works with

GSM protocols [9]. Because of GSM network, this system is configured to be virtually online at all times. After

booting of the operating system an admin script is executed, initiating GPRS connection software module. It

supports instructions of AT commands. SIM 900 can be integrated with many applications. GSM/GPRS RS232

Modem from rhydoLABZ is built with SIMCOM Make SIM900 Quad-band GSM/GPRS engine, works on

frequencies 850 MHz, 900 MHz, 1800 MHz and 1900 MHz. It is very compact in size and easy to use as plug in

GSM Modem. The Modem is designed with RS232 Level converter circuitry, which allows you to directly

interface PC Serial port .The baud rate can be configurable from 9600-115200 through AT command. Initially

Modem is in Auto baud mode. This GSM/GPRS RS232 Modem is having internal TCP/IP stack to enable you to

connect with internet via GPRS. It is suitable for SMS as well as DATA transfer application in M2M interface.

The IP address of embedded devices should available at client side to directly access an embedded system. By

using IP address people from remote location can access the information.

There are two types of IP address i.e static IP & dynamic IP. Dynamic IP assigned through a Dynamic

Host Configuration Protocol (DHCP) server of the GSM provider for every connection established. The DHCP

approach is more flexible and works better compared with the static approach as a cost-effective solution, despite

the necessity for a script running on the embedded server, one-time broadcasting its IP to the FTP server. The

hypertext file placed on the FTP server by the embedded system and queried by the client. With this mechanism

in place, the embedded system updates it IP information on the FTP server upon every reboot, which causes an IP

refresh from the GSM service- provider.

III. System design

3.1 Data Acquisition System

The remote I/O data acquisition and control system based on embedded ARM platform has high

universality, each acquisition and control device equipped with 24-way acquisition/control channels and isolated

from each other. Different types of sensors such as temperature sensor, Humidity sensor, speed sensor, carbon

monoxide detector, and LPG gas leakage sensor are connected to each I/O channels of ARM processor. The data

from sensors is collected & maintain by the ARM processor. The data is stored into the database. Due to their

tiny size and low power consumption, LPC2148 are ideal for applications where miniaturization is a key

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