Access control, also known as an access control system, is a digital management solution that allows authorized individuals to enter and exit secured areas. With the rapid development of industrial automation and the increasing demand for advanced security solutions, access control systems have become widely adopted. However, traditional systems often separate access control from video recording functions, which leads to complex wiring and higher costs. The embedded access control system described in this paper, built on ARM9 and Linux, integrates both access control and video recording capabilities, offering a more efficient and cost-effective solution. It details the software design of the system, utilizing a B/S (Browser/Server) architecture, the embedded server BoaServer, CGI technology, an embedded database, and a graphics library to meet all functional requirements.
The access control monitoring system operates using a B/S architecture, where the access controller is equipped with an Ethernet interface and built-in TCP/IP protocol and web server functionality. Once connected to the network, users can manage the system directly through a browser without needing any additional software. This approach simplifies user interaction and enhances usability.
The system comprises several key components, including an ARM9-based access controller, a card reader, an electric lock, and a front-end camera. When a person attempts to enter or exit, the card reader detects the card and sends the information to the access controller. The controller then verifies the card's legitimacy by checking it against a user database. If the card is valid and has the necessary permissions, the door is unlocked. At the same time, the camera captures the image during the door opening process and transmits it to a storage device for later review.
Clients can remotely access the system via a browser, enabling them to manage user information, authorize access, configure hardware, monitor video feeds, and view data. This makes the system highly flexible and easy to manage from any location.
In terms of hardware, the system uses ATMEL’s AT91RM9200 microcontroller, based on the ARM920T core, running at 180MHz with a performance of 200 MI/S. The operating system is Linux version 2.6.25, with 64MB of NOR Flash and 32MB of SDRAM. The system also includes an LCD controller for debugging purposes and supports up to 256 card readers and cameras.
The software architecture is divided into two parts: the foreground and the background. The background runs a monitoring program that continuously checks for card swiping activity, while the foreground handles client requests using the Boa server and CGI scripts. The system function model is illustrated in Figure 3.
The front-end consists of the Boa server and CGI service programs. The Boa server monitors incoming requests and triggers the appropriate CGI script to handle them. CGI, or Common Gateway Interface, is a standard method for web servers to execute programs and return results to the browser. It works by processing input from HTML forms or links, executing the required application, and returning the output as a web page.
Boa Server is a lightweight, single-threaded embedded server that supports CGI. Its small size (around 60KB) and fast performance make it ideal for this project. It needs to be cross-compiled for the ARM platform, and its configuration file must be adjusted to set up directories for logs, static web pages, and CGI scripts.
On the backend, the system runs a main monitoring program in either debug or monitoring mode. In debug mode, users can configure the IP address, set admin credentials, and manage card permissions using the MiniGUI graphical environment. MiniGUI is a lightweight GUI framework for embedded Linux, providing a message-based interface similar to Windows.
In monitoring mode, the system continuously checks for card information. When a valid card is detected, the background program verifies it against the database. If the check passes, the door is opened. During this process, the camera captures the image and stores it in the database. To prevent conflicts, the front-end CGI service communicates with the background via named pipes to obtain and release database access rights.
Given the frequent database operations, the system uses Berkeley DB, a reliable and high-performance embedded database suitable for Linux environments. This ensures smooth and secure data handling throughout the system.
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