A brief analysis of access control systems based on RFID technology

　　Automation, informatization, and intelligence have become demands of the times. Since entering the 21st century, infinite technology and computer technology have continued to deepen, and the IoT industry is thriving. Access control systems based on RFID technology are a good example of the practicality of the Internet of Things. Access control systems can be divided into three main categories based on entry and exit identification methods: password recognition; Card recognition; Biometrics. Password recognition verifies entry and exit permissions by verifying whether the password entered is correct. Password recognition is relatively more secure, but passwords are easy to forget and require entering each entry, which is cumbersome. Biometrics refers to identifying certain human characteristics. Biometrics is highly secure and very convenient, but its high cost makes it difficult to adopt. Card recognition is divided into two categories: the first uses magnetic cards, but magnetic cards are less secure, wear out easily, and require frequent magnetization; The second type is RFID cards, which are cheap, easy to use, highly secure, and can be well managed through databases. They offer excellent cost-performance and great prospects for promotion.

　　In summary, this article introduces an access control system based on RFID technology, which is low-cost and highly secure. It is possible to view information about access control systems in real time.

　　1 Overall Structure and Working Principle

　　The overall system architecture consists of two parts: the upper computer server management system and the lower computer card reader. The lower computer card reader mainly consists of six parts: power supply, main controller, LCD display, card reader/write module, antenna, and serial communication. Among them, the reader/write card module M102GPCV3 uses 13.56MHz contactless RF technology, capable of reading MifareOne S50, S70, FM11RF08, and compatible cards. The LCD displays some prompt information and the date and time. The serial port is used for communication between the lower computer and the host computer server. The host computer server management system uses MySQL database management, with the specific management interface displayed via a web page.

　　The working principle of the entire access control system is: one person, one card, and based on the serial number of the card, corresponding personal information is created in the database management system. When opening the door, the card is swiped on the lower computer. The lower computer's card reader sends the serial number to the host computer's server, which then queries the corresponding personal information in the database based on the serial number and sends it to the lower computer. At the same time, the lower computer reads data from the fixed sector of the card (card reading), compares the read data one-to-one with the data sent by the host computer, and only opens the door if it matches exactly the same data; otherwise, an error will be displayed on the LCD and the door will not open. All of the above information will be uploaded to the host computer management system for storage. The upper computer management system can change the data information set by the lower computer (card writing).

　　2. System hardware design

　　2.1 Overall hardware design

　　The main controller of the access control system is the ARM-STM32F103VET6 chip with the Codex-M3 core, clocked at 72MHz, with 512KB on-chip flash, and contains multiple USART controllers for RFID read/write module connections and communication with the host computer. The read/write module uses a M102GPCV3 module with a working frequency of 13.56MHz. The main control board uses the JTAG port for program debugging and downloading, while the LM117 provides 3.3V and 5V voltages to the system board. I/O port connected to the 12864 LCD is used to display relevant prompts and dates. USART1 is connected to the card reader module to read card information, while USART2 is connected to MAX232 for communication with the host computer.

　　2.2 Hardware design of the card reader module and main controller circuit

　　M102GPCV3 read/write module design offers two interface modes: 10Mb/s I2C bus mode and up to 1228.8Kb/s UART mode. Here, a UART mode is used, allowing card information to be read and written through M102GPCV3.

　　3. System software design

　　3.1 Overall System Software Design

　　The overall software design of the access control system includes the software design for the lower computer card reader and the upper computer database management system software design. The card reader for the access control system's lower computer mainly enables card reading and communication with the upper computer management system, programmed in C in the Keil4 environment. The host computer management system is written using Myecfipse and Firefox programming tools. As shown in Figure 3.

　　3.2 Software design of the lower computer card reader system

　　The lower computer access control card reader system is shown in Figure 4. The lower computer card reader system must follow ISO14443TYPEA standard transmission protocol, i.e., following the sequence of card search→ anti-collision → card selection→ key authentication→ and block reading. During conflict prevention, the serial number is read and transmitted to the host computer management system, where it is saved in the database management system. Block reading data is read and compared with preset data for judgment.

　　3.3 Software design for the upper-level computer database management system

　　The host computer database management system records and publishes information when cardholders swipe to enter the premises, as well as add, delete, and modify cardholder information and permissions. Information is stored in a database, and information tables are made in Java language and published on the website. Ordinary users can log in to their regular accounts to visit LAN websites and check information about access control systems. Administrators can log in to modify card information and permissions through their administrator account.

　　4 Conclusion

　　After multiple physical tests, the RFID access control system designed with this solution is safe, reliable, and easy to use. Moreover, compared to other access control systems, it offers a very high cost-performance ratio. With the rapid global development of IoT technology and the promotion of China's Gold Card project, it is believed that RFID technology will be increasingly applied across various industries. RFID-based forbidden systems will also develop alongside this trend. The facts prove this: statistics show that in 2008, RFID access control sales accounted for 87.2% of the entire security market.