1 Introduction
Contactless IC card, also known as radio frequency IC card and RFIC card, is a new type of smart card that emerges from the combination of radio frequency identification technology and IC card technology. Since its appearance, it has become an important development direction of these two technologies. Due to the advantages of security, larger storage capacity, better adaptability to the application environment, simple reading and writing equipment, and fast operation speed, its technology and application have developed rapidly, and it has been widely popularized in China. It is believed that with the development of large-scale integrated circuits and manufacturing technology and the maturity of development tools, non-contact IC cards are bound to be widely used in various fields in China.
2 System working principle
The MFRC530 sends radio frequency signals of a certain frequency through the transmitting antenna. When the radio frequency card enters the working area of ​​the transmitting antenna, an induced current is generated. The radio frequency card obtains energy and is activated; the radio frequency card sends its own code and other information through the card's built-in transmitting antenna; The carrier signal sent from the radio frequency card is transmitted to the MFRC530 through the antenna regulator. The MFRC530 demodulates and decodes the received signal and sends it to the microprocessor for related processing; the main system judges the legality of the card according to logical operations. Make corresponding processing and control for different settings, and send out different prompt sounds through the buzzer. The schematic diagram is shown in Figure 1.
Figure 1 System functional block diagram
3 System hardware circuit
3.1 Introduction of MFRC530 chip
MFRC530 is a member of the 13.56 MHz contactless highly integrated IC card reader module. The module utilizes advanced modulation and demodulation concepts and fully integrates all types of passive contactless communication methods and protocols at 13.56 MHz. MFRC530 supports all layers of Isol4443A communication.
The internal transmitter part can directly drive the antenna (up to 10cm) for short-range operation without adding an active circuit.
The receiver part provides an identical and effective demodulation and decoding circuit for ISO14443A compatible transponder signals.
The digital part handles ISO14443A frames and error detection (parity and CRC). In addition, it also supports fast MIFARE typical security algorithms for verifying MIFARE series products.
The convenient parallel interface can be directly connected to any 8-bit microprocessor, which provides great flexibility in the design of the card reader terminal. In addition, it also has features such as support for SPI interface.
3.2 MFRC530 circuit connection
MFRC530 is the core module that realizes wireless communication with the radio frequency card, and is also the key interface chip for the card reader to read the radio frequency card. It modulates the data in the transmit buffer according to the settings of the register to obtain the transmitted signal, which is sent out in the form of electromagnetic waves through the antenna driven by the TX1 and TX2 pins. The RF card responds with load modulation of electromagnetic fields. The response signal picked up by the antenna to the RF card is sent to the RX pin through the antenna matching circuit. The MFRC530 internal receive buffer detects and demodulates the signal and processes it according to the register settings. The processed data is sent to the parallel interface and read by the microprocessor. The circuit connection is shown in Figure 2.
Figure 2 MFRC530 circuit connection
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