RFID (electronic tags, radio frequency identification) technology will penetrate into all aspects of our lives in the future. Its working principle is that "the low frequency band is based on the transformer coupling model (energy transfer and signal transmission between the primary and secondary), and the high frequency band is based on the spatial coupling model of the radar detection target (the radar emits electromagnetic wave signals and carries the target information after hitting the target (Return to radar receiver). "Communication using reflected power" published by Harry Stockman in 1948 laid the theoretical foundation for radio frequency identification technology. Today we are going to talk about how RFID technology can be used in car anti-theft systems. 1. Overview of RFID car anti-theft system At present, the anti-theft of automobile products can be divided into four categories: mechanical, electronic, chip and network. Although each has its own advantages and disadvantages, the development direction of automobile anti-theft is toward a more intelligent chip and network. RFID car anti-theft system is a chip type anti-theft system, it is a new application of RFID. Because this is a small enough RF card that can be encapsulated in a car key and contains a specific code word. The system is equipped with a reader under the steering wheel of the car. The distance between the reader and the ignition key is less than 7 cm. When a correct key with a transponder is inserted and hit the "M" position, the car anti-theft system is powered on and read The device reads the valid UID number, the system voice prompts the key is correct, and automatically completes the code, unlocks the engine computer, otherwise the voice alarm, the engine computer is in the locked state, the engine management system (EMS) locks the oil circuit and the engine, the engine ignition and The fuel injection control is cut off, the car cannot start, and the car's central computer can easily prevent short circuit ignition and realize the anti-theft function. 2. Composition principle of RFID car anti-theft system The RFID system is the core component of the car anti-theft system. It is generally composed of electronic tag (TAG, radio frequency card), reader and radio frequency antenna. The tag is composed of a coupling element and a chip, and contains a built-in antenna for communication with the RF antenna; the reader is used to read (it can also be written in the reader card) tag information; the RF antenna is used between the tag and the reader Pass radio frequency signals. The basic working process of the system is that the reader sends a radio frequency signal of a certain frequency through the radio frequency antenna; when the radio frequency card enters the radio frequency antenna working area, an induced current is generated, the radio frequency card obtains energy and is activated, and then the radio frequency card encodes itself and other information through the card The antenna is sent out; the RF antenna receives the carrier signal sent from the RF card and transmits it to the reader through the regulator "target = _blank> regulator, the reader demodulates and decodes the received signal, and then sends it to the background The main system performs related processing; the main system judges the legality of the card according to the logic operation, and at the same time makes corresponding processing and control for different settings, and issues command signals to control the action of the actuator. 3. Hardware design of RFID car anti-theft system This RFID car anti-theft system is composed of RFID system as the core. Automobile anti-theft system hardware control unit selects Motorola (Freescale) 16-bit microcontroller MC9S12D64, radio frequency identification system consists of reader S6700, transponder TAG-IT and radio frequency antenna. In addition, the system also includes storage circuit (AT24C01), detection circuit, voice circuit and CAN bus communication circuit. The control unit microcontroller MC9S12D64 in this system continues the excellent tradition of Freescale Semiconductor in the field of automotive microcontrollers. It is based on the faster S12 core (StarCore) as the core member of the MC9S12 series microcontrollers. These two device pins Compatible, the memory can be upgraded. And there are a variety of peripheral devices to choose from. MC9S12D64 has a total of 8 working modes. The mode can be set by collecting the status of the three pins BKGD, MODB, and MODA during reset, which can enhance the selectivity of the application. The S6700 IC card read-write multi-protocol transceiver and the transponder TAG-IT form a radio frequency system. The S6700 uses a 13.56MHz operating frequency. And has an anti-collision mechanism. Because the S6700 uses Manchester encoding, it can allow multiple cards to read and write at the same time without conflict. The typical transmit power is 200mW. The protocols it supports include TITAG-IT protocol, ISO / IEC15693-2 protocol and ISO / IEC14443-2 protocol. The interface between the S6700 and the CPU is a synchronous serial interface (SPI). SCLOCK, DIND, and OUT are clock line, data input line, and data output line, respectively. The clock line is bidirectional, DOUT is used for data output during data reception, and used to indicate the status of the S6700 internal FIFO register during data transmission. The transponder TAG-IT is fully compatible with ISO / IEC15693 protocol. There are 64-bit UID (card number) and 8-bit AFI (application identification number), 8-bit DSFID (data storage format) in the card, where the UID is not modifiable. In addition, there are 2KB of EEPROM in the card, divided into 64 blocks, each block 32Bit, each block can be locked to protect the data from modification. RFID technology is still in the development stage and will be closely connected with us. As a professional RFID technology solution provider, Suzhou Xindao will be committed to promoting the popularization and development of RFID technology.
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