Design of anti-theft remote control based on living fingerprint sensor MBF310

Introduction

　　Anti-theft remote control is mainly used in access control devices such as cars, garage doors, anti-theft doors, indoor doors, safes, etc. It can control the opening and closing of access control devices. In anti-theft mode, when the access control is illegally opened, collided, moved, vibrated, etc., an anti-theft alarm signal is issued. The fingerprint recognition anti-theft remote control on the market now uses the first generation of optical fingerprint recognition technology, which can only scan the surface of the finger skin (also known as the "dead skin layer") and cannot penetrate into the dermis. Therefore, the cleanliness of the finger surface directly affects the recognition effect. In addition, if people make a fingerprint hand model according to the fingerprint of the finger, it may also pass the recognition system. Although this fingerprint recognition technology can identify the identity of the user, it is neither safe nor stable to use. The

　　scratch-type live fingerprint reader sends an electronic signal through a capacitive sensor. The electronic signal passes through the surface of the finger and reaches the live layer of the finger skin (also known as the "dermis") to directly read the fingerprint pattern, thereby greatly improving the security of the system. Using the scratch-type live fingerprint recognition technology, the anti-theft remote control collects the user's fingerprint live layer and sends it to the remote control receiver for comparison with the legal fingerprint stored in the remote control receiver. Only when they match, the user can perform other operations on the remote control; otherwise, an anti-theft alarm signal is issued. The use of live fingerprint recognition technology to verify the identity of the user improves the system's anti-theft level, security and stability.

1 Design of anti-theft remote control transmitter

　　The scratch-type live fingerprint recognition anti-theft remote control is divided into two parts: the anti-theft remote control transmitter and the anti-theft remote control receiver. The anti-theft remote control transmitter is carried by the user, and the anti-theft remote control receiver is placed in the access control device to be protected. The anti-theft remote control transmitter uses the MSP430F12X processor as the core, and configures the working status of the scratch-type live fingerprint sensor MBF310, the wireless transmission/reception chip nRF401, the parameter configuration chip AT93C46, etc., including fingerprint data reading, fingerprint data and encrypted data wireless transmission, and wireless transmission of control instructions.

　　AT93C46 stores 256 bits of parameter configuration data for encryption calculation of the transmitted data; nRF401 works in wireless transmission mode. MBF310 uses SPI working mode and is connected to the SPI bus of the MSP430F12X processor. The MSP430F12X initializes the working state of the MBF310 sensor through the SPI bus and configures it to enable the SPI mode of FIFO interrupt. When the finger slides over the MBF310, the MBF310 collects the fingerprint data and stores it in the FIFO buffer. When the FIFO buffer is full, an interrupt signal is generated. After receiving the FIFO buffer full interrupt signal, the MSP430F12X processor immediately reads the fingerprint data collected by MBF310 through the SPI bus. The read fingerprint data and the configuration word in the AT93C46 are encrypted by "OR" operation, and the encrypted data is transmitted through nRF401, thereby realizing the functions of fingerprint collection, fingerprint data reading, encryption and wireless transmission, and wireless transmission of control instructions. The circuit connection diagram of the anti-theft remote control transmitter is shown in Figure 1.



Figure 1 Circuit connection of anti-theft remote control transmitter Figure

2 Design of anti-theft remote control receiver

　　The anti-theft remote control receiver consists of MSP430F12X processor, wireless transmission/reception chip nRF401, parameter configuration chip AT93C46, fingerprint template memory FM24C64, buttons and indicator lights. When the anti-theft remote control receiver works normally, the MSP430F12X processor selects nRF401 as the wireless receiving mode to receive the data and instructions transmitted by the anti-theft remote control transmitter in a timely manner. When receiving fingerprint data, the MSP430F12X processor uses the 256-bit configuration word in AT93C46 to decode the received encrypted fingerprint and obtain the real live fingerprint data collected by MBF310 in the anti-theft remote control transmitter. Then the decoded fingerprint data is compared with the fingerprint template data pre-stored in the fingerprint template memory FM24C64. If the comparison result is true, it indicates that the legal identity authentication is obtained, then the anti-theft remote control receiver can receive the control command of the anti-theft remote control transmitter (the command set by the button on the anti-theft remote control transmitter), otherwise it will not respond to the command data transmitted by the anti-theft remote control transmitter. The buttons of the anti-theft remote control receiver are used to establish fingerprint templates, and the indicator light indicates the current working status of the anti-theft remote control receiver. Output ports 1 to 6 are output control signals generated according to the remote control command. The circuit connection diagram of the anti-theft remote control receiver is shown in Figure 2.

 

Figure 2 Circuit connection diagram of anti-theft remote control receiver Figure

3 Application example

　　Taking this design as a car anti-theft remote control as an example, the car anti-theft remote control consists of two parts: a car anti-theft remote control transmitter and a car anti-theft remote control receiver. The car anti-theft remote control transmitter is carried by the car owner, and the car anti-theft remote control receiver is installed in the car. The three command operation buttons of the car anti-theft remote control transmitter are defined as opening the car system (KEY1), closing the car system (KEY2) and finding the car (KEY3). The output control port outputs 1 to 6 of the car anti-theft remote control receiver are defined as: alarm sounding, headlight flashing, door lock opening/closing, rear hatch opening, total circuit on/off, and car ignition/off control signal.

　　All operations of the car anti-theft remote control are based on fingerprint recognition. First, the remote control operator's finger (the remote control operator's finger that has established a fingerprint template in the car anti-theft remote control receiver) slides lightly over the fingerprint recognition window; after the car anti-theft remote control transmitter collects the fingerprint, it encrypts the fingerprint data through the encoding encryption algorithm and transmits it through the FSK method; the car anti-theft remote control receiver within the effective distance receives the encrypted data, and obtains the decrypted fingerprint data through the decoding algorithm, and then compares it with the stored fingerprint template data one by one. If the comparison result is true, the operator's identity is confirmed to be successful and the command data of the remote control transmitter can be received, otherwise the remote control transmitter's command will not be received. If the car is forcibly operated without obtaining the operator's legal identity, the anti-theft remote control receiver will send an alarm control signal (such as the alarm ringing, the headlights flashing), and execute other anti-theft control signals (such as the main circuit disconnection, the car is turned off, the door locks are closed, etc.).

Conclusion

　　The anti-theft remote control transmitter designed in this paper adopts the scratch-type live fingerprint recognition chip MBF310, which belongs to the second generation of fingerprint recognition technology. It effectively overcomes the shortcomings and deficiencies of the first generation of fingerprint recognition technology, such as low recognition rate and recognition of rubber molded fingerprints, and improves the security level and correct recognition rate. The

　　nRF401 wireless transceiver chip adopts FSK technology, and the remote control distance can reach 800 m. In the anti-theft remote control transmitter and anti-theft remote control receiver, AT93C46 is a codec configuration chip, which stores 256 bits of codec data. The remote control transmitter uses a 256-bit encoding encryption algorithm when transmitting data, which can prevent the remote control data from being intercepted and cracked and the remote control transmitter from being imitated. Only when the codec data of the remote control transmitter and the remote control receiver are the same, can the remote control operation be performed, which improves the security level. The fingerprint template memory in the anti-theft remote control receiver uses an 8 KB high-speed ferroelectric memory FM24C64, which can read and write 1 010 times without failure, and keep the data for 10 years without loss in the case of power failure. The remote control transmitter and receiver use the ultra-low power 16-bit processor MSP430F12X as the data processing and control core, which improves the data operation speed and the intelligence of the system and reduces the power consumption.

References

[1] Hu Dake. MSP430 series FLASH ultra-low power 16-bit microcontroller [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2001.
[2] Hu Dake. MSP430 series microcontroller C language program design and development [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2003.
[3] Wei Xiaolong. MSP430 series microcontroller interface technology and system-related examples [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2002.