Design of security door lock for fingerprint identification based on ATMEGA32

0 Preface

Human biological characteristics are inherent physiological characteristics and behavioral characteristics of the human body, such as fingerprints, palm prints, facial images, iris, retina, voice, signature, gait and so on. These features are portable, so easy to use, not easy to forget or lose, the human body's biological characteristics and the human body is the only binding, and has a unique nature of everyone, so the security of good, not easy to forge or stolen. Therefore, the use of human biological characteristics to replace the traditional method to identify the person's identity is a recognition of the identification of the object is a direct verification method, is clearly the most safe and reliable, which is also the needs of modern social development.
With the development of Optoelectronics and other science and technology, human biometric identification is a very practical and high-tech technology has also been greatly developed and applied. Among them, the development of fingerprint identification technology is the most mature, the earliest and most widely used. Because each person's fingerprint of the pattern, breakpoints and intersections are different, so its fingerprint characteristics are unique, and lifelong unchanged. Relying on this uniqueness and stability, we can match a person to his fingerprints. A lot of fingerprint sensor module appears , This paper designs a MRB200 fingerprint recognition module based on ATMEGA32 as core processor, using Shanghai one-dimensional company. This fingerprint identification module can be run independently (running from PC), the whole system has the advantages of low cost, simple application and easy development.

1. Control scheme Design

System functional Block Diagram 1

Figure 1 System functional block diagram

The fingerprint identification door design with single-chip microcomputer as the core, through the MRB200 Fingerprint Module acquisition System acquisition fingerprint data, the specific scheme is: Touch fingerprint sensor When the system entered the fingerprint contrast state, by the CPU through the serial port to send a comparison command to the Fingerprint identification module, The fingerprint recognition module receives the CPU sends the command to begin to collect the user fingerprint, and will collect the fingerprint data and the fingerprint database all fingerprint carries on the one by one contrast, if has the same then returns the comparison success message to the CPU, the fingerprint recognition module collects the process to carry on three times, the Fingerprint identification module will return each sample result, CPU record three times the number of successful acquisition, such as three times are collected successfully, the CPU will drive the buzzer rang, tell the guest's fingerprint by contrast, while the CPU through the drive circuit control electric lock open door lock. Buttons and displays are used for fingerprint management.

2. System Hardware Design

The system uses ATMEGA32 as the control core, the control system mainly includes MRB200 fingerprint identification Module , liquid crystal display, set button, electronic lock, buzzer and other parts.

System Hardware Design 2

Figure 2 System Hardware design diagram

This design adopts Atmel's AVR MCU ATMEGA32 as the control core. The single-cycle instruction of AVR MCU can guarantee high execution efficiency and low cost, and is a high-performance device in the CPU of thin instruction set. AVR microcontroller can provide up to 16MIPS of execution time, with 32K bytes of programmable flash memory, while having 2K bytes of static RAM. The AVR microcontroller comes with watchdog timer, which can prevent the program from running and flying under the condition of strong electromagnetic interference. The Atmega32 used in this design also has the following features:
(1) The internal contains a hardware multiplier, speed multiplication speed, I/O port pin number up to 23;
(2) Support on-line programmable function, do not need to frequently from the board to Plug and unplug the chip, with programmable support synchronous transmission of the UART port;
(3) Support three-wire transmission SPI port, with convenient i²c bus port;
(4) Support JTAG boundary scan circuit, with BOD low voltage detection function;
(5) A/D converter with 8-way 10-bit internal, with 4 PMW, can work together or alone;
(6) Internal real-time clock circuit, operating frequency up to 16MHz.

description of communication interface between CPU and MRB200 fingerprint identification Module

MRB200 vin pin power positive input termination 4~6.5v,500ma;sleep foot sleep state control (Low: Power off the module, high so that the module is in a normal power state, power up 600ms after the normal operation) and the CPU O feet connected Fingeron Foot Acquisition Status flag (Low: No fingerprint acquisition, high fingerprint acquisition in progress) and the CPU I foot connected The TX pin asynchronous serial output (3.3V logic level) is connected to the RX pin of the CPU, and the RX (3.3V logic level) PIN asynchronous serial input is connected to the CPU's TX PIN, and the gnd of the two chip is connected directly.

CPU and fingerprint module communication for half-duplex asynchronous serial communication, the CPU through the serial port and fingerprint identification module to communicate, complete the fingerprint entry, deletion, identity confirmation, through the verification to drive the circuit to control the door lock to perform the action of the switch door.

In order to adapt to the communication rate of different CPUs, the communication rate of this fingerprint identification module is 19200BT/S, or it can be set to (9600 bt/s 19200 bt/s 38400 bt/s 57600 bt/s, 115200 bt/s), the transmission frame format is 10 bit, 1 bit starting bit, 8-bit data bits, 1-bit stop bits, no parity-parity bits.

Fingerprint identification module is divided into photoelectric inductive and piezoelectric induction type two, photoelectric induction type basic working principle: the light source emits a group of light, through the full reflection prism has been the angle of the finger fingerprint of the glass surface, the reflection of the light through the prism of another right angle projection to the CCD or CMOS semiconductor photoelectric imaging device. Because the ridge and the valley of the finger fingerprint are different from the light, the output signal of CCD or CMOS photoelectric imaging device is changed with the change of the finger fingerprint image, and the digital fingerprint image information is output by video amplification and A/D conversion. The piezoelectric inductive working mechanism is based on the different pressure sense of the finger fingerprint, using the top surface of the semiconductor pressure sensor array is elastic pressure sensitive media material, when the finger presses on it, according to the finger fingerprint of the outer ridge line of the size of the bump pressure into the corresponding electronic signal, and then form a fingerprint image. Because the former is limited by the optical path, the size of the distortion collector is large, and the latter is easy to integrate into all kinds of identification application products because of its thin thickness, large acquisition area, low power consumption and cost. Now product developers are increasingly inclined to the latter.

The system uses Shanghai one-dimensional Technology Co., Ltd. MRB200 piezoelectric inductive fingerprint sensor, it is a small size, strong sense of the fingerprint sensor, MRB200 fingerprint module using high-speed DSP as the core processor, it is a can store 500 fingerprints of the independent collection of module, Mainly by the Fingerprint acquisition unit and the fingerprint Processing Unit are composed of two parts. Fingerprint acquisition system is mainly responsible for collecting fingerprint image and transmitting to fingerprint processing unit. The fingerprint processing unit completes a series of operations based on commands from an asynchronous serial communication port. such as fingerprint matching, fingerprint registration, fingerprint deletion. The Fingerprint Processing unit provides an interface to the Fingerprint acquisition unit and an asynchronous serial communication port connected to the external control system. Using the control instructions provided by the MRB200 module, users can develop their own powerful fingerprint identification applications without the need for fingerprint identification expertise. The Fingerprint Identification module communicates with the external data through the serial port

Because the system is offline operating system, for user-friendly use, the system set up 4 keys and small LCD display:

Fingerprint management via key and presentation procedures:

(1): Fingerprint input: Through the keys and liquid crystal display prompts to register the user fingerprint, in consideration of the confidentiality of fingerprint entry, in the registration of fingerprints, you need to enter the administrator password or Administrator fingerprint login management interface, before the fingerprint input, and display the fingerprint ID number, every successful entry of the buzzer will ring a sound.

(2): Fingerprint screen removal: through the key and LCD display prompts to enter the administrator password or the Administrator fingerprint login management interface, into the screen in addition to the user fingerprint directory, enter the fingerprint ID number (if you do not know the ID number can be queried by the ID number of its own ID number), you can screen the ID number of the fingerprint.

(3): Query fingerprint ID number: Through the key and LCD display prompts to enter the administrator password or first with the Administrator fingerprint login management interface, enter the fingerprint ID number query directory, the finger is placed with the recognition head, fingerprint identification Module acquisition fingerprint information and fingerprint database comparison and the corresponding fingerprint ID number through the liquid crystal display.

Buzzer: Beeper is used to alert the user whether the operation is successful or to send a message and alarm.

Electronic Lock: Central control Drive voltage 12V (because the single-chip microcomputer has very limited driving capacity, so the amplifier circuit is used to drive the output of single-chip microcomputer to drive amplification).

3. System Software Design

This system software design adopts the structure and the modularization design method, facilitates the function expansion, this system software design uses the C language to write. The program module includes: Main program, fingerprint acquisition, fingerprint ratio equivalence.

The function of the main program: After the system starts or resets, the system hardware and software running environment needs to be initialized, which is done by the initiator, including MRB200,ATMEGA32 and so on initialization. When the system is powered up, the ATMEGA32 is set up via serial communication, initializing the I/O port of the CPU and opening the on-chip watchdog. Enter the main program, Scan button is triggered, if there is a button trigger to enter the fingerprint management interface (input, screen, check fingerprint operation function). If the key trigger code is not scanned to determine whether there is fingerprints on the fingerprint identification head (through the serial port to the Fingerprint identification module to send commands obtained), such as no fingerprint of the whole machine into hibernation, if there is a fingerprint through the serial port to send fingerprint capture command, (Fingerprint identification module will automatically collect the fingerprint data and fingerprint database fingerprint one by one contrast and automatically send the comparison results information to the CPU), such as successful comparison of the second same process comparison, until three times the comparison is successful the CPU through the drive circuit control electronically controlled lock to open the door lock. If one of the comparisons fails, the comparison process exits.

Low-power design of the system: After the initialization configuration is complete, wait for the user's requirements, this time to save power, you can put the system into a low-power state, such as the CPU into the power-saving sleep mode. Once the user has the input, the system exits the low power state, enters the normal execution state, controls the software to judge the user's demand, executes the corresponding function.

System main program software Flowchart 3 is shown

Figure 3 System main program software flowchart

4. Conclusion

This article uses the excellent cost-effective fingerprint identification Module MRB200, designed an anti-theft fingerprint lock , small volume, stable performance can be high, in addition to provide a convenient fingerprint door, but also provide a doorbell and a variety of alarm functions: such as the use of illegal means to open the system "illegal door alarm", Power-down system to "power off the alarm", fingerprint door lock when illegal disassembly system for "illegal disassembly" alarm.

Innovation point: This paper designed a single-chip microcomputer ATMEGA32 and MRB200 fingerprint identification module of anti-theft door lock (traditional fingerprint recognition system is mainly based on PC as the host computer development system), in product design directly using professional manufacturers of functional modules, not only can increase product function, It can also save development cost and shorten development cycle. The system has a small appearance, stable working performance, suitable for the financial, insurance, securities industry, information industry, security industry, such as the need for identification of the occasion.

The electronic design of the product price of 20000 yuan, due to its wide application, especially in the security industry, and the current on the one hand real estate (housing prices with nearly two-digit rise and economic growth almost flat) heat, on the other hand, the general public, the urgent expectation of security, because of the unique fingerprint identification, anti-counterfeiting, not easy to forge or decided that it occupies a place in the vast real estate security, it can be said that the market demand is considerable, annual sales of 2000 sets, the project annual economic benefits of 4 million yuan.

Design of security door lock for fingerprint identification based on ATMEGA32