Fingerprint Identification System Circuit Design Atlas - Circuit Diagram Reading (200)

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With the increasing application of electronic information technology, many occasions require identification or identity records for specific user groups, such as access control systems, time and attendance systems, and security authentication systems. Various technologies are used in various systems, such as the retina. Identification, face recognition, fingerprint recognition, RFID radio frequency identification applications, etc. Among them, the biometric identification method has been recognized and accepted by more and more people because of its convenience and high security. Especially the fingerprint identification technology has become one of the most widely used biometric identification technologies. Therefore, the research on fingerprint recognition system based on embedded architecture has practical significance and broad application prospects.

ARM optical fingerprint recognition system

The system uses an optical fingerprint sensor (the optical GC0307 CMOS image acquisition chip built-in from GECO Microelectronics Co., Ltd.) and the ARM Cortex M3 core STMicroelectronics 32-bit high-performance microcontroller STM32F205RE to form the functional body, using Sobel edge detection operator, Gabor Filtering, image binarization and other image acquisition and processing algorithms identify the fingerprint image, and build a small-volume embedded fingerprint recognition module. It has built-in embedded, micro-power, easy to use program interface, easy for secondary development and recognition. High accuracy, high cost performance and so on. The entire system design constitutes an integrated optical fingerprint recognition module. The module design adopts the principle of optical dark background imaging, and adds a special living body detection chip to solve the problem of residual fingerprint misidentification and rubber false fingerprint while solving the dry finger effect.

Figure 1 shows the schematic diagram of the application circuit of the optical GC0307 CMOS image acquisition chip from GECO Microelectronics Co., Ltd. This CMOS image acquisition chip is a built-in component of a high-precision, low-power, micro-volume, high-performance camera that combines CMOS image sensors for high-quality VGA images with highly integrated image processors, embedded power supplies, and high-quality The lens group is combined to output a JPEG image or image video stream, supports 8/10 digit digital transmission of JPEG images and YCbCr interface, providing a complete imaging solution.

The CMOS image acquisition core function output serial data pin, clock signal pin, reset pin, serial bus pin, etc. are all connected to the GPIO port of the STM32F205RE, and the image information acquired by the CMOS chip is read through the GPIO port analog timing. . Since the STM32F205RE's GPIO port can operate at 120 MHz, the timing can be simulated very accurately and efficiently. The original image of the measured 640 & TImes; 480 can be acquired into the main processor STM32F205RE for image processing at 10 frames/s.

Using ARM processor as the control core, the design method and process of embedded system for fingerprint identification algorithm. The system uses optical fingerprint sensor (built-in GSK Microelectronics Co., Ltd. optical GC0307 CMOS image acquisition chip) and ARM Cortex M3 core STMicroelectronics 32-bit high-performance microcontroller STM32F205RE to form the functional body, using Sobel edge detection operator, Gabor Fingerprint images are identified by image acquisition and processing algorithms such as filtering and image binarization. After repeated practice, the scheme is suitable for the development of embedded components, such as biometric fingerprint feature extraction, recognition, fingerprint identity authentication, comparison and other occasions. The system is cost-effective and easy to interact, with high recognition rate and strong scalability, which is convenient for embedded applications.

MBF200 solid state fingerprint sensor

MBF200 is an advanced solid-state fingerprint sensor introduced by Fujitsu. In addition to automatic fingerprint detection, it also has a variety of interface modes. It is a capacitive sensor. Its capacitive sensor array consists of two-dimensional metal electrodes, all metal electrodes. Acting as a capacitive plate, the contact fingers act as the second capacitive plate, and the passivation layer on the surface of the device acts as an insulating layer for the two plates. When a finger touches the surface of the sensor, the unevenness of the fingerprint creates a varying capacitance on the sensor array, causing a change in voltage across the two-dimensional array and forming a fingerprint sensing image. Capacitive solid-state device with standard C13MS technology, with 500 dpi resolution and sensor area of ​​1.28 cmxl.50 cm. With automatic fingerprint detection capability, it contains 8-bit analog-to-digital converter and can provide three kinds of bus interface. The power consumption at 5 V operating voltage is less than 70 mW. 1.2 Ethernet Interface Circuit Design The AT91SAM7X256 integrates a MAC controller internally to support the MII interface and the RMII interface. RTL820lBL is an industrial grade 10/100 Mb/s low-power Ethernet transceiver with MII interface, 25 MHz clock output, intelligent power-down mode, providing a stable and reliable high-quality network solution for the factory. And other harsh operating environments to set up Ethernet that supports real-time transmission, in line with IEEE 802.3u technical standards. The schematic diagram of the Ethernet interface circuit is shown in Figure 2.

Figure 2 Ethernet interface circuit schematic

Design of circuit module using single chip fingerprint recognition system

The fingerprint recognition sensor is used for fingerprint collection and recognition, the fingerprint is processed in the single chip microcomputer, the current fingerprint recognition state is marked by the button, the input state, the recognition state, the clear state, and the liquid crystal 1602 can display the current fingerprint recognition state information; Judging the current information, for example, reminding the current fingerprint identification error; using a buzzer and an LED to remind the current fingerprint identification is correct.

The system first collects fingerprints from the digital camera ov6620 and converts the fingerprint images into digital images. Then the 16-bit Freescale X128 single-chip microcomputer is used to preprocess the fingerprint digital image, and then through image enhancement, segmentation, smoothing, refinement, etc. The process obtains a digital image that facilitates fingerprint feature extraction: then extracts the refined image detail feature points; then sends the fingerprint information data into the STC89C52 single-chip microcomputer, and a liquid crystal 1602 is connected with the STC89C52 single-chip microcomputer, and the liquid crystal is used to display the current fingerprint collection system work. The status and the information collected by the fingerprint after comparison are correct. A buzzer and LED indicator are used to indicate that the currently collected fingerprint information is correct. When the collected fingerprint information is correct, the buzzer sounds and the LED indicator lights up.
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