Design and Implementation of Fingerprint Identification System Based on STM32 Chip

Fingerprint recognition is a technique for identifying individuals based on the invariance and uniqueness of each person's fingerprint. With the development of society, embedded fingerprint recognition technology has become more and more popular in the market and has become the focus of research and development in recent years. However, most of the current embedded fingerprint algorithms still have shortcomings in real-time and accuracy, and further optimization algorithms are needed. To achieve accurate and efficient fingerprint recognition.

This study designs and implements a fingerprint recognition system based on STM32 chip. Fingerprint data is collected by fingerprint sensor, fingerprint algorithm is used to process fingerprint data to realize fingerprint recognition, and the human-computer interaction interface is combined with VC++ platform to display fingerprint image data.

This study uses the 32-bit processor STM32F-103ZET6 of ARMcortex-M3 core as the main controller. The chip adopts Harvard architecture, which integrates 64KB of RAM and 512KB of FLASH. It has fast operation speed and small size and low power consumption. The features have a high application prospect in embedded image processing. The structure and function diagram of the fingerprint identification system is shown in Figure 1.

Figure 1 system hardware block diagram

The system hardware mainly includes: a fingerprint collection module, an SPI interface module, a fingerprint data storage module (SRAM), a fingerprint program storage module (FLASH), a UART module, a fingerprint image algorithm processing module, and a processing result display module.

The specific work flow is as follows: The system supplies 5V regulated power supply through USB, and converts it into 3.3V regulated power supply through internal circuit. After the system is powered on, the STM32 is used to initialize each register of the sensor, and the fingerprint sensor FPS200 collects fingerprint images through the SPI interface. The STM32 minimum system communicates, and the collected fingerprint data is sent to the STM32, thereby storing the fingerprint image to the SRAM, and preprocessing the fingerprint image signal, extracting feature points and image matching through various algorithms, and finally implementing the fingerprint recognition function. In addition, the STM32 and the host communicate the fingerprint image data to the PC through asynchronous serial communication, and display the image. Since the data volume of one image is 76.8 KB, the internal RAM capacity of the main control chip cannot meet the requirements for storing and processing image data, so This design extends SRAM to store fingerprint data. The system design program is placed in FLASH, and the fingerprint feature data template is also placed in FLASH, so that it can be deleted and added during use, and the fingerprint recognition result is displayed. The main controller adopts JTAG interface and performs simulation debugging through J-link. IAR-forARM implementation program design.

The collection of fingerprint images is very important for the system to realize its recognition function. A fingerprint image with better acquisition quality is beneficial to the subsequent algorithm processing of fingerprint images, reducing the complexity of the algorithm and improving the function of system fingerprint recognition.

Fingerprint sensor FPS200 is a new type of fingerprint sensor from Veridicom with 500dpi resolution, integrated 300&TImes; 256 sensor array, 256 grayscale images and 8-bit pixel data, and supports MCU, SPI and USB. Interface mode, here is a relatively simple SPI interface mode, supply 3.3V regulated power supply, the system fingerprint acquisition hardware circuit shown in Figure 2.

MODE1 of STM32 is connected to VCC and MODE0 to GND, so that it works in SPI mode and is in master mode. Fingerprint sensor FPS200 operates in SPI slave mode. Thus, the STM32 is connected to the four pins of the SPI interface of the FPS200 through the PB12~15 pins. The FPS200 performs related operations according to the command, address and command data of the write register sent by the STM32 from the SPI interface, and transmits the collected fingerprint data back to the STM32 via the SPI interface for further processing.

Figure 2 Schematic diagram of the fingerprint acquisition system

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