Design of circuit module of fingerprint recognition system based on ARM9

　　The working principle of biometrics is to use biometric devices to sample biological features, extract their unique features and convert them into digital codes, and further form these codes into feature templates. When people interact with the identification device for identity authentication, the identification device obtains their features and compares them with the feature templates in the database to determine whether they match, thereby deciding to accept or reject the person. Among the many biometric technologies used for identity authentication, fingerprint recognition technology is currently the most convenient, reliable, non-invasive and inexpensive solution.

　　Fingerprint recognition technology mainly involves four functional modules: reading fingerprint images, extracting features, saving data and comparing. The fingerprint reader reads the image of the human fingerprint, then preliminarily processes the original image to make it clearer, and then uses the fingerprint recognition software to establish the fingerprint feature data. The software finds data points called "nodes" on the fingerprint, that is, the coordinate positions of the bifurcation, termination or circle of the fingerprint pattern. These points have more than 7 unique features at the same time. Usually there are an average of 70 nodes on a finger, so this method will generate about 500 data. These data are usually called templates. Through the computer fuzzy comparison method. Compare the templates of two fingerprints, calculate their similarity, and finally get the matching result of the two fingerprints.

　　Ethernet interface circuit module

　　AT91SAM7X256 has an integrated MAC controller that supports MII and RMII interfaces. RTL8201BL is an industrial-grade 10/100 Mb/s low-power Ethernet transceiver with MII interface, 25 MHz clock output, and intelligent power reduction mode. It can provide a stable and reliable high-quality network solution for the system, and build an Ethernet that supports real-time transmission for factories and other harsh operating environments, in line with IEEE802.3u technical standards. The Ethernet interface circuit schematic is shown in Figure 2.