This system integrates several key components, including a fingerprint module, a MicroSD card reader/writer module, a PCF8563 real-time clock module, a buzzer, a matrix keypad, an LCD1602 display, and the STC90C516RD+ microcontroller.
System Block Diagram
The FPM10A optical fingerprint module is used in this system. It is a well-known and reliable optical fingerprint sensor with stable performance and wide application. It can be connected via TTL serial or USB interface and is compatible with 51-series microcontrollers. This module is ideal for capturing and matching fingerprint images efficiently.
2) Storage ModuleSolution 1: EEPROM Module
Although the EEPROM module is simple to use and communicates via I2C, it has limited storage capacity and a short lifespan. It also lacks expandability, which makes it unsuitable for long-term data storage. Therefore, it was discarded from the design.
Solution 2: MicroSD Card Reader Module
The MicroSD card reader uses the SPI communication protocol, which offers larger storage capacity compared to EEPROM. It is also widely used in embedded systems and provides more flexibility for future expansion. Since the system requires storing multiple fingerprint records and timestamps, the MicroSD card was chosen as the primary storage solution.
3) Real-Time Clock ModuleThe PCF8563 module is used for timekeeping. Compared to the DS1302, it offers better stability, higher accuracy, and lower power consumption. This makes it an excellent choice for applications that require precise time tracking without draining the system’s power resources.
Programming and Design IdeasProgram Flowchart
The system supports various functions such as check-in, adding fingerprints, deleting individual fingerprints, searching for fingerprints, and clearing all data. After a successful check-in, the system stores the timestamp in the corresponding sector of the MicroSD card and triggers the buzzer to confirm the action.
For function selection, a 4-button matrix keypad is used, allowing the user to navigate through options in a loop. To add a new fingerprint, the system captures two fingerprint images, stores them in buffers, and then generates a feature template. This template is saved under a specific ID, and the corresponding sector on the MicroSD card is initialized.
To delete or search for a fingerprint, the system uses two methods: entering an ID manually via the keypad or scanning the fingerprint to find its ID. The system checks whether the ID exists and whether it is currently in use by checking a flag bit stored in both the fingerprint module and the MicroSD card. Once a valid ID is found, the system displays the associated check-in time.
Clearing a fingerprint involves erasing the record from both the fingerprint module and the corresponding sector on the MicroSD card, ensuring that no residual data remains. This approach ensures secure and efficient management of user data within the system.
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