Jack Burton, Katherine Deane, Brady Kamali

This project interfaces the Adafruit basic fingerprint sensor with the STM32L432KC using UART. It handles fingerprint enrollment and matching over UART, and uses fingerprint scanning to open a lockbox when an authenticated fingerprint is scanned.

An attached Analog Discovery 2 (AD2) monitors the UART traffic using UART Spy mode. A helper script (Match_detect.js) detects when a successful fingerprint match occurs by identifying the signature 0x07 0x00 0x07 0x00 in the fingerprint sensor response packets and sets an output pin (DIO6) high. We then drive a servo motor to rotate and open the lockbox.

Platform: PlatformIO
Board: ST Nucleo-L432KC
Framework: CMSIS
Peripherals: Adafruit Optical Fingerprint Sensor (Product 4690), High Power, High Torque Micro Servo
External Tool: Analog Discovery 2 (AD2) with WaveForms

• main.cpp — Embedded code to enroll fingerprints and match prints continuously, contains custom function to write UART command packets conforming to fingerprint sensor documentation. Controls a servo to open/close upon matching fingerprint.
• timer.cpp, uart.cpp, gpio.cpp — Low-level CMSIS helper libraries (UART, GPIO, and PWM configuration).
• Match_detect.js — WaveForms script to monitor UART, detect fingerprint match, and toggle DIO6.

• STM32 talks to the fingerprint sensor over USART1 at 57.6k baud using packet structures outlined in the documentation.
• Upon a matching fingerprint, the sensor sends an ACK packet containing successful match sequence (0x07 0x00 0x07 0x00).
• AD2 spies on the UART line between STM32 and sensor.
• Match_detect.js listens for the success sequence. When detected:
  • DIO6 is set HIGH (or Wavegen1 Channel 1 is turned ON) for 5 seconds.

1. Flash the Board

   • Open the project in PlatformIO.
   • Build and upload to nucleo_l432kc board.

2. Hardware Connections

   • Connect the fingerprint sensor UART (TX/RX) to the Nucleo (PA9/PA10).
   • Use Analog Discovery 2 to spy on the UART line, by connecting DIO1/PIO0 to PA9/PA10 on the Nucleo. Connect DIO6 on the AD2 back to the input pin on the Nucleo.
   • Connect the servo's power to an external power supply (NOT 5V on the Nucleo, it will fry the board!), its logic to the specified logic pin on the Nucleo, and its ground to the Nucleo ground.

3. Run Detection Script

   • Open WaveForms → Protocol → UART Spy.
   • Set: Baud: 57.6k, Parity: None, 8 Bits, Polarity: Standard.
   • Open Wavegen, and configure an appropriate output voltage to perform the desired function on fingerprint match.
   • Load and run Match_detect.js.
   • Watch DIO6 (or Wavegen Channel 1) toggle high on fingerprint match, causing the servo to rotate.

• Clone or download this project.
• Open it in PlatformIO.
• Confirm the following PlatformIO settings:

[env:nucleo_l432kc]
platform = ststm32
board = nucleo_l432kc
framework = cmsis

Thank you to my friend and housemate Ege Ozgul for his help with debugging and loaning his AD2/power supply.

Thank you to @btdat2506 for translating the documentation to English. Could not have done it without that!