Raspberry Pi RFID, PIN & fingerprint project

Hoping someone can help. I am currently doing a school project using a raspberry pi to allow RFID scanning, then a PIN entry then finally a fingerprint scanner, all fetched from an SQLite database. Eventually it will open a door lock, but for now, I’m just working on the code. But I can’t get the fingerprint scanner to work.

The rfid and PIN works fine. Used the database. Access is granted if correct credentials.

Once I try to add the fingerprint scanner, it’s just doesn’t work. The fingerprint scanner works on its own (outwith the project). I have enrolled several prints. But the moment I try it within the larger code, it states the sensor is not being read. Then even to go back to a simple loop test for the sensor, I have to reboot the pi before it works again.

I’m not sure what I’m doing wrong. I have double checked the correct serial port is in use. Bluetooth is disabled. I’m just lost.

It’s a DollaTek blue fingerprint optical reader I’m using. I also have a R307(similar) but had the same problem. Does it need an additional power source maybe? Any help appreciated.

Code so far (that keeps crashing the sensor):

import RPi.GPIO as GPIO
import time
import i2c_lcd
import sqlite3
import adafruit_fingerprint
import serial

# Define Keypad Pins
ROWS = [5, 6, 13, 19]
COLS = [12, 16, 20, 21]

KEYS = [
    ['1', '2', '3', 'A'],
    ['4', '5', '6', 'B'],
    ['7', '8', '9', 'C'],
    ['*', '0', '#', 'D']
]

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

for row in ROWS:
    GPIO.setup(row, GPIO.OUT)
    GPIO.output(row, GPIO.HIGH)

for col in COLS:
    GPIO.setup(col, GPIO.IN, pull_up_down=GPIO.PUD_UP)

# Initialize LCD - Check I2C address (0x27 or 0x3F)
lcd = i2c_lcd.lcd()

# Initialize Fingerprint Sensor
uart = serial.Serial("/dev/serial0", baudrate=57600, timeout=1)
fingerprint = adafruit_fingerprint.Adafruit_Fingerprint(uart)

def read_keypad():
    """ Reads the pressed key from the keypad """
    for row_index, row in enumerate(ROWS):
        GPIO.output(row, GPIO.LOW)
        for col_index, col in enumerate(COLS):
            if GPIO.input(col) == 0:
                time.sleep(0.1)  # Debounce
                while GPIO.input(col) == 0:
                    pass  # Wait until key is released
                GPIO.output(row, GPIO.HIGH)
                return KEYS[row_index][col_index]
        GPIO.output(row, GPIO.HIGH)
    return None

def get_user_from_db(user_pin):
    """Retrieve user information from the database using the PIN"""
    try:
        conn = sqlite3.connect('users.db')
        cursor = conn.cursor()
        cursor.execute("SELECT name, fingerprint_id FROM users WHERE pin = ?", (user_pin,))
        result = cursor.fetchone()
        conn.close()
        return result if result else None
    except Exception as e:
        print(f"Database error: {e}")
        return None

def verify_fingerprint(fingerprint_id):
    """Checks if the fingerprint matches the stored ID"""
    print("Waiting for fingerprint...")
    lcd.lcd_display_string("Place Finger...", 1)
    
    while fingerprint.get_image() != adafruit_fingerprint.OK:
        pass  # Keep waiting for a valid fingerprint scan
    
    if fingerprint.image_2_tz(1) != adafruit_fingerprint.OK:
        return False
    
    if fingerprint.finger_search() != adafruit_fingerprint.OK:
        return False
    
    return fingerprint.finger_id == fingerprint_id

try:
    while True:
        lcd.lcd_clear()
        lcd.lcd_display_string("Enter PIN:", 1)
        
        entered_pin = ""
        while len(entered_pin) < 4:
            key = read_keypad()
            if key:
                if key.isdigit():
                    entered_pin += key
                    lcd.lcd_display_string("*" * len(entered_pin), 2)
                time.sleep(0.3)

        user = get_user_from_db(entered_pin)
        if user:
            user_name, fingerprint_id = user
            lcd.lcd_clear()
            lcd.lcd_display_string(f"Hello, {user_name}!", 1)
            time.sleep(2)
            
            lcd.lcd_clear()
            lcd.lcd_display_string("Scan Fingerprint", 1)
            
            if verify_fingerprint(fingerprint_id):
                lcd.lcd_display_string("Access Granted", 1)
            else:
                lcd.lcd_display_string("Fingerprint Error", 1)
        else:
            lcd.lcd_display_string("Invalid PIN", 1)
        
        time.sleep(2)

except KeyboardInterrupt:
    GPIO.cleanup()
    lcd.lcd_clear()