fingerprint

https://learn.sparkfun.com/tutorials/fingerprint-scanner-gt-521fxx-hookup-guide

Hardware Overview

Features

The GT-521F32 and GT-521F52 have a lot in common with the previous models. They have the same protocol commands and packet structure. Code that was implemented for previous models should be functionally the same. The fingerprint scanner has the ability to:

• Enroll a Fingerprint
• Identify a Fingerprint
• Capable of 360° Recognition

However, there are a few differences in the boards. These include:

• Different Board Layout
• 4x Mounting Holes
• 2x JST SH Connectors
• Touch Interface

One significant difference to keep in mind when integrating the fingerprint scanner in a project is the number of fingerprints that the device can hold. The GT-521F32 costs less but it can hold only 200 fingerprints. The GT-521F52 is slightly more expensive but it can hold 3000 fingerprints.

Technical Specs	GT-521F32 / GT-521F52
CPU	ARM Cortex M3 Cortex
Sensor	optical
Window	16.9mm x 12.9mm
Effective Area of the Sensor	14mm x 12.5mm
Image Size	258x202 Pixels
Resolution	450 dpi
Max # of Fingerprints	200 / 3000
Matching Mode	1:1, 1:N
Size of Template	496 Bytes(template) + 2 Bytes (checksum)
Serial Communication	UART (Default: 9600 baud) and USB v2.0 (Full Speed)
False Acceptance Rate (FAR)	< 0.001%
False Rejection Rate (FRR)	< 0.01%
Enrollment Time	< 3 sec (3 fingerprints)
Identification Time	<1.5
Operating Voltage	3.3V ~ 6Vdc
Operating Current	< 130mA
Touch Operating Voltage	3.3Vdc
Touch Operating Current	< 3mA
Touch Standby Current	< μ5

The image below shows the fingerprint scanner’s optical sensing area where the device will be able to scan your fingerprint.

There is a marking next to the JST-SH connector that indicates polarity. The JST-SH connector breaks out the pins for serial UART and power. While the input voltage is between 3.3V and 6V, the UART’s logic level is only 3.3V. You will need a logic level converter or voltage divider to safely communicate with a 5V device.

Note: Make sure that you are connecting to the correct JST connector indicated by the polarity marker and capacitors. The JST connector on the other side of the board are not connected to the same pins for serial UART.

The GT-521F32 and GT-521F52 have the ability to sense if a finger is placed on the optical sensing area. Upon contact with the metal frame around the optical sensing area, the ICPCK will output 3.3V (HIGH). Otherwise, the ICPCK will be 0V (LOW)

Touch State	ICPCK Pin Status
Finger Initially Touching the Frame	LOW => HIGH
No Finger Touching	LOW => LOW
Finger Touching the Frame	HIGH => HIGH
Removing a Finger From the Frame	HIGH => LOW

Note: If the fingerprint scanner is powered from the UART side, you will need to still provide 3.3V to power the touch interface. The GND is connected to GND plane.

Hardware Hookup

The fingerprint scanner requires a serial UART connection and power. There are a few options to connect to the sensor depending on what UART device you are using. The easiest would be to use an FTDI but you can also use any microcontroller that has a UART.

1.) Connecting w/ a 3.3V FTDI

Option 1: Qwiic Cable

To connect the fingerprint scanner to your computer, it is recommended to connect the JST SH cable to a USB-to-serial converter. Here are the minimum required parts you would need to get started:

• Fingerprint Scanner (GT-521F32 or GT-521F52)
• Qwiic Cable - Breadboard Compatible
• 3.3V FTDI Basic Breakout
• Mini-B USB Cable

Below are the following connections you would need to make with the JST-SH connector labeled as J2:

Fingerprint Scanner [Pin #]	FTDI 3.3V
UART_TX (3.3V TTL) [Pin 1]	RX
UART_RX (3.3V TTL) [Pin 2]	TX
GND [Pin 3]	GND
Vin (3.3V~6V) [Pin 4]	3.3V

After connecting, the setup should look like the image below.

Note: The colors of the Qwiic Cable are standard for I²C connections, not UART, so the colors will not match typical standards for colored cables. For example, the red wire in this circuit connects Rx to Tx. Double check your connections before powering the scanner.

Option 2: Making a Custom Adapter

If you are using the JST SH Jumper 4 Wire Assembly instead of the Qwiic cable, it is highly recommended that you make a custom adapter by soldering to the ends of the wire for a secure connection. This will ensure that the connection is not loose when inserting it into female header sockets of an FTDI or the RedBoard/Arduino Uno. The cable wire is small compared to the female header socket. A small bump can mess with the serial UART or power between the fingerprint scanner and converter. This may require you to reconnect the scanner to your computer or device. Making an adapter will also provide quick access to the small 4-pin JST-SH connector that is on the scanner.
For more information on how to make a custom adapter, please refer to the older tutorial. Remember, the pin locations are the same so the adapter can work with the current fingerprint scanner.