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 I C 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.
2.) Connecting w/ a 5V Arduino
Before using the Arduino’s example code, make sure that the logic levels match. If you are using a 5V Arduino, you could use a dedicated logic level converter or resistors for
voltage division. Here are the minimum parts you would need to get started:
Fingerprint Scanner (GT-521F32 or GT-521F52)
Qwiic Cable
Redboard or Arduino Uno
Mini-Breadboard
Bi-Directional Logic Level Converter or 3x 10kOhm Resistors