# GT-521F32 fingerprint sensor: specs and pinout

> An optical fingerprint module with an on-board processor and a UART interface, made by ADH-Tech. The GT-521F32 version holds 200 fingerprints. Use…

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An optical fingerprint module with an on-board processor and a UART interface, made by ADH-Tech. The GT-521F32 version holds 200 fingerprints. Use only with the consent of every person enrolled.

Every value cites its sourceOfficial pinout

[Buy on Compoden](https://compoden.com/products/gt-521f32-finger-print-sensor-module-optical-uart-compoden)

## Specs

| Spec | Value | Source |
|---|---|---|
| Operating voltage (UART module) | DC 3.3 V to 6 V | source Section 3 Specification (p.6); UART connector pin 4 VCC (p.9) |
| Operating current | Under 130 mA | source Section 3 Specification (p.6) |
| Fingerprint capacity (GT-521F32) | 200 | source Section 2 Feature (p.5) |
| Sensor and resolution | Optical sensor, 450 dpi, image 258 x 202 pixels | source Section 3 Specification (p.6) |
| UART baud rate | 9600 bps default after power on; 9600 to 115200 bps supported | source Section 3 (p.6); Section 5 UART connector (p.9) |
| UART input thresholds | VIL = 0.8 V, VIH = 2 V on TX and RX | source Section 5 Pin Assignment (p.9) |
| Matching modes and template size | 1:1 verification and 1:N identification; template 496 bytes plus 2 bytes checksum | source Section 3 (p.6); Section 2 (p.5) |
| Enrolment and identification time | Enrolment under 3 s (3 fingerprints); identification under 1.5 s | source Section 3 (p.6) |
| Error rates (maker figures) | FAR under 0.001 percent; FRR under 0.1 percent | source Section 3 (p.6) |

## Power

| | Value | Source |
|---|---|---|
| Supply | DC 3.3-6 V on the UART connector VCC pin | source Section 3 Specification (p.6) |
| Current | Under 130 mA operating | source Section 3 Specification (p.6) |

## Pinout

Pin tables are from the ADH-Tech GT-521FX2 datasheet V1.1 (July 2017), which also covers the GT-521F32 (200 fingerprints). The cable colours and connector shape of the module in hand are not covered.

| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| UART 1 TX | Transmitting serial data | VIL = 0.8 V, VIH = 2 V | | source Section 5 Pin Assignment, UART connector (p.9) |
| UART 2 RX | Receiving serial data | VIL = 0.8 V, VIH = 2 V | | source Section 5 (p.9) |
| UART 3 GND | Ground | 0 V | | source Section 5 (p.9) |
| UART 4 VCC | Power voltage | 3.3-6 V | | source Section 5 (p.9) |
| Touch 1 VDD | Touch IC power | 3.3 V | | source Section 5, Touch IC connector (p.9) |
| Touch 2 GND | Ground | 0 V | | source Section 5 (p.9) |
| Touch 3 ICPDA | Program mode in-circuit programming data/address pin | VIL = 0.66 V, VIH = 2.64 V | | source Section 5 (p.9) |
| Touch 4 ICPCK | Program mode clock pin; in normal mode goes low to high when a finger touches the metal frame | VIL = 0.66 V, VIH = 2.64 V | Usable as a wake-up signal to the MCU. | source Section 5 (p.9) |

## Build with it
Project ideas for the GT-521F32 fingerprint sensor. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.

- [Fingerprint enrolment and match demo](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20fingerprint%20match%20demo%20with%20an%20ESP32%2C%20a%20GT-521F32%20fingerprint%20module%20and%20a%200.96%20inch%20OLED): Show the matched ID number on the OLED. Everyone enrolled must give consent and be told that their print is kept on the module; keep templates on the module and do not copy them to other storage. Power the module at 3.3 V (the sheet's minimum is 3.3 V, so there is no margin) from a regulated supply that can give 130 mA; do not feed it 5 V. The sheet does not state the TX output level, so measure TX with a multimeter before connecting it to a 3.3 V RX pin. The module's UART input thresholds (VIH 2 V) work with 3.3 V logic.
- [Fingerprint-gated indicator box](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20fingerprint-gated%20indicator%20box%20with%20an%20ESP32%2C%20a%20GT-521F32%20fingerprint%20module%20and%20assorted%20LEDs): A green LED lights on a match and a red one on no match. Enrol only people who agreed and know how the print is used; templates stay on the module. Each LED needs a series resistor from the resistor pack. Power the module at 3.3 V (the sheet's minimum is 3.3 V, so there is no margin) from a regulated supply that can give 130 mA; do not feed it 5 V. The sheet does not state the TX output level, so measure TX with a multimeter before connecting it to a 3.3 V RX pin.
- [Pico fingerprint match counter](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20fingerprint%20match%20counter%20with%20a%20Raspberry%20Pi%20Pico%2C%20a%20GT-521F32%20fingerprint%20module%20and%20a%200.96%20inch%20OLED): Count how many matches happened and show it. Use only with the consent of those enrolled, and with notice of what is retained; templates stay on the module. Power the module at 3.3 V (the sheet's minimum is 3.3 V, so there is no margin) from a regulated supply that can give 130 mA; do not feed it 5 V. The sheet does not state the TX output level, so measure TX with a multimeter before connecting it to a 3.3 V RX pin. The Pico's UART is 3.3 V, above the module's 2 V input-high threshold.

## Common mistakes

- Under-powering it: operating current is up to 130 mA, so power it from a supply that can give that, not a weak pin (source: [link](https://cdn.sparkfun.com/assets/learn_tutorials/7/2/3/GT-521FX2_datasheet_V1.1__003_.pdf), Section 3 p.6)
- Using the wrong baud rate: the module starts at 9600 bps after power on; change the host to match, up to 115200 bps (source: [link](https://cdn.sparkfun.com/assets/learn_tutorials/7/2/3/GT-521FX2_datasheet_V1.1__003_.pdf), Sections 3 and 5)
- Wiring the touch connector as UART: the touch IC connector (VDD, GND, ICPDA, ICPCK) is separate from the 4-pin UART connector (TX, RX, GND, VCC) (source: [link](https://cdn.sparkfun.com/assets/learn_tutorials/7/2/3/GT-521FX2_datasheet_V1.1__003_.pdf), Section 5 p.9)

## Not covered by the official source

- The sheet is the GT-521FX2 family sheet (covers GT-521F32 with 200 fingerprints and GT-521F52); no separate GT-521F32 sheet was read.
- The sheet gives 450 dpi; the product name or page may say a different figure.
- The UART output (TX) voltage level is not stated in the sheet; only input thresholds are given.
- Operating temperature was removed from this sheet revision (revision history, V1.1).
- Command protocol is in a separate programming guide that was not read.
- Because the TX output level is undocumented, the ideas tell the builder to supply the module at 3.3 V and measure TX before connecting.

## Sources

- [link](https://cdn.sparkfun.com/assets/learn_tutorials/7/2/3/GT-521FX2_datasheet_V1.1__003_.pdf) (ADH-Tech GT-521FX2 Optical Fingerprint Recognition Embedded Module datasheet, Version 1.1, July 7 2017; verbatim copy hosted on a mirror)