Fingerprint R502 not detected, UART voltage?

[p0cale]

Hi,
Crow R502A fingerprint sensor is not detected by Arduino.

I followed instructions and example code found at:

Interfacing R502/R503 Capacitive Fingerprint Sensor with Arduino

The physical wiring match the example and datasheet for sure. I have tried running UNO and Mega with various Soft serial pins. have tried the Adafruit library examples too. No luck.

Now i noticed the R502 by all found datasheets expect 3.3V at UART interface. However, the example on the link above runs straight TX/RX wires between Arduino 5V data-pins and FP-sensor. Is the sensor now toasted running 5V UART, though? (i constructed voltage dividers later...)

Any experience, tips, help are greatly appreciated and welcome in order to get the gadget up.

Thanks.

[xfpd]

Datasheet says:

Hardware connection
Via serial interface, the Module may communicate with MCU of 3.3V or 5V power: TD (pin 3 of P1) connects with RXD (receiving pin of MCU), RD (pin 4 of P1) connects with TXD (transferring pin of MCU). Should the upper computer (PC) be in RS-232 mode, please add level converting circuit, like MAX232, between the Module and PC

R503_datasheet.pdf