Hi, I am currently embarking on a project requiring the fingerprint scanner to connect to the Arduino pro mini. I’m trying to use FPS_Blink.ino to initialize the fingerprint scanner. When I do so, I go to check the Serial Monitor and there is nothing being output besides FPS Open and FPS Send. There is no LED turning on either. I’m currently using the latest version of the Arduino Pro Mini, which is 3.3V as well and the code is able to be compiled properly, so I ruled it out as a problem. I’m also not utilizing a breadboard and have connected the Qwiic Breadboard Jumper Cable from with female pin header cables attached to the male pins on each color wire. I have RX TX crossover done and the Fingerprint Scanner connected to ground. I’m not sure if there is a voltage or hardware problem, and I’m not sure if the right pins are being connected and if I can only use a breadboard to connect them.
Share a photo/diagram of the wiring
Solder Joints
You should be able to connect the fingerprint scanner to an Arduino Pro Mini 3.3V/8MHz without a breadboard. It’s just a smaller version of the Arduino Uno and RedBoard. Since the system voltage is 3.3V, you don’t need a logic level converter. If you soldered headers to the Arduino Pro Mini, make sure your solder joints are ideal and sufficiently connecting to the Arduino Pro Mini => https://learn.sparkfun.com/tutorials/sp … der-joints.
If you used water-soluble flux, make sure to remove any remaining flux residue from the solder joints as well using a Q-tip and isopropyl alcohol/water. This can cause problems with serial communication sometimes => https://learn.sparkfun.com/tutorials/sp … ux-residue.
Fingerprint Scanner
The fingerprint scanner has two ports. Make sure that you are connecting to the UART port => https://learn.sparkfun.com/tutorials/fi … e-overview. To see if your fingerprint scanner is working, you could also connect it directly to a 3.3V USB-to-Serial converter and test out the sensor using the demo software. You should already have one since you need to upload code to the Arduino Pro Mini 3.3V/8MHz.
Wiring Diagram
I agree with TS-Russell. There is not enough information in your initial post to troubleshoot the issue. Sharing the pin connection and clear images of your wiring might be able to help diagnose the problem.
Here is the Schematic. I am trying to connect the Fingerprint Scanner through the RX TX and GND pins.
I am a bit confused by your diagram. The wiring doesn’t show power connected to the Fingerprint Scanner. Also, make sure to check your connections. If you check the tutorial connections and example code, the examples connect the Fingerprint Scanner’s TX to an Arduino’s Software Serial RX (pin 4) and vice versa for the Fingerprint Scanner’s Rx pin => https://learn.sparkfun.com/tutorials/fi … are-hookup. You would bypass the logic level converters with the Arduino Pro Mini 3.3V/8MHz like so :
Fingerprint Scanner (Pin #) <=> Arduino Pro Mini 3.3V/8MHz
=================================================
UART_TX (3.3V TTL) (Pin 1) <=> RX (pin 4)
UART_RX (3.3V TTL) (Pin 2) <=> TX (pin 5)
GND (Pin 3) <=> GND
Vin (3.3V~6V) (Pin 4) <=> 3.3V
The reason why we are using Software Serial is because we are not able to have 2x UART devices on the same port due to bus contention => https://learn.sparkfun.com/tutorials/se … n-pitfalls.
If that does not work, try sharing your physical image of your wiring and the solder joints. Make sure that it is clear and easy to see.
No Power
Looking at the image and from your description, that seems to be one of the problems. While you are connected to the correct port, you are not powering the Fingerprint Scanner correctly. The Fingerprint Scanner requires power to operate as indicated shown in the hardware hookup examples. Make sure to connect 3.3V as explained earlier in my post.
Software Serial
The example code in the tutorial uses Software Serial pins since there is a Serial output being sent through the Hardware Serial pins to the USB-to-Serial converter. This is the other problem that I see. Make sure to connect to the Software Serial pins as explained earlier in my post.
Other Observations
The [Arduino Pro Mini 3.3V/8MHz doesn’t look like the official version that we sell on our storefront. Make sure that it is 3.3V instead of a 5V. It looks like you connected the pins correctly with the USB-to-Serial Converter though. The headers are hard to see in the image but it looks like they are soldered sufficiently.](https://www.sparkfun.com/products/11114)