So I had/have a semi-old dead laptop. The motherboard is dead, everything else works. It’s a Dell XPS M1330. It has a fingerprint scanner that made my curious. How does it work? How is it connected and can I use it?
I ripped the laptop open and extracted all kinds of fun stuff including the fingerprint sensor.
It has a little chip with a writing / / TCD42A1DN0 / /
So I started investigating.
First thing that threw me off was the 6 pin ribbon cable (USB typically uses 4).
- Finding ground pin is the easiest – Found that.
- Found the power pin- It was a line that had a capacitor connected with the ground. So I assumed this was the power pin.
- Two pins are unpopulated.
- Two pins are connected to resistors – starts to seem like USB data lines~.
Typically all internal laptop stuff uses 3.3V. So that seemed a safe way to go. I need to use a voltage converter to step down from 5V.
It has a ribbon cable, so that’s a no go. Removed that and the plug and decided to connect wires directly to it.
This needs some soldering under a microscope because this stuff is tiny.
Soldered everything up and time to test.
USB data + and – //connected it randomly, 50/50 chance that it goes correctly the first time. (But in real life I connect it always backwards the first time.)
Connected it a perforated board and hooked up the USB cable.
Time to roll
Connected to a computer. Windows detected it (Data+ and Data- went right ways the first time). Windows installed drivers automatically and restarted the computer.
Voila, it is working!