UPDATE:
Best compliment ever! I showed my eee PC 900 with fingerprintreader and mentioned that I built it into the machine myself. She refused to believe me! I repeatedly told her that I built it in, but she still refused to believe me! I went online and showed her this thread with pictures, step by step, and she refused to believe me! The final picture convinced her because it showed my cat Natalie and the eee PC with fingerprintreader both on it.

Original post:
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Hello again,

As promised, the continuation of my journey into breaking the eee PC 900 in interesting and novel ways. I hope it is not against forum policy to post so many pictures, but at least they're hosted off-site, so I hope it's okay. They do provide a lot of good information for people wanting to modify their own eee PC 900's.

The first picture shows the standard swipe-style fingerprintreader that I used. It is the Eikon digital privacy manager which comes with a software package by Upek. I prefer the Upek package over most other fingerprintreader packages I've seen so far because it allows me to assign applications to fingers, login at windows, it has some linux support and it tracks my passwords for websites in both IE and Firefox (though not Firefox 3.0 yet - they're working on that at the moment). The device's outward appearance makes it seem rather bulky, but the actual electronics inside of it are really quite small.


I pried the casing open with a flatheader screwdriver and found the embedded electronics and took them out. The first thing you should notice about the wires is that there are 5 of them instead of the usual 4 for USB, but that's because the fifth one is just grounding. You don't necessarily need to connect it, but you can if you want. The second thing you should notice is that the order of the wires is wrong. The usual order of the colours is red white green black. This one has the d+ and d- of the USB pins reversed, so it now is in the order of red green white black. So I had to make sure I switched the d- and d+ wires when I soldered this device to my Asus eee PC's main PCB.


I wanted the fingerprintreader in the area left of the touchpad, so I took the eee PC apart and found some sort of shielding there. There are no electronics behind this part of the shielding, but there is something there, some kind of foam, which I suspect is there to make the eee PC sound less plasticky and less hollow when tapped on. Makes it seem more solid. Kind of like old telephone handsets had a big piece of metal in it because it made the phone 'feel' like it had 'quality'. I could be wrong, though Anyways, I pried it open gently.


There are these little plastic round tabs that stick out - they were in my way so I had to remove a few of those to fit the chip in. I couldn't remove the piece of shielding entirely because it's stuck very firmly to the rest of the shieldingparts. So I just folded it over to make room to work.


I made a bit of a rough sketch of where I wanted the reader to show up. I had the smartness to think of which way to mount the reader, since it only reads fingerprints in one direction Could be kind of annoying if you mount it wrong and you have to 'swipe forward', so to speak.


I drilled some 4mm holes in the cover. Painful moment as now I knew there was no going back. The fingerprintreader bar in my fingerprintreader is ~ 17mm long and ~5mm wide, so I took a mm margin so I had some room to work with when filing the rest of the area down to just the right size. The plastic is rather thick, about 2 to 3mm.


After an hour of carefully filing the area down to a large enough size to accomodate the fingerprintreaderbar I finally managed to squeeze it in. You can see that the plastic of the cover is rather thick - the reader is sort of sunk down about a millimeter. The edges were sharp so I filed them down to create a small bevel. It doesn't need to be perfectly flat - once you put your finger on it, the skin of your fingertips sort of sinks down into the beveled slot a little. No problem at all and there's no need to press hard or anything. No sharp edges anymore either after I filed it down. This picture shows what it looked like before I created the beveled edges.


Because I filed it down gently I made it possible to actually have to squeeze the fingerprintbar into place - it keeps itself into place now. It's stuck. But, I wanted some more certainty that it wouldn't just plop out once I started using it so I drew two lines of hot glue along the edges.


To connect the reader I needed to use a USB port. The eee PC 900 has, like most eee PC models, 2 unused USB ports in the mini-PCIe ports. If your model has only one mini-PCIe port, that's okay. The electronics to connect the USB ports are very likely still there, but the connector just isn't soldered on. So just use the 8th and 9th pin (counted from the left if you look at the picture below) and there you have your USB data pins. In my eee PC 900 I have a mini-PCIe port that is taken up by the wifi card (just visible at the top of this picture, with the yellow tape over it) and a mini-PCIe port that is taken up by the 16GB add-on flashcard. (4GB onboard SSD, 16GB add-on card SSD = 20GB) The important thing is that both mini-PCIe ports have data- and data+ ports for USB connectivity, but the wifi and SSD cards are not using them. So you can use them without losing functionality. In this picture I temporarily removed the SSD card to solder the wires and to make a photo of it to show you. In this picture, the 8th mini-PCIe pin, counted from the left, is the data+ wire. The 9th pin, to the right of it, is the data- pin. As you can see, I did not solder them to the pins of the mini-PCIe connector. That's because the two contacts points I have used are connected to those pins on the PCB, and I didn't want to risk unsettling or damaging the mini-PCIe slot itself. But you can solder them to the mini-PCIe connector itself (pin 8 and 9) or if you don't have the mini-PCIe connector, just use the empty spots on the PCB to solder the wires on to. At the moment I have the mini-PCIe USB ports on the Wificard's mini-PCIe port hooked up to my bluetooth module, and I have these mini-PCIe USB ports on the SSD add-on card's mini-PCIe port hooked up to the fingerprintreader.


Yeah, I'm not too proud of these wires running around, but eh.. it does the job and it works. As you can see I placed the SSD add-on card back into it's mini-PCIe slot. The soldered wires from the previous picture are hidden underneath that add-on card (the left one. the right card is the memorycard)


And then... I totally blew it. I had my bluetooth module drawing 5volts power from the same port that the webcam draws its power from. That worked fine. Apparently though some people had problems with the webcam not working anymore because the bluetooth module was pulling too much power from that powersupply so.. I thought.. let's try another 5v trace. I found one, or so I thought, and shorted out a piece of SMD electronics on the main PCB. Nothing serious, but my webcam port, left USB port and bluetooth module were all out at the same time. The item I blew was fortunately a very simple piece of electronics that the eee PC can do without just fine. There's probably some very technical reason why that item is there, but I decided not to be technical and I removed the dead part so the shortcircuit would disappear and my USB ports would function again. Then I soldered the bluetooth module and the fingerprintreader all to the same 5volt trace that the webcam uses to get its power. In the picture below you can see the wire that goes to the fingerprintreader (going down) and the wire going to the bluetooth module (going to the right). Where they are soldered together is the webcam's 5volt trace. The contactpoint to the right of it (between the soldered wires and the black IC) used to be connected to the same contactpoint that the soldered wires are on by what is, I think, an SMD capacitor which, I also think, was designed to filter out 'noise' from the powersupply to the webcam. I had to remove it because it was causing a shortcircuit. I don't have one spare, so, whatever. The webcam works, the bluetooth works, the reader works. Even after hours of stresstesting. In any case, there are no discernible adverse effects AND it was caused by my own stupidity for having connected the fingerprintreader to a wrong trace elsewhere on the main PCB. Had I connected it here in the first place, everything would almost certainly have been fine. In case you're wondering, my bt module takes ~200ma and my fingerprintreader ~100ma. Only leaves 200ma for the webcam (assuming there is a 500ma cap on this supply trace), but as I said, things are working great so far.


I needed a ground for the reader, and since I had already used the ground before for my bluetooth module when I had it connected close to the touchpad (i moved it to the VGA port due to bad bluetooth reception) I decided to use the same bluetooth connector ground again. On the main PCB of the eee PC 900 you will find the BT_CON text next to a row of unused contactpoints. Probably it is in use in the new eee PC 901 with built-in bluetooth. In my case, I just needed the ground so I hooked it up... right there;


I used some of my colourful and haute couture yellow plastic tape to cover the exposed area of the fingerprintreader so there would be little to no chance of a short circuit. Then I folded the shielding back and molded it somewhat back into its original shape. Ofcourse it bulges out, but that's okay, because there's loads of space (relatively speaking) underneath there. No problemo. I sort of rolled the wires together into a bundle to keep them together when putting the cover back on.


Omgomgomg a blue light, I didn't expect that. :-P Also, you can see the beveled edges around the fingerprintreader. It's slightly embedded, slightly deeper than the surface of the eee PC, but as it is, it works fantastically. Just swipe, and voila, it works. I was quite happy when, after disassembling/reassembling the eee PC 5 times, it finally worked.


And it does look rather sleek, even if I do say so myself.


My cat especially thinks it looks fantastic. She's so fascinated by it (as you can tell from the picture), and also annoyed that I didn't play much with her today. Perhaps it's time again to pay more attention to her.


If you have any questions, please don't hesitate to ask.
If you want to give me lots of money, please hesitate even less.

Last edited by novaflash (2008-06-30 10:39:10 am)