LCD + Digitizer hack

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LCD + Digitizer hack

Postby theblobinc » March 11th, 2014, 6:43 pm

OK,

for my project I have salvaged a 12.1" touch screen from an Hp tx2 ultrabook or w/e you call them.

either way I now have the lvds controller stuff figured out and ordered online, but am left trying too not only figure out the pinouts on the digitizer, but also a simple way too interface a normal pc with it.

the digitizer is a N-Trig duo sense capacitive touch screen, that as far as I can tell requires a regulated 3.3v power input(over 3 pins), usb, and a ground.

with-in the screen assembly there is present a "DATT3TH18B0" board with an input(9 pins) that comes from the laptops motherboard and 2 outputs.
one of which leads to the webcam(5 pins), and the other too the ffc ribbon on the capacitive touch screen(10 pins).

I've been trying too find some pin-out information for the datt3th18b0 interface board, but since its an HP product I doubt I will find much.
(it should be mentioned that the datt3th18b0 does have what looks like a SMD 3.3v voltage regulator(5 contacts 30lf) along with 2 resistors and 2 capacitors)

~~~~~

so thats where im stuck? most of the needed parts are already there, its just a matter of figuring out pin-outs without screwing anything up.

at first I want this screen and digitizer too interface with my computer via usb and hdmi, so it can in turn be a sweet ass wired keyboard, but later i'm planning too try make it into an HPC or some sort.(1 problem at a time)

anyways its an interesting project, but I need a little bit of help :)
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Re: LCD + Digitizer hack

Postby Retroplayer » March 12th, 2014, 1:28 am

Well, the first thing to look for... on the HP Ultrabook does the camera and touchscreen show up as USB devices? You can determine that by going into the device manager and looking at the resources. I would imagine that it is using a standard interface that would work for both the camera and the touchscreen, so my guess is either USB or I2C. Knowing that will narrow down your pinout reverse engineering.

If it is USB for example, it will be connected internally to your motherboard hub. There may be extra signals for powering, resetting, etc... but the bulk of the interface will be through USB. USB devices usually have 1.5K resistors pulling up the D+ line and pulling down the D- line. So look for traces that go to pull-up/pull down resistors (or measure the lines between VCC and GND to find them.)

Finding VCC and ground is easy. Just look for the biggest electrolytic cap on the board and the positive side will usually be your VCC and the negative side your ground.
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Re: LCD + Digitizer hack

Postby theblobinc » March 12th, 2014, 10:15 am

unfortunately there are no traces visible on the interface board.(the type of PCB used integrates them within an internal layer)

my best guess so far is if the interface board has 9 pins 8 of them will be 2 usb, and the remaining one will be a ground.

but thats just a guess, I do know for sure that the cam uses usb, and the touch screen as well uses usb.
(the specs I found online for the touch screen denote usb/spi)
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Re: LCD + Digitizer hack

Postby st2000 » March 16th, 2014, 9:25 am

I am going to guess that these interfaces have not been abstracted to the point that they are some type of USB interface. The PC market is fierce and adding that level of sophistication is not necessary. I believe it is much more likely that the touch screen interface is some type of I2C. (The camera might be as well.) As such, I would inspect the circuitry the touch screen is connected to and start searching on the chip numbers in order to find the function of each pin.

Just as an example (repeat: Just as an example), here is the specifications for another LCD w/integrated touch screen:
http://www.newhavendisplay.com/specs/NH ... XI-CTP.pdf
You will find the touch screen interface to be of type I2C.

Last point, (again guessing) the touch screen may be manufactured completely separate from the LCD. That is, the LCD stickers may have nothing to do w/the touch screen.
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Re: LCD + Digitizer hack

Postby jongscx » August 25th, 2015, 10:32 am

I too have an N-trig interface board, but it has a 10-pin connector. Mine has labels that seem to indicate JTAG, but on the other side you can see "USB".

cropped.png
NTrig Interface


I bought a 15.6" replacement laptop LCD and have been trying to decode the USB interface as well. Hope we can help each other out on this.
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Re: LCD + Digitizer hack

Postby st2000 » August 25th, 2015, 9:31 pm

Lots of guessing. More than I like. But the way I see it, 9 of the 10 pins are defined by the silk screen. 3V3, N(negative), P(positive) & GND kind-of look like a USB port. Although USB ports are supposed to all be 5V. The other pins kind-of look like SPI to me. But you may be right about it being JTAG. To the O.P., what do you see w.r.t. USB devices on a working laptop? Do you see an N-trig USB device. All USB devices have vendor and device IDs. It shouldn't be much trouble to look these IDs up for an N-trig USB device. There's lots of help on the web getting N-trig USB touch screens running on a Linux box.
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Re: LCD + Digitizer hack

Postby masterbeta » June 13th, 2017, 2:47 pm

Just checking in to see if there was any further development on this.
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