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Author Topic: Salvaging touchscreen from a Toshiba Portege M780  (Read 1355 times)
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« on: August 03, 2017, 10:09:09 AM »

So, this has been on my mind forever (well, since getting the laptop anyway.)
If I knew of this forum, I would have done it sooner.

So the idea is just to use the screen as a second (*cough* third *cough*) monitor for my desktop.
The laptop itself is perfectly fine, but under powered for the software I'd like to use (photoshop, paint tool sai, streaming software).
I'd like to have the function, but have my desktop handle the grunt of the work.
I'd still like to use the laptop as well, I just don't need the touchscreen function on it.

Anyway. To the actual question.
What difficulties should I expect when starting this project?
What hardware might I need to buy? Is there specific hardware for the digitizer?
I've read this post which mentions Portege, but not the M780 specifically. Is the hardware comparable?
Will I need to code anything? If so, what? Or is it all handled by the hardware?
What's a comparable screen for the laptop?

I'm sorry, I know these questions have probably been answered before.
It's always daunting about starting anything where I don't know where to begin.

Any help will be appreciated. Thank you for making this forum exist!
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« Reply #1 on: August 05, 2017, 11:12:30 PM »


As I found after very short research, base models of M700, M750 and M780 have the same or very similar screens - LCD + Wacom EMR digitizer + resistive single-touch. Probably M700 have CCFL backlight while M780 have LED backlight.
I talk about base models, 1280 x 800 px. M750 have hi-res screens as option, 1400 x 1050 px. If that screen have LED backlight, You should look for it. As I figured 1280 x 800px have very limited compatibility - some video cards autodetect this resolution, most not but I can force specific resolution, few doesn't accept and cannot force specific resolution. That's sad.

Back to topic. LCD (glass + drivers), LCD backlight, EMR digitizer and touch digitizer are separate devices. You need special adapter for each.
1. This TabletPC is relatively old. I assume that LCD gave LVDS interface. You need to use VGA->LVDS or HDMI->LVDS converter to connect LCD to PC. I mean active converter + special cable between converter and LCD. You can buy universal converter with wide range of supported resolution (select via jumpers or upload via USB stick) or specialized converter (programmed by seller). You cannot make connector for LCD panel. You can easily buy special cable (price may vary depend on type of connector) or buy LCD with cable, cut motherboard connector and make DIY wiring.
2. CCFL backlight have separated driver, always hidden near LCD module. You need to find pinout for that module and connect it. LED backlight have independent circuit located at the same circuit board as rest of LCD things. It use the same connector too, just have separate pins. Pinout are available at LCD datasheet. BTW, LCD is useless without datasheet or at least pinout.
3. There are tree types of EMR digitizers.
You can found one with USB interface - add 3V3 voltage regulator and proper USB connector, that's all.
You can also found one with RS232 interface - add RS232 to RS232-TTL and digitizer will be usable on Linux or WinXP, or add WasBee converter and digitizer will be available on Linux, modern win (probably Mac too).
Last type have unknown interface between EMR digitizer and touch digitizer but known interface between one of them and motherboard - usually USB but sometimes RS232. So don't worry. WaxBee doesn't cost fortune and playing with these things are worth.
4. Portege series use single touch resistive panel - can be used with any tool that aren't too sharp to scratch it. That panel are made of solid back plane, air gap and thin foil on top.
As You wrote, You don't need that part so You can safety disconnect panel from dedicated hardware, maybe remove some parts inside. Really no issues here.
But I have to say something about that touch panel itself. IMHO drawing over resistive touchscreen wasn't the best option. I recommend You to replace touch panel with layer of glass/plastic or chose different tablet to play with it. But that's my opinion based on regular resistive touch devices. Maybe that screen have special durable version, who knows.

Any errors in spelling, tact or fact are transmission errors.

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« Reply #2 on: August 08, 2017, 04:55:21 PM »

You won't have any trouble getting the digitizer to work with a teensy, but you need to make sure you have a datasheet for your particular screen. I have this LCD assembly from a Portege R400 and though the digitizer works great, finding a datasheet for that particular Toshiba screen has been a major pain in the ass.

 If you can find a datasheet for your screen you should be all set - just order a controller board and a Teensy and start thinking about how to build the housing. Often using the laptop's upper half as a housing and screwing a box with the controller on the back is a good solution.
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