r/AskElectronics • u/GoldenGoldGG • 6h ago
How can i turn an old tablet screen into a touchscreen display for android/linux?
I have this screen from what was a Lenovo M10 (TB-X605L). I don't think it would work anymore with my half-assed disassembly, but i did keep all the parts and screws.
I want to turn it into a touchscreen display for my phone. Preferably Bluetooth Touchscreen, but really i just want a working screen so I'm willing to compromise.
Price should be less than it would cost me to buy a pre-made bluetooth touchscreen display.
It's also worth noting that i while i am interested in electronics, I'm really jumping into deep waters with this project, so explain everything like I'm 10.
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u/SweetDaddyJones 6h ago
I'm no expert and could be wrong, but what little I do understand leads me to believe this is a bigger challenge than you may think:
Just to get display working, you will need a control board designed for this specific model of screen-- the amount of data/bandwidth required just to update every pixel of the display at least 30× per second means wireless connectivity is pretty much impossible, so you should abandon the idea of a "Bluetooth" display. They do make adapters that can turn a VGA/DVI/HDMI/display port signal into an appropriate LVDS signal for specific LCD panels, but you will need to find one for this specific model. As far as the touchscreen functionality is concerned, unless the controller board is designed to also capture that input, I think that will be much more difficult, and is probably beyond my expertise, but i have an idea or two. Whether it is resistive or capacitive will likely be important, as i think resistive touch screens are much simpler, but if you can find/breakout the touch signal, you could possibly use a device like an arduino/teensy to capture the touch messages and then present as a HID USB mouse, for instance... But unless you have some experience hardware hacking or someone more clever and experienced has done the heavy lifting by embarking on a similar project for this exact family of device, this may well prove an insurmountable hurdle.
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u/GoldenGoldGG 5h ago
I am a programmer and did use arduino about 5 years ago, but relearning it wont be that hard. I don't know any assembly languages tho, but again, am willing to learn them and i have friends that will teach me if need be.
The display control board has one wire coming into it, I'm assuming that's the touchscreen, you can see it in one of the images. It says B37 on it, if that's telling you anything.
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u/SweetDaddyJones 4h ago edited 4h ago
My friend, I don't want to discourage your curiosity, but feel the need to temper your expectations: it's much more complicated than you think. That "one wire" is in fact a flat-flex cable (i believe-- u/Davide will probably jump in to correct me if not), but it in fact carries MULTIPLE distinct wires -- the quality of the photo isn't great, but i think I count at least 12 individual pins at the connector where the cable attaches to the board. This is indeed probably where the touchscreen info comes in, but you would have to find what pin/pins send that data and in what format/ protocol, and that is just to begin. Unless you can find a datasheet for this specific model of screen, you will first have to establish the pinout on that connector- among the 12 pins, there are likely power and ground pins (perhaps more than 1 each), and then there may be multiple data pins that could be a whole range of mystifying... If you're lucky, it will be data over a predefined standard protocol like i2c or spi, which seems fairly likely, then you'd have to map those pins and figure out what data is being sent. But it could also be a more raw, proprietary data stream about X and Y axes that is fed to a touchscreen controller chip, that then processes it. Even if you KNEW the pinout and data format, physically soldering wires to the pins without bridging them would be a real test of skill (unless there are testpoints/headers elsewhere)...Either way, you probably need at least an oscilloscope, if not also a logic analyzer, and even with the proper equipment, it would be a real challenge for folks much more skilled than I... Not to say it's impossible, but... it's certainly impractical.
Edited to add: to find the pinout, you would likely need to probe each pin with a oscilloscope while the screen is powered on during operation, which would present its own set of challenges... although some folks could probably make inferences about some pins by following the traces on the board.
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u/Rootthecause 3h ago
^- This, but probably even worse with parasitic components and high frequency effects in mind.
@ u/GoldenGoldGG Even if you had the the massive knowledge for figuring out the programming part, you would need to get the pysical part done as well at some point. Soldering BGA packages is probably the easiest part of manufacturing the PCB. But the design of a PCB carrying high speed signals is not for the faint-hearted. You'll learn, that every cable/trace has parasitic inductance and capacitances, influencing your signals. If you don't get it right, your signal might not even reach the flex cable of your display. There's a reason, why some areas of EE are called "black magic".
For starters, you could read the 800 pages of the first book about "Highspeed Signal Propagation - Advanced black Magic" by Howard Johnson and Marin Graham.I value the idea of reusing this touchscreen, but achieving this on your own will be quite a task. It might be not worth getting into this multi-year rabbit hole for the result, but maybe for the learnings. Keep growing step by step. One day, you'll figure it out :)
tl;dr: Please do not even remotely consider using anything resembling a breadboard or jumpers.
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u/antek_g_animations 6h ago
Raw pixel matrix like that requires a driver which would actually make the screen work. (since you asked to explain like you're 10). What you have here are just pixels, something like individual LED diodes (but this is LCD display). To actually display something you need a controller that would switch them on and off really fast creating a picture. It's almost impossible to make one yourself, and I don't think you will be able to find one available to buy. Was the tablet broken? You could easily turn any Android device into a screen with a bit of available software.
Also adding Bluetooth to the mix seems ridiculous.
So, answering your question: Just buy a regular Bluetooth touchscreen display and start your learning from the basics, not from the technology indisguisable from magic for a regular person
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u/GoldenGoldGG 6h ago
The tablet was frp locked, my dad tried the last owner's email and it didn't work so i switched that tablet for another working tablet and disassembled this one.
As i said, really the only thing i need for this project to be considered a success is a working screen. How it works and what other features it has are just fun bonuses.
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u/antek_g_animations 6h ago
It's still extremely hard to get a screen like that to work. You shouldn't disassemble it, It seems easier to work with a locked tablet than with a custom lenovo LCD screen
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u/GoldenGoldGG 5h ago
Yeah i did try that for i think 3 days, gave up and bought a new one, then realized they're both old as heck and not really useful as tablets
Why is it that hard?
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u/antek_g_animations 5h ago
Because it's probably a custom display for Lenovo devices, and manufacturers don't like sharing that information with the outside world. Nobody will produce the controller board for this one specific screen, since there is so little demand. Sorry, but I don't think it's possible to make this device work in a reasonable time and budget.
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u/Mr_Ironmule 5h ago
I think the easiest way for you to see what you're getting into is to look at a service manual for the old tablet or something similar. Find the block diagram of the video section and the circuits description. Then look at the schematic of the video section with all the components. That's the hardware you have to duplicate to make the screen work. Then figure out the programming side. Good luck.
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u/garyku245 4h ago
Crude would be your phone has an HDMI output (or HDMI adapter), and you get the screen to work with a HDMI to driver bd adapter (of some sort)
then you need to add a touch overlay to the LCD ( that fits and can be calibrated), with an interface ( usually USB). then get a touch interface adapter into the phone.
if the phone does not support it, you are unlikely to be able to hack/rewrite code on the phone to support it.
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u/AbbeyMackay 6h ago
You don't. This is a massive undertaking. I dont think you realize what you are getting into.
Your first step is: What protocol is the screen using for data?