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Author Topic: Experimenting with the HP 2710p Tablet PC digitizer (SU-12W18A-01X)  (Read 58592 times)
Pesho
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« Reply #195 on: September 20, 2016, 07:16:20 PM »

What's the foil for? Though I suspect it's got something to do with the 'jitter' problem...

Foil is preinstalled from the factory on HP laptops. It's most likely there to shield the LCD and digitizer boards from the wifi antennas that sit near those places. It has nothing to do with jitter since the digitizer already has a foil backing as part of its construction.

looks like i am better off ordering a 12.1" kit instead, anyone know of a good US supplier, i can move the wacom pad and the safety screen over to the new kit...

Do you mean a controller kit or an LCD screen?
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dracomenda
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« Reply #196 on: September 20, 2016, 07:40:01 PM »

the foil is for grounding and shielding purposes, ill be replacing it with conductive foam instead
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dracomenda
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« Reply #197 on: September 20, 2016, 07:41:57 PM »

i'll have to order both, they fried my only hydis screen so its back to the drawing board at the moment, need to setup the teensy though and get the wacom pad ready for the new screen when i find one
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Pesho
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« Reply #198 on: September 20, 2016, 08:55:39 PM »

i'll have to order both, they fried my only hydis screen so its back to the drawing board at the moment, need to setup the teensy though and get the wacom pad ready for the new screen when i find one


Since you're looking for a screen, check out "discountedlaptopparts" on ebay - http://www.ebay.com/itm/HP-EliteBook-2730p-LCD-Touch-Screen-with-Digitizer-Matte-12-1-HX121WX1-/380865241056

They have great deals on this stuff with free US shipping, it's where i got mine from. The link above is to an HX121WX1 from an HP 2730p. Like i mentioned earlier, that model is transflective and more readable outdoors.
« Last Edit: September 20, 2016, 09:02:24 PM by Pesho » Logged
ThrowingChicken
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« Reply #199 on: September 27, 2016, 02:04:49 AM »

What was your issue with the controller? I've been able to drive mine just fine... About it getting hot - that sounds like an LVDS cable inserted backwards or the wrong way. The way they attach to the controller board is tricky - nothing is marked, and there are more pins than on the connector. Also the connector on the LCD's side can be inserted both ways making it even easier to mess up. Can you post pics of the connectors and setup?

Keep in mind, it has been 3 years since I messed with any of this stuff. If you go back to this post here you can find in this thread where I start discussing the issues I was having.  Looking back at it again, the backlight would come on, but I'd get mostly a black image, occasionally with some colored lines.  Also, this is the 2710p tablet, not the 2730p that you linked to, with different model numbers for the screens and digitizers, so they may not be the exact same. 
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Ertew
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« Reply #200 on: September 27, 2016, 10:11:49 PM »

Can you post pictures? LED backlights don't need high voltage, it's CCFLs that need high-voltage AC (via inverter) to work. If they supplied a second board that would likely be a DC-DC converter.
You're wrong.
CCFL need inverter - constant current driver (about 5-10mA) with high voltage (100-1000V during work, more at startup). Usually we named it inverter because output are AC. But CCFL will work on DC too.
LED need driver - constant current DC driver (from 20mA up to 1A) with usually 18-100V voltage generated via step-up DC/DC circuit.

Larger panels have separate LVDS and backlight (raw LEDs) and need separate backlight driver.
Smaller panels usually integrates driver at same board as rest of LCD logic. But driver still exist and You can easily found cable between LEDs and driver section.

The "traditional" 6-pin backlight connector on universal drivers are just control (on/off and sometimes PWM) output and power supply output for typical backlight driver, no matter type of driver.

BTW, You can buy expensive HDMI/LVDS converter with build-in constant current LED driver like this unit:
https://www.aliexpress.com/item/HDMI-VGA-AV-Remote-LCD-Controller-for-15-6-LP156WH4-TL-A1-LED-Screen-1366x768-Free/32599731171.html
Notice connector on top-left of the board, the same as CCFL connector. Only typical CCFL transformer is missing, so it must be output for LEDs.




I have no idea how you would use a LED panel with a 'universal' controller, but I have seen eBay sellers selling specific controller boards for some LED LCDs. Don't know if they work, though.

The LED-related wires come out of the same connector on the LCD's side, they're just separated out to a different connector on the board's side and plug in where the inverter normally goes. Way more compact. Newer controller boards are designed with that in mind so that you can use them with both CCFL and LED panels. Got mine off Aliexpress, not sure if they're on eBay.

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Can You check power consumption for this converter? I mean input current and voltage for bare board (LCD disconnected) when converter fully working. If no, please at least check temperature of main chip after few minutes of work.
I'm searching for energy-efficient and cool LVDS converter (VGA or HDMI input) for my mobile rPi project. Converters based on TSUMV59 are great but need to much power and generate too much heat. Even HDMI->VGA->LVDS works cooler than this.
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Pesho
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« Reply #201 on: September 28, 2016, 08:27:53 PM »

You're wrong.
CCFL need inverter - constant current driver (about 5-10mA) with high voltage (100-1000V during work, more at startup). Usually we named it inverter because output are AC. But CCFL will work on DC too.
LED need driver - constant current DC driver (from 20mA up to 1A) with usually 18-100V voltage generated via step-up DC/DC circuit.

Come on, there's nothing wrong with what i said. Using CCFL's with DC is impractical and almost never used. You won't find LCD panels with a DC-operated CCFL backlight.

Quote
Can You check power consumption for this converter? I mean input current and voltage for bare board (LCD disconnected) when converter fully working. If no, please at least check temperature of main chip after few minutes of work.
I'm searching for energy-efficient and cool LVDS converter (VGA or HDMI input) for my mobile rPi project. Converters based on TSUMV59 are great but need to much power and generate too much heat. Even HDMI->VGA->LVDS works cooler than this.

It gets very hot at the voltage regulator, so i wouldn't recommend that particular one. They run off 12V too, which would be a headache since you'll need to regulate it down to 5V for the rPi. I remember a store selling driver boards that were designed to be used specifically with a raspberry pi, but were meant for 7'' displays. Ridiculously expensive too. In my personal opinion, an rPi is a pretty poor computer, there are cheap second-hand tablet and laptop motherboards that are much more suitable as mobile devices, with a charge controller and LVDS driver in the one thin-profile board. The 2730p i got off eBay for 20$ has comparable dimensions and weight to a raspberry pi hack-top, except with a faster everything.
« Last Edit: September 28, 2016, 08:31:26 PM by Pesho » Logged
ThrowingChicken
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« Reply #202 on: October 06, 2016, 11:39:01 PM »

i'll have to order both, they fried my only hydis screen so its back to the drawing board at the moment, need to setup the teensy though and get the wacom pad ready for the new screen when i find one


Since you're looking for a screen, check out "discountedlaptopparts" on ebay - http://www.ebay.com/itm/HP-EliteBook-2730p-LCD-Touch-Screen-with-Digitizer-Matte-12-1-HX121WX1-/380865241056

They have great deals on this stuff with free US shipping, it's where i got mine from. The link above is to an HX121WX1 from an HP 2730p. Like i mentioned earlier, that model is transflective and more readable outdoors.

I went ahead and picked one of these up.  Which LCD controller are you using?  Is the pin out for the Teensy the same as it was for the 2710p digitizer? 
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Aerendraca
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« Reply #203 on: November 02, 2016, 02:30:08 PM »

I see you're worried about power consumption and heat from the LVDS controller. My suggestion would be to get some cheap switching dc step down modules (such as LM2596) and remove or bypass the linear regulators.

The LM2596 (variable module) is good for stepping down voltages from up to 40V to between 37V and 1.2V and can handle 3A of current. You can also get fixed output versions in values 3.3V, 5V, and 12V.

As a quick note: I would suggest though that some heat would definitely be generated if you stepped down 40V to 1.2V.


* LM2596Reg.jpg (27.35 KB. 400x400 - viewed 54 times.)


They don't get hot and they're much more efficient than a linear reg. Only problem here is that you trade of efficiency and thermal benefit with space.

« Last Edit: November 02, 2016, 02:36:25 PM by Aerendraca » Logged
Pesho
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« Reply #204 on: November 02, 2016, 04:02:55 PM »

Quote from: ThrowingChicken
I went ahead and picked one of these up.  Which LCD controller are you using?  Is the pin out for the Teensy the same as it was for the 2710p digitizer? 

I replied to your email about this, but i'm going to post the info here too for anyone interested:

I'm using this controller here: https://www.aliexpress.com/item/HDMI-LVDS-Controller-Board-40-Pins-Lvds-Cable-Kit-for-Raspberry-PI-3-LP156WH2-TLA1-TLE1/32645792288.html

I told them to program it for an HX121WX1, should work equally well on the non-transflective HV121's too.
- Be warned that it does get kinda hot.
- You will have to send them a message with the datasheet and ask them include the correct cable for your panel, which is an extra 7$. They will ask you to add the controller to your shopping cart etc. without paying. It's so that they can readjust the price first before you pay.

For the Teensy - Yes, pinout is the same across all the serial digitizers with a 14-pin connector, at least the ones i have here. It's:

 
9 - RX (D2 on the Teensy)
10 - TX (D3 on the Teensy)
13 - VCC
14 - GND

I think you can use Pin 1 as ground also, check on your connector. I've tested this setup on at least two 2730p digitizers (SU-12W18A-04X), one from a Toshiba Portege R400 (SU-12W07E-01X) and some 4:3 ones from an HP TC4400 (SU-025-C02) - all of them work.

My suggestion would be to get some cheap switching dc step down modules (such as LM2596) and remove or bypass the linear regulators.

Not a bad idea, but doing that is not as easy since the board is entirely SMD components. Even just a beefier regulator should do the job, but putting it on there might pose a challenge.
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Aerendraca
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« Reply #205 on: November 02, 2016, 04:18:32 PM »

True it would be a bit fiddly, but it's do-able.

Interesting board by the way, I've not seen that one kicking around before.
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