LCD panels

[Tinker]

Originally posted by uvodee
Well DVI out can be foudn on some later Radeon and ATI video cards...
is that what you think could do the trick?

ATI radeon 7500 (bought bro. one so I know) $75.00
ATI radeon 8500LE $95.00
ATI radeon 9700 $399.00 (newest radeon)

All can be bought at www.newegg.com CC/Cashies check/MO payment accepted....somebody have a ati radeon? All the models I listed have dvi/multi mon. suport. So you can see what is on mon. and projector at same time. Can be in two dif rooms this way! For those who dont know DVI is the lcd mon hookup on these cards which is pure digital. Reg. crt mon.s are analouge.

[Tinker]

Originally posted by moses
No, there is no way to hook up a controllerless LCD with a DVI port. Not without a lot of electronics. As for pinouts, I can probably get them for you, but they won't do you anygood. You will have probably 4 or 8 data bits, a frame start, a data latch pulse, and a data shift pulse. Plus your grounds, driving voltage, and occasionsally a LCD off pin. There is no way just to hook it up to a parallel, seriel, or ISA expansion slot, as it requires too much bandwidth. Specifically it requires the horizontal resolution times the verticale resolution time the color depth. Just for an example 320x200x8, QVGA. Most of your LCD's require that this data be transmitted 60 times a second. So you have, just for that little baby screen, 30Mb/s. There isn't a way of taking a "digital" signal to drive the LCD directly off of most video cards, as most video chipsets don't provide the nessacary(sp) lines to drive a LCD. If you have a older Chips and Technogoly video card, you might be able to drive a LCD off of it. However your LCD configuration data is generally stored with the video BIOS, and you would have to find a way to hack the BIOS to the point where it would work with your specific LCD.

DiVX( or rather DiVX ;-)) is a high compression lossy video codec based off of MPEG4. It isn't made to copy DVDs, it just often is used in copies because of it's extremely efficient copies. It can very easily exceed VCD quality(which is a terrible MPEG1 compression). DVI is a digital video interface, that can provide both analog and digital video, depending on which DVI interface you have. It doesn't generate LCD timing signals.

Makes sense! I mean there is still nothing telling the panels Liquid crystals to twist/untwist bending light thorugh polarizers. Without this no pic. Also the lcd mon.'s have controler boards so they have to have them. Nice catch there moses!

[remp]

Moses

Good stuff about the compression etc but in the

Google search lcd transmitter receiver

I can across several sites describing new transmit receive single chips that provide all the timing needed and can run fast enough to not need any compression at all.

Surely the digital interface starting to appear on some video cards is exactly designed for driving lcd or what is it there for.

My read of the situation is this.
Inside your computer its all mostly digital. Then the output to a monitor is changed to analogue. That D to A process causes some degradation of the video. Whether it be a CRT monitor or and LCD monitor it only accepts analogue.

That is because the huge amount of digital data cannot be sent over a 10 foot video connecting cable. I think thats the reason also for compatibility with existing monitor technology

But things are changing. The newer video cards have a special output socket so if you plug in a standard analogue monitor you get analogue but if you plug in a digital only lcd connector into the same output socket you get digital data.

This technology was mooted several years ago but stalled for various reasons. Possibly the difficulties in transmitting such high amounts of data over the monitor cable. Also CRT monitors are still readily available and cheap and good so there is no good reason to change to a more expensive LCD monitor unless you need the real estate on your desk or you want the "supposedly" better monitor performance with a good LCD and a digital connection.

No one is going to buy crap so the digital performance will have to offer good solid advantages or users will stay with what they can buy off the shelf today namely analogue monitors.

So my thinking is if the digital output on a video card is there, it must be there for a good reason and if its purpose is to drive a LCD panel how can we take advantage of that to drive LCD panels that have no driver board. But may need a receiver board of some sort.

This link from National semiconductors has a good explaination and its dated 1996.
www.national.com/news/1996/9611/dm96006ldr.html

This link explains something about dvi
www.datapro.net/dvi.html

Maybe I am on the wrong track

[uvodee]

one guy in my local comtputerstore Infotech , manned for 90 pct with funny Korean guys, asked me if i could leave the NEC lcd screen so he could figure it out 'after hours' .
he would not charge me for anything except when he comes up with the hardware ofcourse. however i told him that $200 would be too much!
i will check tomorrow evening and see if they found the way to connect the NEC via a Radeon or ATI.
if not so be it , i can still get a set at earthlcd.

[remp]

Continueing my laymans investigation into laptop lcd panels and can we use them, I have found out some things.

If you damage your laptop LCD screen you or your computer technician locates an exact replacement, removes the old lcd fits the new lcd and connects the high speed link to join the video to the lcd.

The point about this is the replacement is simple. All the electronics that need to be on the replacement lcd are already fitted.

I think this is correct. I do not know for sure because I have not replaced a laptop screen but various information on the net indicate it is true.

If this is correct then several possibilities to use laptop lcd's become a little closer.

(1) Every internet article about laptop lcd's say the row and column drivers are fitted during manufacture
(2) All laptops use a high speed transmitter/receiver combination to transfer digital information to the laptop LCD.
(3) I think the receiver is also fitted during manufacture but not 100 percent sure about that.

The laptop lcd now contains a lot of parts

At the laptop end there is always a high speed transmitter driven by the main video processor section.

One could say that all that is needed is the transmitter portion and a cable to have a working LCD but its not that easy.

There has been in the past non standard specification for laptop connection to laptop lcd so the FPD (flat panel transmitter/receiver combination may be a proprietry type specified by the laptop manufacturer.

That does not help us much

In 1999 a group of computer manufactureres got together and established a standard for driving digital LCD panels.

This is the DVI standard.

It is not mandatory but the idea is to get all manufacturers to use it so any computer can drive any digital LCD panel. And also presently available analogue LCD monitors and regular analogue CRT and also the new digital CRT's.
Different cables are used. The whole idea is to standardise the connector on the computer, to standardise the high speed link and most important for us to standardise the LCD receiver specs.

Also needed is the bios values determining important settings to drive a particular panel but the latest idea is the LCD panel stores all that information itself and it tells the computer video board how to send the information. This is to allow hot swapping of LCD monitors so hopefully bios is not involved.

So all this means if you can get your hands on a late model LCD panel it should have a DVI compliant receiver and you should be able to drive it directly from your DVI computer port.

No driver board required.

That is a simplified scenario. In real life it is very unlikely to be like that because even late model laptop LCD may claim compliance with DVI but for economy some essential parts may be missing. Secondly even if the laptop LCD is exactly compliant and it does work when connected to a DVI computer port there is no guaranteeing the PC board that contains the FPD receiver and "other stuff" can be moved out of the way to allow projection.

The essential part of this investigation is to show that a laptop LCD probably has a receiver already built in and could be made to work if "somebody" could supply a stand alone FPD transmitter. Perhaps one that is driven by a DVI computer output. This might be OK for the hot swap LCDs but of course in a laptop hot swappping is not used so we are stuck with the same old problem of driving a cheap laptop LCD without connecting directly to the motherboard. Several manufacturers do supply IC's and built up transmitter/receiver combinations. Panel link is one. Silicon image also.

It is interesting to note these LCD transmitter receiver IC's are dirt cheap. $8 -$10 dollars in quantities of a thousand but free samples are usually available.

I have to confirm if all cheap surplus laptop LCD's have a receiver built in and what standards were/are used.

Acknowledement.
The attached drawing was copied from Silicon Image website.

[Tinker]

Good stuff there remp! Very interesting especially the part about it having its own row column drivers! Thats very important. This mean it is of the "chip on glass" tech I have mentioned a couple of times. The driver chip should be on the glass substrate. Wether it would interfere with our projection purposes I dont know...keep looking thats some great info so far!

[remp]

Tinker.

Thax for that. Row and column drivers seem to be always along one side and top or bottom edge and not in the way for projection. Its the rest of the electronics that could be in the way. Anyone got a surplus laptop LCD to pull apart and have a look ??

Further delving with

Google fpd transmitter receiver

and

Google fpd asic

Several articles show that prior to 1991 everyone used their own means of connecting a laptop to the LCD panel and at that time they used ECL ( emitter coupled logic ) which can run up to 1000 mhz. That speed was ok for low resolution graphics such as cga ega and hercules with not much colour.

Then came VGA panels. ECL was right on the borderline of transfering data so National semiconductors developed a new system similar to ECL but using small voltage swings about 0.3 volts and differential operation. Differential operation allowed the same current that went to the panel to come back to the computer on the negative leg and they could run the thing with twisted pairs instead of expensive co-axial wires. This was highly important since all wires to the LCD have to go through the laptop hinge. The fewer expensive wires the better.

They claimed the low voltage swings and the differential operation allowed data transfer that created next to no radiated noise, and could be used up to XGA resolution at 24 bit colour.

The National system was adopted by most other manufacturers and is still the most common by far method of connecting a laptop to a laptop LCD screen. With continual improvements it can now drive any resolution and size laptop LCD

National today according to dollar business surveys have 81 percent of laptop to LCD business so the message for us is if you buy a surplus laptop LCD chances are very high it will be designed for the National semiconductors standard.

Unfortunately the National semiconductor system is slightly different from the new DVI standard. Would'nt you know it, but there is probably a lot of politics involved.

Anyway National semiconductor equiped laptop LCD's look promising and hopefully can be identified by the chip numbers.

Am trying to find out what more is on a panel apart from the row column drivers.
You would think a surplus laptop LCD would have all the IC's already fitted so it could be plugged straight into a Laptop. Of the correct model.

If thats the case all we are looking for is a National FPD (flat panel display) transmitter and a convertor that allows the National transmitter to be plugged into a DVI port.

I am also seeing that many Video cards have digital socket or pc connection points already on the board. That could be very handy.
Also a bare PCI card can get access to the video digital lines inside a PC. Its not that simple but the possibility is there.

[chbright]

you all may want to look at this site

http://www.geocities.com/p9019/lcdpanel

[moses]

Graphical LCD panels will almost always have the row/column drivers on the edge, or SoG(silicon on glass) on very modern panels, other wise they would block light from the backlight. ECL logic is a very very old implementation for digital logic. All modern LCD controllers are just CMOS. I've managed to display a image on a philips QVGA mono screen via a XPLA3 CPLD, just a static image and some VHDL. Generally all LCDs have the same set of inputs: Data(1-16 bits, generally), a frame start, data shift, and data latch. If you have a passive split panel(which would be worthless for video, most likely) you would have to seperate panels more or less, requiring two seperate controllers. Your DVI-D connectors are just a high speed serial bus, they won't drive a LCD with out a chip to interface to the row/column drivers. If you wanna drive a LCD panel, just buy a controller. If you're feeling insane, then try the VGA controller off of opencores.org or find a old CHiPs and Technogoly PCI/ISA card as all of the 65xxx chips could drive LCDs, including TFTs. Afterword you would need to hack the video BIOS by finding one intended for a LCD panel, then changing the controller interface data within the video BIOS.

[remp]

The question I was most interested in an answer was

Is the high speed link receiver built into a laptop LCD. ?

People who would know that are people who supply replacement laptop LCD's

Here is a link to a replacement company
www.buylcds.com/REPLACEM.HTM

And here is their text I was very interested to see.

**************

Replacing the screen
Before attempting any replacement carefully compare the new screen with the screen you removed from your Laptop. Perform a close scrutiny to be sure the new screen is a clone of the old one, or the vendor has assured you that the new screen is a proper substitute for the old.

Connect the data connector, then the backlight connector and position the display in the top cover, retaining it loosely with a couple of screws.

Reconnect the power, replace the battery and turn on the computer. If everything has been done correctly, you should now have a visible display.
If the display is satisfactory, power down, remove the cord and the battery, and reverse the above procedure, making sure to replace and properly tighten all screws.

***************

There is no mention about taking parts off the original LCD. Just plug in the data connector and backlight connector.

So it seems laptop lcd's designed to replace faulty ones have the receiver built in and also the row and column drivers and the timing electronics.

But what about laptop LCD's from surplus outlets. They may not have all the electronics fitted.