Using an old laptop LCD for prop a display

kwinn

I have an LCD display from a defunct laptop that I would like to use as a display for my protoboard. The LCD is an LG LP121S2. Does anyone have a hardware manual or other technical information on this display? I have searched the LG site but there is no info there, and I have googled it but all the results are companies wanting to sell me one.
Also, I propose using this thread to gather information for recycling displays from laptops and other equipment for reuse.

Oldbitcollector (Jeff)

This topic resurfaces from time to time. I hate to burst the bubble because I would also
love to see this happen, but you are facing two problems. First, the variety of LCD screens
and the lack of documentation. Second, talking to an LCD that size would require a good
deal more memory and I/O than you have. Most of these LCD's have a VGA-to-LCD conversion
process. (A couple of chips on the motherboard) If you could somehow connect the VGA
RGB to this chip (again documentation is a hassle here) you *might* be able to pull this off.
However it would be extremely tough for anyone to duplicate your exact situation, although
we would sit and be amazed by your pictures. [noparse]:)[/noparse]

You are really better off going with an existing VGA flatscreen (either from a monitor, or
purchased from a vendor that specializes in this item and can provide documentation) than
trying to recycle it from a laptop.

With all that said, know the challenges and try it anyway. We could really use a breakthrough here. [noparse]:)[/noparse]

OBC

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
New to the Propeller?

Check out: Protoboard Introduction , Propeller Cookbook 1.4 & Software Index
Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
Got an SD card connected? - PropDOS

hinv

I was thinking about this. Isn't there memory behind these pixels in the display itself anyway?
I guess what would be needed would be a way to get at that memory via a random access interface rather than a sequential scan.

Ale

Datasheet4u has the following pdf:

www.datasheet4u.com/download.php?id=559975

That includes only a pinout.

As Oldbit collector pointed out these screens need a lot of memory, but.. this particular has the advantage of needing RGB (6:6:6) syncs, clock and some enable signal. You need a clock so the video hardware of the propeller may not be suited. OTOH if you can coupe with low resolution... or even few colors, you can do yourself a simple driver. The syncs should be more or less standard depending on the resolution. If it is 1024x768, the propeller can generate 512x384 using 24kbytes of memory. With limited color support. It is always a matter of compromises.
This panel seems to lack any memory besides a shift register :-(

Edit: Sorry it is a 800x600 pixels panel, then using 400x300 is still adequate.

Have fun.

Post Edited (Ale) : 1/30/2009 5:04:22 PM GMT

kwinn

OBC, hinv, Ale, Thanks for the quick reply. I found the pin outs at datasheet4u and took a look at the display. It does look like it only needed a clock and enable (or whatever DTMG is) in addition to the regular VGA signals to display an image. As luck would have it the laptop my neighbor asked me to take a look at uses the same LCD panel so I decided to verify that my panel works and scope the signals. Sadly, my panel does not work.

ErNa

To reanimate old hardware is always a fascinating task, for you get something without having to spend money. You have to spend time and you get knowledge. Added value without VAT. So a question pops up in my OCPU: VGA-Adaptors have known interface (hardware/software), incorporate memory and generate vga-output. It should be rather simple to connect them to a propeller. Did anyone ever try it?
ErNa

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
cmapspublic3.ihmc.us:80/servlet/SBReadResourceServlet?rid=1181572927203_421963583_5511&partName=htmltext

Post Edited (ErNa) : 1/31/2009 12:55:46 PM GMT

J. A. Streich

ErNa and kwinn,

VGA drivers for prop exist, VGA adpators are availible for the protoboard in the accessory pack. Old CRT VGA monitors are a dime a dozen as people move to LCDs, and smaller LCDs (though not the super small ones which cost quite a bit) as people trade up. There are several drivers and demo programs for VGA, It's probably better use of time these for your project, if space allows and it doesn't need to be portable. For cheap composite screens there are some low cost mini-dvd players that have been used on a few past projects we've seen in this forum. I've gotten one of the model in question, I can post info on it a little later.

kwinn

ErNa and J. A. Streich,
I am using a 15" LCD monitor currently and the VGA drivers work well at all three usual resolutions. The problem is that my work space is still a bit crowded and I was hoping to resurrect one of the smaller left over LCD,s from defunct equipment to reclaim some workbench space. The ideal LCD would be a ~10" unit that supports VGA at 640x480, with the second choice being a 12" one. Being able to reuse a retired piece of equipment is a great feeling (made even better if it costs $0.00) so I would have been willing to spend some time, effort, and a little money to make it work if it was possible. I was even contemplating using a prop with some external ram as the interface circuit to make it as flexible as possible (standard VGA, serial text terminal, serial graphics terminal).
I am hoping that the rush to hi def (1920x1080) will make that the standard highest resolution, and that screens in submultiples (960x540, 480x270, etc) will also become readily available and inexpensive. Of course world peace, a fair and just society, and a stable prosperous economy would be nice too.

ErNa

My "flash" was certainly a bit off-topic. An LCD-Screen with VGA-Input always comprises a controller with memory and a vast amount of pins. The propellers advantage is to simple generate VGA-Signals. A LCD-Screen from a notebook can't be driven by a propeller for lack of pins, speed and memory. My intension just was: spot the fact, that anyone can have old ISA-VGA pc-cards and connect the isa bus to a propeller. That would give 256 kB of memory (rather slow communication) and the ability to generate VGA-Signal. But it needs a driver. ErNa

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
cmapspublic3.ihmc.us:80/servlet/SBReadResourceServlet?rid=1181572927203_421963583_5511&partName=htmltext

kwinn

ErNa,
I did not find your post off topic, and I am not so sure that it would be that hard for the prop to drive this particular LCD. There appear to be row and column drivers mounted across the top and down one side of the screen. I have attached the data sheet with the pinouts and it looks like all it needs is 6 bits each for red, green, blue, horizontal and vertical sync, a clock signal, DTMG (whatever that is), and power for a total of 22 (or fewer with a bit of added hardware) signal pins. Judging by what I see on this forum I think a lot of the LCD screens could be interfaced without too much of a problem. The biggest obstacle is lack of information, not expertise and creativity.

I have interfaced an old 8 bit ISA card to a micro (not the prop) and it is not that difficult for the hardware. It is a bit more difficult from the driver perspective, but doable if you can get info on programming the video chip. The main problem is the number of different video chips used and the lack of information on them.

ErNa

Ok, I thought that the LCD-signals will be quite different from the vga-signals. But I found www.datasheetarchive.com/pdf-datasheets/Datasheets-pdf-14/286727.html, a different display, but obviously there are TTL-inputs and not LVDS, so it could work. ErNa

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
cmapspublic3.ihmc.us:80/servlet/SBReadResourceServlet?rid=1181572927203_421963583_5511&partName=htmltext

Ale

Well, ErNa got it right. That datasheet explains what DTMG is, some data enable signal. If we could only get those 10" displays cheap... (Pollin sell some but are mono :-(, they had a DSTN 800x600 some weeks ago but they are gone now). A pity the lamps need 2.6 Watts.

Cole Logan

I have a 12.1" LCD screen that I got from a point of sale terminal for $25. It also came with the backlight inverter, a power supply and a touch screen.

kwinn

Cole, it looks like you and I had the same idea. I took a look at your data sheet and it looks like you have the earlier version of the LCD as well. Even the pinouts appear to be the same. I found that my display was not working by plugging it into a laptop that uses the same display so I put this project aside for now, but it looks like the only additional signals needed to make the display work is the DTMG and clock signal. The DTMG looks like it could be done by the prop along with the VGA signals, and I wonder if the clock could be generated by the counters/PLL circuits or derived from the crystal. If I come across a working LCD in the future I will be doing some experimenting.

FYI I have attached the data sheet.

Cole Logan

Well I know that my screen works and wendesday I'm going to order the connector that I need to make it work. And from what I have found A lot of screens use this same timing protocol. It looks like this sony 4.3" screen is the same. www.sparkfun.com/commerce/product_info.php?products_id=8335

kwinn

Makes sense, they all work on the same principle so I guess the only difference is how many row/column drivers they need. Please let us know how it works out.