Putting laptop LCDs to use with an FPGA

We’re always impressed with the number of laptop displays we’re able to pick out of the trash. Most of the time the computer is borked beyond repair so we end up with a lot of functional but unusable LCD panels. As a service to us all, [EiNSTeiN_] figured out how to control an LCD panel using a cheap homebrew FPGA board.

LCD panels don’t use a simple protocol like VGA for turning pixels on and off. Instead, the very high-speed LVDS is used. LVDS is beyond the capabilities of simple microprocessors, so [EiNSTeiN_] built himself a clone of an XuLA FPGA prototyping board and set to work. After figuring out the signal lines to the panel, [EiNSTeiN_] pored over the timing diagrams for the LVDS controller and the LCD panel. From the data sheets, he figured out data is usually sent to the panel at about 500 MHz. The homebrew FPGA board couldn’t manage that speed so [EiNSTeiN_] cut the FPGA clock in half.

While LCD’s 60 fps refresh rate was reduced to 30 fps, [EiNSTeiN_] says there’s only a little flicker. Not bad for something that could have easily been trashed.

Comments

  1. jc says:

    now THIS is truly incredible service, thanks a lot, I’ll definitely try to use the panel from my old laptop eventually ! (it has LVDS too)

  2. rasz says:

    You can run those LCDs at full speed without any problems, you just need to either
    – bypass LVDS receiver chip on the panel, its the first IC after the connector.
    – use LVDS driver (can be salvaged from old GFX card/laptop for free)

    That way you bypass limited LVDS speed of the FPGA.

  3. Colecago says:

    I have an old LCD that needs the parallel version but can’t really find an interface board for VGA. I will probably have to just hook up some high speed parallel ADC’s.

    For all those wanting to go from vga straight to LVDS, look at ebay, lots of these things around

    http://www.ebay.com/itm/VGA-AV-S-VIDEO-controller-board-LVDS-TTL-LCD-panel-/280734369573?pt=COMP_EN_Networking_Components&hash=item415d128725

  4. Colecago says:

    Actually, answered my own question, that board also has TTL as well. Haven’t seen that before.

  5. Perry says:

    This is incredibly well timed as I have just recieved a broken laptop from a friend with a burnt out chipset…I’ll have to give this a try :)

  6. This is not (intentionally) SPAM. Just pointing out a way to save a whole lot of time (and cost) to drive LCD panels. I found the following on EBay… ;-)

    New LCD controllers $33 Ebay Buy-It-Now Free Shipping:

    http://www.ebay.com/itm/Compatible-R-RM5251-LCD-Controller-Board-Kit-DVI-/270802804706

    Available options:
    VGA
    VGA+DVI
    VGA+DVI+Audio
    VGA+TV
    Up to 1440*900
    Up to 1920×1200
    VGA, DVI

    USB programmer for above controller boards:

    http://www.ebay.com/itm/Programmer-Burning-LCD-Controller-Boards-Easy-DIY-/270814829935?pt=COMP_EN_Networking_Components&hash=item3f0dd25d6f

    • You tell them the panel resolution and they will program it for you, or you can buy the programmer youtself (2nd link above). Kit includes LCD controller board, LVDS and other cables, LCD keypad, backlight inverter (1-lamp, 2-lamp,or 4-lamp depending on specified preprogrammed LCD panel).

      Nice deal for under $33 shipped. Expedited shipping available (from China). Power cube, VGA and DVI cables available (cheap).

    • cutandpaste says:

      Very nice. I’d been looking for a low-cost source for something like this for quite some time, but hadn’t run across any that were less than several hundred dollars.

      Now, I can finally accomplish my goal of having small, high-DPI desktop displays (1920×1200 in 15.4″ form-factor) for cheap.

      • Joe says:

        Combine it with a frame buffer made using DRAM and you have a very nice display for those microcontroller projects that doesn’t cost an arm and a leg (or tons of CPU cycles). The DRAM will not need refresh and as an added bonus you get a lot more than the 512KB-2MB of the recent projects. Has anyone designed a shield for this? Preferably using a SODIMM?

      • no says:

        Not 2880×1800 or 2560×1600?

  7. Robot says:

    I have done something similar with LVDS transmitter from TI. Using the IC simplifies the VHDL code a lot!

    http://michaldemin.wordpress.com/2010/12/21/zx-spectrum-on-fpga-with-17-inch-lcd-screen/

  8. NATO says:

    “…LVDS is beyond the capabilities of simple microprocessors…”

    What an ignorant, uneducated statement. Differential signaling is well within the capabilities of any micro. TakeSingle input, single output. Have you ever heard of RS422? RS485? These differential signaling methods have been around forever.

  9. Danukeru says:

    On a sidenote, the information being sent is only on the rising edge of the clock.
    So the information could probably be sent on the falling edge as well, in order to send more commands to the screen.
    That’s a future solution I’ve already suggested to him.

  10. Atomhax says:

    I hope this leads to more hacked lcd screen tablets.

  11. bothersaidpooh says:

    Nice hack.

    Has anyone had any luck with the older variety of panels i.e. the ones on ancient Toshiba laptops?

    Someone should do a hack where the numerous otherwise useless LCD monitors can be hacked in this way, as I have a bunch of them here with non working main boards

  12. Joe says:

    Oh yeah, duh. There’s LVDS drivers with builtin frame buffers or DRAM interfaces. I was just hoping that there was some kind of way of recycling those old SDRAMs I have and 256MB sounds like a great addon to any kind of analysis tools. Imagine a bus spy using that for automobiles or an oscilloscope, for example.

  13. password says:

    i have a salvaged LCD too . I always wanted to turn it into an el cheapo oscilloscope with some very simplistic harwdare attached

    • Joe says:

      We could desolder some chipsets from dead laptop boards? And somehow get Intel to tell us how to program them using anything not made by Intel? LOL, that’s a little bit beyond my skills at the moment. A ‘little’ meaning years.

  14. NATO says:

    FYI, there are hundreds of projects like this on the ‘net, using FPGA’s, PIC’s, 8051 clones, you name it.

    This is nothing new, but I see a lot of surprised people here… Do you guys go anywhere other than this site? There are a lot of interwebs out there. I suggest you make good use of them.

  15. Microguy says:

    Nice hack. I’ve got several old laptops and I have been wanting to use them for some time.

    And unless that information just popped up NATO, it hasn’t been out there for some time. At least not in any format *I* have seen ad I’ve been looking for a while.

    Yes, I know a few bit have recently popped up, but it’s NOT like the internet is filled with these sites.

    I’ve been wanting to get into some FPGA too, so this looks like a good starter point. Haven’t seen how “cheap” that board is though.

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