[WIP] Making use of an LVDS laptop screen

A project log for All About Laptop Display Reuse

LVDS, eDP, connectors and controllers - let's learn it all

ArsenijsArsenijs 05/21/2021 at 11:440 Comments

! These are LVDS screen guidelines! For eDP screens, I'll have a separate guide later on =) !~

Fundamental ways to make use of a LVDS laptop screen

  1. Use a pre-configured and pre-wired "screen-specific" controller
    1. Should work out of the box - plug&play
    2. Might have multiple display inputs - in fact, there's a common board which has 3 separate inputs (VGA, DVI and HDMI), and they're all separate inputs you can switch between, effectively giving you a 3-input display for all of your tinkering needs!
    3. Most expensive option - in fact, prices vary wildly, you can be overpaying from $5 to $20 for a controller "programmed for" a screen that is not actually hard to program a controller for, -the eBay listing price can be increased because of the screen rarity or popularity, the firmware will be the same.
    4. Power requirements are prohibitive for portable projects - will typically need 12V, unless the board is tweaked for better power consumption
    5. These boards often use linear regulators heavily, so power consumption will be high and a lot of power will be wasted as heat, which is bad for battery-powered applications
    6. If there's only a "TV board" controller available, with antenna jack input and a USB port, these functions will consume extra power and might make your project's UX a bit worse
    7. Might have a speaker amplifier on it - if that's what you need, great, however, sometimes it'll just be another power-wasting addon
    8. CCFL inverters provided with these screens tend to be bulky, so harder to integrate in i.e. a laptop rebuild. It is likely that you'll be able to use the original inverter, though.
  2. Use a "universal" controller and wire it all up yourself
    1. Might need a bit of cabling work unless you buy suitable LVDS cables separately
    2. Universal controllers typically only have a VGA interface - adding a HDMI to VGA adapter will increase power consumption
    3. Using gertVGA adapter on GPIOs should negate some of that, but at cost of 20+ GPIOs
    4. Power consumption is still prohibitive because of the linear regulators, but can be tweaked if you add a separate DC-DC
    5. Both CCFL and LED (whichever you have) driving circuits will likely still need 9V+, however, with a separate step-up DC-DC or direct battery power, associated power losses can be decreased a lot
  3. Use a LVDS interface available on your SBC/FPGA/motherboard
    1. Is not always an option, sadly
    2. Will need some configuration research for your specific board
    3. Will need some wiring work, maybe even a custom PCB!
    4. Is very low-power! Your board's GPU will be doing most of the work
    5. Same as with the "universal controller" option, need to take care of the CCFL or LED backlighting

Is there a screen-specific controller available for your screen?

Looking up your screen's model number in the eBay search bar typically helps you find it.

Do you want to use one?

Reasons to use a "screen-specific" controller

  1. You want it to "just work"
  2. You want it to have multiple inputs
  3. Increased power consumption is OK
  4. You have the budget for it
  5. The possibly-present speaker amplifier is something you could make use of

Reasons to avoid using a "screen-specific"controller:

  1. The computer you're connecting to has an LVDS/TTL interface already
  2. You want to conserve some power
  3. You want to conserve some money
  4. You want to have fun and learn about laptop displays in the process
  5. This knowledge database project has a lot of info that will make it easier for you ;-P

In case of CCFL backlight, whichever out of these three options you pick, it is highly likely that you'll be able to reuse the inverter that came with the display originally.

Decide to use a screen-specific controller? Then go buy one! =D

[TBD] Proceeding with not using a "screen-specific" controller

So, you'll either use a universal controller, or some kind of LVDS interface present on your SBC/motherboard of choice.

What are the steps you need to take anyway?

  1. Powering the backlight - will help you determine if the backlight works and also help you check the screen for scratches. This step is optional, but will help you save money by not investing time&resources in a screen that migth be broken. If you know the screen to be working well, you can do this step a bit later.
    1. If the backlight is CCFL, you will likely be able to power it easily by reusing a laptop inverter [TODO: article]
    2. If the backlight is LED, then the LVDS signals and the backlight signals will be on the same cable. To test it, you will need to either solder 4 wires to the LCD screen controller board, or find a cable that plugs into the LCD and reuse that. [TODO: article]
  2. Figuring out the connector type [TODO: article]
  3. Figuring out the connector pinout - is likely to be one of the popular ones
  4. Finding/buying/rewiring a LVDS cable for your universal controller or motherboard - see the list of cables per pinout
  5. Connecting it all together, then powering it up and doing a "smoke test"