Displays We Love Hacking: LVDS And EDP

May 8, 2024 by Arya Voronova 20 Comments

There are times when tiny displays no longer cut it. Whether you want to build a tablet or reuse some laptop displays, you will eventually deal with LVDS and eDP displays. To be more exact, these are displays that want you to use either LVDS or eDP signaling to send a picture.

Of the two, LVDS is the older standard for connecting displays, and eDP is the newer one. In fact, eDP has mostly replaced LVDS for things like laptop and tablet displays. Nevertheless, you will still encounter both of these in the wild, so let’s start with LVDS.

The name “LVDS” actually comes from the LVDS signaling standard (Low-Voltage Differential Signaling), which is a fairly generic data transfer standard over differential pairs, just like RS485. Using LVDS signaling for embedded display purposes is covered by a separate standard called FPD-Link, and when people say “LVDS”, what they’re actually talking about is FPD-Link. In this article, I will also use LVDS while actually talking about FPD-Link. Barely anyone uses FPD-Link except some datasheets, and I’ll use “LVDS” because that’s what people actually use. It’s just that you deserve to know the distinction so that you’re not confused when someone mentions LVDS when talking about, say, industrial machinery.

Both LVDS and eDP run at pretty high frequencies – they’re commonly used for color displays with pretty large resolutions, so speed can no longer be a constraint. eDP, as a successor technology, is a fair bit more capable, but LVDS doesn’t pull punches either – if you want to make a 1024 x 768 color LCD panel work, you will use LVDS, sometimes parallel RGB – at this point, SPI just won’t cut it. There’s a lot of overlap – and that’s because LVDS is basically parallel RGB, but serialized and put onto diffpairs. Let me show you how that happened, and why it’s cool.

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Open Source Smart Display Takes The Long Way Around

July 31, 2019 by Tom Nardi 18 Comments

Thanks to the relatively low cost of the Raspberry Pi and high resolution LCD screens, “smart displays” have become a favorite project of those looking to clear out their parts bins. Just hook the Pi up to the screen, setup some software, and you’ve got yourself a digital bulletin board for your home that can show your schedule, the weather, etc. Build it into a mirror, and you’ve got yourself at least double Internet points.

But when [John Basista] started planning his own smart display, he decided to take the path less traveled. He’s entered the resulting open source project into the 2019 Hackaday Prize, and we’re very excited to see where it goes from here. Even in these early days he’s already made some great strides, with nary a Raspberry Pi in sight.

[John] has nothing against using the Raspberry Pi for these smart displays, and indeed, it has a number of traits which make it particularly well suited to the task. But the problem for him was that it only supported HDMI, and he had his heart set on using an Embedded DisplayPort (eDP) screen. Namely the Innolux N173HCE-E31, a 17.3 inch IPS LCD designed for laptops.

He tried to find a Linux or Android compatible SBC that featured eDP, but found it to be a challenge. There were some x86 options, but didn’t want to go down that road. Eventually he settled on the Dragonboard 410c, which features a quad-core Qualcomm APQ8016E CPU running at 1.2 GHz and 1GB of RAM. This board didn’t have eDP either, but it did have Display Serial Interface (DSI), which he could convert to eDP with the Texas Instruments SN65DSI86 IC.

From there, he started developing a PCB which would hold the Dragonboard 410c and the SN65DSI86. The board also breaks out I2C and UART so he can connect it to various other sensors and gadgetry down the road, and includes all the necessary power regulation to drive everything. The whole thing fits in the palm of your hand, and judging by the renders [John] has put together, should nestle nicely into the back of the 3D printed enclosure when everything is finished.

There’s still quite a bit left to do on this project, but [John] has plenty of time to tie up the loose ends. Currently there’s little information about the software side of things, but as you can see in the video after the break, it’s now running Android which should make things relatively easy.

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Put Those IPad Displays To Work With This EDP Adapter

July 18, 2019 by Tom Nardi 37 Comments

Regardless of how you might feel about Apple and the ecosystem they’ve cultured over the years, you’ve got to give them some credit in the hardware department. Their “Retina” displays are a perfect example; when they brought the 2,048 by 1,536 panel to the iPad 3, the technology instantly became the envy of every tablet owner. But what if you want to use one of these gorgeous screens outside of Apple’s walled garden?

As it turns out, there are a number of options out there to use these screens on other devices, but [Arthur Jordan] wasn’t quite happy with any of them. So he did what any self respecting hacker would do, and built his own adapter for iPad 3 and 4 screens. Not that he did it completely in the dark; his design is based on the open source Adafruit Qualia driver, which in turn was based on research done by [Mike’s Mods]. A perfect example of the open source community at work.

The resulting board allows you to connect the Retina display from the iPad 3 or 4 to any device that features Embedded DisplayPort (eDP). Rather than put a dedicated port on his board, [Arthur] just left bare pads where you can solder up whatever interface method your particular gadget might use. In his case, he wanted to hook it up to an x86 UP Core SBC, so he even came up with a seperate adapter that breaks out that board’s diminutive display connector to something that can be soldered by hand.

So what’s different between the board [Arthur] developed and Adafruit’s Qualia? Primarily its been made smaller by deleting the DisplayPort connectors in favor of those bare pads, but he’s also dumped the backlight control hardware and 3.3V regulator that in his experience hasn’t been necessary with the eDP devices he’s worked with. So if space is a concern in your build, this version might be what you’re after.

We’ve seen other Retina display adapters in the past, and of course the iPad isn’t the only high-end device that’s had a screen good enough to reuse on its own. The lesson here is that if you put a must-have feature in your product, don’t be surprised when some hacker comes along and figures out how to liberate it for their own purposes.

Hack A ThinkPad Display

February 21, 2019 by Al Williams 40 Comments

Hackers really like their tools. This leads to holy wars over languages, editors, keyboards, and even laptops. The problem with laptops is that they age, and not always gracefully. [Syonyk] likes his ThinkPad T430S, except for one thing, its TN display wasn’t really very good. These flat screens use an older technology and show color changes with different viewing angles among other problems. So he managed to upgrade the device’s screen to IPS with the help of a replacement screen and an adapter (see right). Apparently, many similar ThinkPads can take the same sort of upgrade.

The problem is that the laptop uses LVDS to talk to the TN screen, while newer screens are likely to use Embedded DisplayPort (eDP) which is a different protocol entirely. However, there’s now a converter that [Syonyk] found on eBay (from China, of course). For about $70, the motherboard’s LVDS output can transform to eDP. Of course, you also need an IPS display panel.

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Making A Thinkpad Great Again

August 26, 2016 by Brian Benchoff 42 Comments

The Thinkpad X220 is almost a perfect laptop. The X220 is small, light, was the last small Thinkpad to use 35W CPUs, has great Linux support, incredible battery life, and can be found used very inexpensively. For the Thinkpad Mafia, the X220 is a badge of honor, but it does have one glaring drawback: the LCDs in these laptops are capped at 1366×768 resolution.

A few wizards in Japan and China have taken up the X220 and developed an adapter to give this tiny laptop the display it deserves. Mentions of a FHD mod – the Lenovo-speak for a Thinkpad display upgrade – can be found on Taobao, but the anglosphere doesn’t get these cool toys. [Vectro] decided his X220 wasn’t up to snuff and decided to build his own Thinkpad mod to give his trusty companion a bigger and brighter display. He succeeded, and did it in a way that’s much better than any previous attempt.

Stock, the X220 uses an LVDS bus for internal video, and there aren’t enough lanes on this bus for a 1080 display. The usual way of modifying the X220 for a display with higher resolution is tapping into the eDP present on the Thinkpad dock connector. [Vectro]’s solution differs slightly from the usual way of doing things – instead of using an I2C EEPROM to report the resolution, DPI, and model of display, he’s using a microcontroller. This gives him the ability to control the power state and brightness level of the display. It’s a great solution, and is designed to be a relatively easy drop-in mod.

The new display works, and Thinkpadding at 1080 is awesome, but there’s still work to be done. The dock connector is incompatible with this mod, and hopefully scaling this up for small-scale production. Producing a few X220 FHD kits is going to be a problem, as each wire in the eDP cable is individually soldered to the connector. It doesn’t scale well, but there is certainly a demand to make the greatest Thinkpad even better.