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I have a 27 inch display LG27UD88-W which has two built-in USB 3.0 ports.

As far as I understand they should work out of the box if I connect my video card with the screen by DisplayPort.

Unfortunately, my computer does not recognize any USB device when plugged in to the screen ports. Mouse and keyboard didn't react neither. Is it possible that my video card does not support it or that a driver is missing? Or is it a defective screen?

My system: Windows 10 Pro, NVidia EVGA 980 Ti with multiple 4K screens connected by DisplayPort.

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  • Is the model number correct? Web search shows no such thing. Please correct your question.
    – Ale..chenski
    Oct 20, 2016 at 0:54
  • @AliChen indeed, that was a typo which is corrected now!
    – andreas
    Oct 20, 2016 at 13:49
  • 4
    "multiple 4k screens" - living the dream.
    – Journeyman Geek ♦
    Oct 22, 2016 at 1:02
  • @JourneymanGeek indeed, it is totally awesome! After having enjoyed Macbook Pro with "Retina" display in the past, I find Windows 10 even more enjoyable now with 4K screens. I would definitely recommend them to anyone, for your eyes' sake. ;-)
    – andreas
    Oct 22, 2016 at 1:10
  • I do dual 4k and it's awesome
    – Journeyman Geek ♦
    Oct 22, 2016 at 1:51

4 Answers 4

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Your understanding is incorrect. There is a USB hub in your monitor, no different than an external USB hub. You need to connect a USB cable from your computer to the USB in port on your monitor and that will allow USB devices to work from your monitor.

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  • 7
    Oh really? I thought DisplayPort is capable of transporting USB traffic as well. Thanks for fixing that misunderstanding! I am just not sure why having two ports when one has to be used for the incoming traffic... For clarification, the screen has one more USB-C port, but that's it then.
    – andreas
    Oct 19, 2016 at 23:48
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    As my comment to @Ali Chen's answer states, lg.com/us/monitors/lg-27UD88-W-4k-uhd-led-monitor suggests that data transfer and display using USB-C will work. You might want to clarify this, as your answer seems to suggest - though not stating it directly - that USB has to be an addition to DisplayPort.
    – I'm with Monica
    Oct 20, 2016 at 8:57
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    @andreas displayport's Aux channel has enough bandwidth to carry a USB2 signal and the specification allows for doing so; but I'm not aware of any implementations that do so.
    – Dan Is Fiddling By Firelight
    Oct 20, 2016 at 14:41
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    @andreas Humans are capable of giving birth and running a mile in under four minutes. That doesn't mean that I can do either of those things.
    – David Schwartz
    Oct 20, 2016 at 19:22
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    Another difference is that "DisplayPort" is NOT designed to carry USB signals; Apple uses Thunderbolt to carry DisplayPort+USB (Thunderbolt was designed to be backwards compatible, and is port-compatible), but that doesn't mean a mini DisplayPort connector can or will provide USB.
    – Doktor J
    Oct 20, 2016 at 21:01
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The LG27UD88 monitor is indeed a piece of confusing engineering. You have too many options.

  1. If your video card does not have the Type-C output and you are using DisplayPort, the DP link does not have the USB capability. The Type-A USB3.1 receptacles will not work unless you connect the LG Type-C port via additional C-C cable (to Type-C host) or C-A cable to a regular USB-A host port.

  2. You can connect the monitor via Type-C port to a Type-C host (using C-C cable), if the host supports Display Port video over Type-C. But then you will need a very special support from host to have USB functionality, because the cable can do either USB, or DP @ 4K resolution,[see correction/clarification below].

  3. You can use HDMI ports, then #(1) still apply.

The monitor also has tremendous number of options to charge smartphones, but I was lost there.

Enjoy your nice 4K monitor.

TECHNICAL CLARIFICATION: Thanks to comment by Alexander Kosubek, a full-featured C-C connection can support both USB3 (taking two diff-pairs in the cable) and a two-lane DP. However, to support 4K display resolution, the DP must be revision 1.3, while the LG27UD88 can do only v1.2. More, both display and PC host must support a "Type-C alternative mode" as "USB DisplayPort Dock", which implies full support for Power Delivery function, which is needed for proper discovery of Type-C partner. In all cases the USB2 link is supposed to be functional, although it is unclear how it is used in the display. If this makes the use of LG display any less confusing, then this is it.

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  • lg.com/us/monitors/lg-27UD88-W-4k-uhd-led-monitor suggests that acutally a single USB-C cable will suffice for data, visual and charging at the same time, thus contradicting the last claim of your 2nd option.
    – I'm with Monica
    Oct 20, 2016 at 8:53
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    Tricked by marketing! I honestly thought that USB would be possible on the screen through DisplayPort connection. DP could transport USB data, but my LG does not use this capability. Now I have an issue because my computer is quite far away from the display. While my DP coords are long enough (~2m), I am not sure if USB even supports such lengthy coords. But beside that, it is still an amazing screen, of course.
    – andreas
    Oct 20, 2016 at 13:53
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    @andreas USB3 A/B cables are available in well beyond that length, I was able to find them in 15ft/4.5m length on Amazon. I didn't see any USB-C cables longer than 2 meters.
    – Dan Is Fiddling By Firelight
    Oct 20, 2016 at 14:52
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    @andreas: I can't say for sure whether your monitor would pass USB over the DisplayPort cable, but it is 100% certain that your GeForce 980 knows nothing about USB.
    – Ben Voigt
    Oct 20, 2016 at 15:56
  • According to Type-C specifications, practical length for full-featured cables at SS Gen1 speed (5Gbs) is under 2m, which is based on "cable performance requirements", and <1m for Gen2 speeds. Historically it was a challenge to keep signal attenuation and jitter low across even 1-2m cables. I don't know what Amazon is selling, but I would be extremely skeptical.
    – Ale..chenski
    Oct 20, 2016 at 16:48
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From LG's website "The USB port on the product functions as a USB hub. Please connect the USB C-C or USB C-A cable to the PC"

You will have to connect this cable before those ports will work as a hub!

Link to manual (your info on page 17) here

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    I have just found it as well in the moment you have answered, thank you!
    – andreas
    Oct 19, 2016 at 23:52
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I have this screen attached to my MacBook Pro USB C-C cable. I had to turn off Quick Charge in the screen menu before the USB hub functionality would work (ie: before my iPhone plugged in via lighting to USB 2.0 cable into the screen was picked up by my Mac over the UCB C cable).

This was mentioned in the manual Captain Gerry linked above.. can't believe I did not RTFM first! Do'h

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