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Latitude 7480 External Displays

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Hi there,

I wanted to know if Latitude 7480 can support USB Type C adapter to HDMI.
If not, can it support USB Type C adapter to DisplayPort?

Also, is multiple external displays supported (extended mode- 2 monitors)? (1 from the hdmi port + 1 from the USB Type C port with an adapter).

Thanks,

lijjo

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4 Replies
Community Manager
Community Manager

RE: Latitude 7480 External Displays

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Hi lijjo,

Thanks for posting.

Here is some information you may find helpful:

http://dell.to/2xmOTJp

http://dell.to/2xmARYd



Dell-Robert P
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#IWork4Dell
To help us troubleshoot, please send us the Dell service tag number via a private message
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jphughan
5 Rhenium

RE: Latitude 7480 External Displays

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Yes, it will support USB-C to HDMI or DisplayPort cables/dongles.  You could even use a dongle plus a DisplayPort MST hub in order to drive multiple displays off of that single USB-C port if you wanted to, and you'd be able to run display configurations that were within the bandwidth of a single DP 1.2 output, which is enough for 4x 1080p displays or 2x 1600p displays. However, you also have to stay within your GPU's display max, which is 3 on that system.  Note that the configurations I just described would NOT be possible if you were connecting through a USB-C DOCK, since in that case the dock would be using the USB-C port for both display and USB data, which cuts display bandwidth in half.  This is why USB-C docks only handle 2x 1080p.

Additionally, if your 7480 has Thunderbolt (which is optional on that model), then after installing the latest BIOS and Thunderbolt firmware update, you could also use Thunderbolt 3 to Dual DisplayPort adapters.  That solution is even better because Thunderbolt would give you the bandwidth of TWO full DP 1.2 outputs rather than one, so you could for example run 2x 4K displays.

And yes, using USB-C and HDMI simultaneously would also be fine.

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RE: Latitude 7480 External Displays

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Thanks for replying.

Robert - I already saw that info but it doesn't answer my question.

jphughan - I have a USB-C to HDMI dongle("GoldTouch" company) and the laptop doesn't detect it -

"Unknown USB Device (Port Reset Failed)"

Are you sure that it does support USB-C to HDMI?

And my BIOS and Intel HD Graphics driver are up-to-date.

Because specs only show USB-C to DP

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jphughan
5 Rhenium

RE: Latitude 7480 External Displays

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I can't speak to the dongle you're using, and I admittedly can't test this myself at the moment, but I believe that a dongle that ONLY offers USB-C to HDMI (or any other video format) shouldn't even be detected as a USB device.  USB-C ports that support DisplayPort Alternate Mode, such as the 7480's, achieve it by having a native GPU output wired directly to the USB-C port, and as such, dongles don't need to have a presence on the USB data bus and therefore (I believe) wouldn't need to be detected as a USB device even temporarily.  If on the other hand the dongle you're using has HDMI as well as other things like Ethernet, audio, another USB connector, etc, then that might explain the error you're seeing.  But even in that case, you still shouldn't be seeing Device Manager errors about the dongle. That suggests an issue with either that dongle or the drivers on your system, potentially an incompatibility with some other driver or application that interfaces with the USB stack.  Older versions of Citrix Receiver have been known to interfere with USB traffic on Dell TB16 docks, as an example.

In terms of HDMI not being listed, that's completely expected and completely unimportant.  The only type of video output that USB-C supports NATIVELY is DisplayPort, and that capability is optional -- though again, it's included on the 7480. However, as you've found, there are dongles to adapt USB-C to HDMI and VGA, which is possible because the dongle converts that DisplayPort signal to whatever output is needed.  The system doesn't care and in fact doesn't even know this is happening; from its perspective, it's just sending a DisplayPort signal.  And every USB-C to HDMI dongle operates this way, because there is no such thing as a USB-C output that supports HDMI natively, or any other non-DisplayPort video signal.

So yes, I'm sure USB-C to HDMI adapters in general work on this system because USB-C is a standard and the 7480 includes a video-capable implementation of that standard.

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