U2719DC, XPS 15-9550, USB Type-C not working

@srknbdr  sorry for not seeing this earlier.  There are several threads confirming that the 9550 works fine with USB-C to DisplayPort adapters/cables.  I can't remember if I found one specifically relating to using such a cable/adapter with Dell USB-C displays, and I suppose it's possible that I only saw that confirmed with the XPS 13 9350, but given that they seem to behave identically in terms of the problem, I wouldn't expect them to behave differently with that cable/adapter.  I would argue that if you're otherwise stuck, it's at least worth the cost of an appropriate cable/adapter to test with, especially if you can return it, although again I have absolutely no expectation that you'll need to return it.

The KB should not be taken as an exhaustive list of possible fixes to this issue.  I even suggested adding Dell's own DA300 as a more portable workaround, especially for people who don't need to be able to charge their system via USB-C/TB3, but that doesn't seem to have been added.  And Dell Support reps unfortunately cannot always be relied upon to provide accurate answers to technical questions/problems, especially if Dell's documentation on the subject is incomplete or non-existent.  Those reps are expected to be broadly familiar with a broad range of product lines and have knowledge that will cover the majority of questions that will be asked by average users, most of which will be fairly simple.  If they're expected to have broad knowledge of a wide range of product lines, it's harder to have DEEP technical knowledge of specific areas, especially in cases like this where specific products have "quirks" that don't apply elsewhere.

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@srknbdr wrote:
Hey @jphughan, thank you for your response! The funny thing is, Dell Support told me that only these Adapters are supported by the XPS 9550: - WIRED,D3100 - TYPE C, WD15 - WD19TB,SALOMON - TB16, 130 WATTS - WD19DC,SALOMON First, they told me that only TB15 and TB16 will work, then they told me that only the 130W version of TB16 will work. In the end i asked why the cheaper WD15 wouldn‘t work. They were like ‚oh, you‘re right. 130W WD15 should do it. But at the start they were absolutely sure that only TB15 and TB16 would work. I think I‘ll get a dongle and just try it... but I‘m not sure whether to get the WD15 because a LAN Adapter would also be great. On the other hand I‘m not even sure how many years I‘ll stay with Dell.. everytime I do something I get problems. I really like their stuff but it gets frustrating...

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@srknbdr  wow, sorry to hear that it sounds like you got some seriously bad information.  Allow me to clarify/correct several things for you:

First, there's no such thing as a 130W version of the TB16.  The TB16 is available with 180W and 240W adapters.  The WD15 is available with 130W and 180W.  With both docks, you need the more powerful AC adapter option in order to use them with the XPS 15, i.e. the WD15 180W or TB16 240W.  Those higher wattage options for those docks exist specifically for systems like the XPS 15 that require 130W to be provided to the attached system.  With the lower wattage options, the docks only supply 90W to the attached system, which isn't enough for the XPS 15 to perform optimally.

The D3100 would technically work, but it won't supply any power to the system.  It's also an old model that has been replaced by the D6000, although the Dxxxx series docks typically aren't great choices for most people because they use DisplayLink technology rather than tapping into native GPU outputs.  I wrote about that in detail in this thread, specifically the post marked as the answer.

The WD19DC would technically work, but it's also unnecessary because it's designed for systems that require so much power that they need two USB-C connections to the dock.  Systems like the Precision 7000 Series fit that description, but not the XPS 15.  It doesn't even HAVE two USB-C ports.  The correct options in the WD19 family would be the WD19 180W or the WD19TB.  The latter comes standard with a 180W adapter, which apparently is enough to provide 130W to the attached system in the latest generation of Dell's Thunderbolt dock.  Those models are the replacements of the WD15 and TB16, respectively.

Dongles will work fine, even third-party dongles.  All of the non-video ports are just basic USB devices, and the dongles that also provide video outputs achieve that by tapping into DisplayPort Alt Mode, which is an industry standard and should therefore work on any system with a USB-C port that supports it, which the XPS 15 does.  The issue of this thread specifically with the 9550 and 9350 when using Dell USB-C displays is a huge anomaly.  In fact you could even use third-party DOCKS if it weren't for the fact that the XPS 15 requires more power than the USB Power Delivery spec officially supports (or I guess you could still use third-party docks if you were willing to plug the XPS 15's power adapter in separately from the dock.)  Anker makes some nice "mini-dock" dongles, but the Dell DA300 is actually a pretty compelling option due to its port selection, including a LAN adapter.  I have one and use it quite a bit.

Again, sorry to hear you got such bad information.  Also note that the adapters/docks that are "supported" isn't necessarily the same thing as adapters/docks that are "compatible".  There are likely a lot of accessories that work but that Dell itself doesn't officially support, although admittedly even that stance wouldn't account for the fact that even some official Dell docks that work with the XPS 15 weren't included in their list and some of the stuff they did include made no sense.

wow, I‘m glad I found some usable explanations through you. Dell Support phoned me today to ask if they can close the case. I said that I still couldn‘t find a solution. The guy gave me again several unsure answers and his source was always the guy working next to him......

I wanted to give the WD15 a try. I was almost ordering it on a Swiss website but the description stated that it only supports up to 30Hz. After contacting the support of the website they confirmed these informations. I came to the same conclusion on this thread (German): https://www.dell.com/community/Laptops/WD15-Dock-gt-4k-60-Hz/td-p/5233560/page/2 ; https://www.dell.com/support/article/de/de/dedhs1/sln304627/dell-dock-wd15-usb-typ-c-informationen-kompatibilität-und-technische-daten?lang=de

So the conclusion is that the only way to connect a XPS 15 9550 to a 4k monitor at 60hz is through a TB16 with 240W if I want to charge it simultaneously through the same cable.

Right?

Or I just use a Dongle (if yes, then probably the DA300 because of the LAN input), but then I still have to charge it ‚the old way‘ and there is no use in the USB-C speciality of this monitor for me.

I really do not want to spend another 300 francs in order to be able to get the originally promised 60Hz...

Maybe I should return the monitor and buy a cheap one when I‘ll get anyway almost the same results in the end. And later when I change my laptop to an uncomplicated (maybe not Dell this time) I‘ll get a better monitor.

Really, really a shame...

@srknbdr  if you want 4K 60 Hz and want to charge the system through the same connection, then yes your only options are the TB16 with a 240W adapter, or possibly the newer WD19TB that has replaced the TB16.  I don't know if that newer model will work with the XPS 15 9550, though.  I expect it will, but I haven't seen that absolutely confirmed anywhere.  That said, the WD19TB's key improvements don't really apply to the XPS 15 9550.  It can accept a DisplayPort 1.4 signal from the attached system, but your system only supports 1.2 anyway.  It's also backward compatible with regular USB-C (non-Thunderbolt) systems, but the XPS 15 9550 supports Thunderbolt.  Other than that, it's just got a slightly different port selection, a slightly different requirements about how certain types of display setups have to be cabled, and a modular design, although that last part is most relevant to businesses that have a lot of these, not so much for home users.  Also note that the WD19TB only comes with a 180W adapter, but on that model, that's enough power to provide 130W to the attached system.  I guess the WD19TB's own electronics are more efficient.

If you don't want a dock, the only way to get 4K 60 Hz would be through a USB-C to DisplayPort cable (or USB-C to HDMI 2.0 cable) attached directly to the system, NOT through any sort of multi-purpose dongle like the DA300.  If your display supports both DisplayPort and HDMI 2.0 inputs, I would choose the former.  The reason the WD15 can't do 4K 60 Hz is the same reason that the DA300 can't do 4K 60 Hz.  Very basically, if you connect a USB-C dock/device that wants to support both video and USB data traffic simultaneously, the available video bandwidth gets cut in half in order to allow for USB data traffic, hence 4K 30 Hz.  If on the other hand you use a video-only cable like the USB-C to DisplayPort cable I mentioned, then the full bandwidth of the USB-C connection is available for video.  If you want more details, I wrote a technical post about the various operating modes of USB-C and their impact on available video resolutions here, because this confusion comes up quite a bit.

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@srknbdr wrote:
@jphughanthank you again for the information. The store I bought the monitor from sent me a free usb-c to DP adapter. This is the explanation I was looking for! : [ Very basically, if you connect a USB-C dock/device that wants to support both video and USB data traffic simultaneously, the available video bandwidth gets cut in half in order to allow for USB data traffic, hence 4K 30 Hz. If on the other hand you use a video-only cable like the USB-C to DisplayPort cable I mentioned, then the full bandwidth of the USB-C connection is available for video. ] I‘ll try it with a dongle and if it works I‘ll get it replaced with a DA300, which has an additional LAN adapter. I‘ll keep you updated.

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@srknbdr   happy to help, but if you connect your display through a DA300, you'll be limited to 4K 30 Hz.  The DA300 itself supports 4K 60 Hz output, but that's only available when it's connected to a system that supports DisplayPort 1.3 or better over USB-C, and pretty much every system on the market right now only supports 1.2.  The reason is that no current Intel GPUs support anything higher than that, so the only systems where anything higher is available are systems that both have discrete GPUs (somewhat uncommon) AND have the discrete GPU rather than the Intel GPU directly wired to the display outputs (very uncommon).  This will start to change later this year when Intel's "Ice Lake" CPUs arrive, which will incorporate their new Gen 11 GPU that supports DisplayPort 1.4 over USB-C.  They should appear first in systems like the XPS 13, with the equivalent for the H Series CPUs used in systems like the XPS 15 arriving later.

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@srknbdr wrote:

@jphughan Sooooo the next problem is that I can‘t connect a network cable when I use a dongle. Somehow all the ways end up at TB16 240W.

can‘t believe it

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@srknbdr   I'm not sure what you mean when you say you can't connect a network cable when you use a dongle.  Do you mean that you want a dongle because you need to use a network cable, but the problem is that you can't use that dongle if you want the display setup you're trying to achieve?  In that case, consider getting a USB Gigabit Ethernet adapter that plugs into the system's USB-A ("regular USB") port, like this one.  That will allow you to have a wired network connection while keeping your USB-C port dedicated to video output and therefore able to run 4K 60 Hz.

@jphughan Sooooo the next problem is that I can‘t connect a network cable when I use a dongle. Somehow all the ways end up at TB16 240W.

can‘t believe it

srknbdr,

Click my name and private message me the monitor service tag number as well as your registered name, email address, and phone number.

Never considered this way, you‘re right. Thanks. (But: Yay, another dongle, good thing that I‘m trying to connect my Laptop through only one cable for everything).

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@srknbdr wrote:

Never considered this way, you‘re right. Thanks. (But: Yay, another dongle, good thing that I‘m trying to connect my Laptop through only one cable for everything).

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You're very welcome.  I know the dongles are annoying, but 4K 60 Hz simply requires a ton of bandwidth, so unless you want to go with a Thunderbolt dock, if you want both a high-bandwidth video signal and wired Ethernet, you'll have to run those over separate ports.  Good luck!

Tried the dongle, works fine. I‘m probably keeping the monitor and maybe I‘ll buy the docking station later.

Thank you very much again for your help and have a nice day!

Sorry to hijack this solved thread but I am having a similar issue, so might be better to keep all problems/solutions in one thread. I have an XPS 15 9550.

I have purchased a simple USB C to Display port to connect my 27" Apple Display, to no avail. It simply does not get detected.

I have also tried connecting this converter via a small USB C hub (which includes, HDMI, ethernet and a USB C port) but I get the same result.

Drivers are all updated but just about to update the BIOS. Any assistance would be appreciated.

Great thread.

I have the same issue. I am using XPS 9550 my wife uses 9350. We bought U2719DC only to use it with USB Type C. We will have to return this

In a meanwhile will use DP as temporry solution.