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I have a Dell U3219Q monitor which has a USB hub and KVM integrated into it. When I connect it to my Windows 10 PC over either the USB-C or USB-A cable the USB connection is intermittent somehow. The mouse and keyboard randomly drop input for a second or two, and the DAC for my headphones errors and disconnects. The webcam seems to work fine.

When I connect the same USB-C cable to my Macbook Pro they all work perfectly. The peripherals also work perfectly in Windows when connected directly to the PC.

The PC is a desktop with a Z390 Aorus Pro Wifi motherboard. I've tried connecting to several different USB ports as well as updating Windows and the motherboard firmware; no improvement.

Anybody know how I can debug the USB connection and figure out what's happening? What drivers might need updating to get the hub to work better, like it does on a mac?

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  • Do I understand right that the flaky connection is PC-KVM-monitor, but is fine for PC-monitor? In that case, could you try another KVM?
    – harrymc
    Commented May 18, 2021 at 8:39
  • The KVM is part of the monitor and I don’t have another. Keyboard, mouse, webcam plug into the USB ports on the monitor. Monitor has two USB uplink cables, and I can choose which is paired with each video input. So my windows desktop is connected over DisplayPort and the USB-A uplink, and the MacBook uses a single USB-C (thunderbolt) connection to send video and receive all the input from the peripherals. So if I plug in the laptop the monitor automatically comes in and switches inputs. But monitor -> PC is flaky regardless of which usb uplink I use.
    – jtb
    Commented May 19, 2021 at 12:54
  • 1)How often does the issue happen with the PC? ex: every 5min, once a day, etc. 2)Does the issue happen if JUST the PC is plugged into the monitor & the second PC is disconnected? 3)Have you contacted Dell? I wonder if there is a FW update for the monitor, the support page doesn't seem to work for that monitor else I'd check
    – gregg
    Commented May 19, 2021 at 19:56

2 Answers 2

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+300

Here is a link to the manual, pg58 shows the KVM function. Which appears to simply be a USB hub with two up-links: USB-C & USB-B (goes to USB-A) so I guess when you switch the monitor input it switches the hub uplink.

  1. Since it appears to be a glorified hub I wouldn't think you'd need a hub driver, I can't find a driver for it on dells site.
  2. Only other thought is if you updated Z390 mobo UEFI/BIOS (latest=F12k) then I'd also update its USB drivers, but I couldn't find those. Might want to update the 'Intel Serial I/O driver'. I also saw a 'USB Blocker' under Utilities, not sure what that is about, but you likely don't want that

How often does the disconnect/flakeyness happen? Could you see if it happens in the BIOS? Or a linux live CD/USB session? This is a technique HW vendors confirm if Windows or its drivers are causing the issue vs a HW problem

--EDIT

I found some things that might be useful with my google-fu (U3219Q update site:dell.com):

  1. More manuals, one of the manuals (pg6) mentions a 'Dell Display Manage' program that lets you control the input within a PC (vs monitor OSD menu) that indicates a HOTKEY combo that can trigger it. So maybe you are hitting that hotkey triggering the KVM & when the second macbook isn't connecting it just switches back to the PC. I'm not sure IF a default hotkey is setup or that the below picture is the default. enter image description here

  2. Driver tab isn't working, but google found two monitor FW updates:

  3. Troubleshooting guide specific to this monitor model shows how to factory reset it which I'd try.

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  • RE timing: It really varies which has given me false hope that it was fixed several times. Typically it's pretty bad, maybe an 800 ms input pause every 5-25 seconds. I'm timing it now and it's been fairly consistently better over USB-C (so plugged into GPU) than I had noticed before.
    – jtb
    Commented May 20, 2021 at 18:08
  • 800ms pause only, that might be hard to troubleshoot, I thought you were talking multiple seconds at least. I can appreciate though any delay happening often could get annoying. You haven't noticed it with any particular key combination as I noted in #3? Did you try #4 FW update? #5 factory reset monitor?
    – gregg
    Commented May 21, 2021 at 13:22
  • #3 no, it's not a key stroke, I test it by just moving the mouse in little circles and waiting for the hitch. Or typing an ordinary sentence and at some point a keyup event will get dropped and it will act like I'm holding down one of the letters. I updated the Monitor firmware and Intel Serial I/O driver, rebooted everything, but still no change. Then yesterday I tried a bunch of different USB ports and found one that seemed to work well! ...but then I went back to a port that was misbehaving and now that one is working too... so it feels like a temporary lull but I can't repro right now.
    – jtb
    Commented May 21, 2021 at 23:12
  • Well, it's still working! It was messed up, I switched USB ports twice and it remained messed up, tried another and it worked. And a couple days later it's still working on all the ports. I feel like I'm missing something key here, but this is the first time I've had it working in a long time, after following your suggestions. So thanks for all your help @gregg; I will and give you the bounty, even though I'm not sure which step precisely might help the next person with this exact problem.
    – jtb
    Commented May 24, 2021 at 22:45
  • Well, after a reboot but no other changes I can think of the hitches are back. Interesting that it's intermittent somehow. Guess I'll try the swap-to-lots-of-ports trick to see if that triggers anything again.
    – jtb
    Commented May 27, 2021 at 16:26
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The Dell UltraSharp U3219Q Monitor User’s Guide describes a setting that might relate to the delay problem, called Response Time:

enter image description here

It's probably currently set to Normal, at 8 ms. Try to toggle it to Fast, 5 ms.

If that doesn't improve the problem, there are Windows drivers and firmware that you could download from Support for Dell U3219Q | Drivers & Downloads.

If nothing helps, I would suggest contacting Dell Support as last chance.

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    I suspect thats related to the video/display/LCD timing, but never hurts to try especially considering there is a KVM/superhub in it
    – gregg
    Commented May 21, 2021 at 23:56
  • Yeah, no change here except for introducing some odd ghosting artifacts. Switched it back to Normal :) But worth a short
    – jtb
    Commented May 24, 2021 at 22:46

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