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smatkinson1
1 Nickel

Latitude 5480 external displays using VGA and DisplayPort

Setup:

  • Machine is a Latitude 5480 with Intel HD Graphics 620 and a 1920*1080 built-in display
  • HDMI, VGA and DisplayPort USB-C ports
  • I am not using a dock
  • I am using a standard USB-C to DisplayPort cable and a standard VGA cable

 

Aim:

  • Run a projector via VGA connection to display a clone of the main desktop
  • Run a Dell external 22" monitor via DisplayPort via USB-C as an extended desktop

 

Problem:

  • Computer will only detect one of the displays at a time.
  • Both cables work perfectly on their own
  • Strangely, combinations of the other ports (VGA+HDMI, DP+HDMI) seems to allow for two or all three displays to function (with one cloned from the built-in display in the case of 3 displays).

 

Am I missing something? The manual appears to say nothing about the way ports work together.

Thanks in advance!

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1 Reply
jphughan
5 Rhenium

Re: Latitude 5480 external displays using VGA and DisplayPor

Based on your description, my guess is that the system is wired such that there are only two GPU output "channels" available to drive external displays, and one of them is dedicated to the HDMI output, while the other can be assigned to either the USB-C or VGA output at any given time, but it can't be split between the two to run them both.  I remember seeing something like this reported about an older Latitude system as well.  It's possible that the GPU itself (built into the CPU) has a limit on how many outputs it can support, so Dell may have had to implement this type of tradeoff in order to offer all 3 output connectors, and if so, frankly I think they made the right choice, because being able to run USB-C and HDMI together gives you more options than if VGA had always been available and you could only get either USB-C or HDMI running at any given time.

If I'm right, your options would basically be:

- An HDMI to VGA adapter
- A USB-C to VGA adapter and then running the 22" display via HDMI.
- A USB-A to VGA adapter (not ideal because it uses DisplayLink rather than a native GPU output, but it would work)
- A better projector that has an HDMI input, which will look better than analog VGA anyway.

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