[rockitdoc]

The harness has a USB cable coming from it. Is this an input TO the HDX or an output FROM the HDX?

 

[N890GF]

This is an input TO the display. Its basically a third USB port like the two on the back of the case.

EDIT: apparently that third USB on the harness is no longer supported...no wonder it wasn't working for me the last couple months of testing...

 

[RV8JD]

That USB cable on the harness didn't always work reliably, so Dynon removed it from later HDX units. See post #9 by Dynon on their forum:

https://forum.flydynon.com/threads/displey-sv-harness-d37-usb-removed.14796/​

 

[wirejock]

Usb

Mine doesn't have it. Just the two ports on each HDX. One each has the Wifi adapter. The second on each goes to a two port USB on the panel.