nRF52840-PDK "Debug In" VTref problem

[garrulous]

Hello,

May I please check if the following is correct?  On the nRF52840-PDK board (v0.9.3, 2017.47), the "VTref" pin of the "Debug In" header is connected to VDD.  Should this instead be connected to VDD_nRF, to track the nRF52840 supply voltage?

For our project, we are powering the board from an external 1.8V supply (via header P21), with:
1. "VEXT->nRF" switched "on", and
2. "nRF Only/Default" switch set to "nRF Only".

In this configuration, the on-board debugger is disabled and an external debugger is required (e.g. J-Link).

"VTref" (VDD) appears to float until we connect a USB cable, at which point it equals 3.0V.  This will cause the external debugger to use 3.0V logic-levels to communicate with the 1.8V-powered nRF52840.

Is my understanding correct?  Is it worthwhile to break the track connecting VTref to VDD, and hand-solder a connection to VDD_nRF?

[MartinBL]

Hi,

Is it worthwhile to break the track connecting VTref to VDD, and hand-solder a connection to VDD_nRF?

This is the easiest way to do it. Unfortunately you have found a usecase we didn't think of, and there is no better way. 

[garrulous]

Thanks Martin.  No damage appears to be being done; if re-work by hand is too difficult might just leave it for now.