Hi everyone,
I am using the J-Link plus compact, and I am facing an issue regarding the reference voltage. The probe does not read the correct reference voltage and I cannot flash my boards because of a low reference voltage.
I have designed a custom PCB that integrates the nRF52840 SOC. I use the SWD interface to communicate the probe with the SOC and the system’s voltage is 1.8V.

The setup
I use a 20 to 6 pin adapter and a 6 Pin plug of nailto hardware connect the J-link with the PCB



Measurements
I have measured the VTref at both the PCB and the J-Link connector and I confirm that I read 1.8V. So, I am sure that I provide 1.8V as the target reference voltage to the J-Link.
However, when I run the J-Link commander the reference voltage varies. I have measured three cases and the VTref varies from 1.451 - 2.046V. However, when I measure with the multimeter I measure 1.8V for each case:

No connection of J-Link with the target (from SES)


Connection of J-Link with target (from SES)




When enter the debug mode from SES


Just for reference, this is my PCB schematic and layout for SWD interface

You are right!! It works now!! Thanks a lot!!