I'm currently in the process of laying out a debug connector for an nRF52 chip. I'm planning on using the IDAP-Link. Most of the pins are pretty straight forward to connect (ie: for SWDIO I simply route that pin on the nRF52 uC to pin 2 on the debug connector). However I'm having trouble figuring out where to connect VTRef and Gnd Detect. With VTRef do I simply connect it to the same power source for my chip? I'm pretty sure this is the correct answer but I just want to confirm as this is my first time laying out a debug connector.

Secondly for the GndDetect pin, the documentation I've been able to find isn't very helpful. ARM's info center states that it can be used by the target system for debugger presence detection, but I can't find anything in the nRF52 documentation about where to connect it (I'd include a link but I'm limited to two due to my current reputation). Does the fact that VTref and GndDetect aren't in bold on the ARM infocenter mean that they're optional and don't have to be connected?


2 Answers 2


I've managed to figure this out with a bit of looking at ARM's documentation, in particular the page about the coresight 10 connector. VTRef is connected to the voltage powering the chip, and GndDetect is simply set to ground.

  • \$\begingroup\$ Do you know why it is called GndDetect? \$\endgroup\$ Commented Dec 8, 2020 at 19:59
  • \$\begingroup\$ Unfortunately not, it's been 4 years since I've worked on this project and I haven't looked at the documentation for any of Nordic Semi's products in awhile! \$\endgroup\$ Commented Dec 21, 2020 at 22:15

It's called gnddetect because the programmer has a circuit that, when that pin provides a ground connection, is able to know that it's connected to a target assembly.


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