Programming prototype board from 52 DK

Question

I have a Nordic 52832 chip in an integrated module form from Fanstel. I have the NRF 52 DK, the Fanstel evaluation board, and a custom prototype board I built. 
 I can program the Fanstel evaluation board through the 52 DK with no problem. 
 The custom board runs the Fanstel module transmitting Bluetooth with default software installed on the module without problem. 
 I included a 6 pin Tag Connect interface on the custom board and am trying to load my program onto the custom board through the 52 DK but the board is not being recognized and instead commands from nRF Go Studio is writing the code directly to the 52 DK. The connections I am supporting are Vdd, GND, SWIO, and SWCLK. 
 My assumption was a hardware connection problem. The only possible errors being SWDIO and SWDCLK connections or the cable itself since Vdd and GND must be working or the chip would not transmit at all. 
 Traces seem fine and all pinouts correct. Anything else that could be causing the problem besides hardware connections?

hmolesworth · Answer

You probably have an issue with Gnd Detect, which is different from Gnd; this means 5 pins should be connected, not 4 as listed above. If your board is only connected to Gnd Detect (which is a "there is a custom board connected" sense line) with no separate connection to the nRF52 DK Gnd or vice versa then the custom board cannot be programmed as it is never detected. 
 The fix in this scenario is to connect together the nRF52 Gnd and the custom board Gnd - and also make the Gnd Detect connection between the two boards.

hmolesworth · Answer

It works for me with no changes to a nRF SD52 straight out of the box. P19 is not the same as P20, P19 uses EXT_GND_DETECT whereas P20 uses SH_GND_DETECT. Does it matter? Who knows, they go to different pins on the SAM Segger interface .. but see these photos, They shows P19 correctly programming a target board. When P19 is unplugged the nRF52 DK device is instead programmed. Why such a complicated set of adapters? Because I use 6-pin Tag Connect not 10-pin Tag Connect and we can't find a suitable single adapter. The equivalent Adafruit connector also shown with 4 wires plugged in as shown does the same job. All the grounds are correctly handled by connections on the adapters whichever of these two options you use. There are no modifications on any of these items.