Debugging external nrf52832 using nrf52 DK header P20 - Failing to connect

RE: Debugging external nrf52832 using nrf52 DK header P20 - Failing to connect

Mike N — Tue, 18 Aug 2026 20:38:22 GMT

Hi All.

I've reverse engineered another nrf52 dev kit which I know works with the particular external board I've got and I've now solved my issue.

As mentioned before, I was assuming a 6-pin SWD mapping like I've seen documented in multiple places. Like this:

Pin 1 -> VT ref

Pin 2 -> SWDIO

Pin 3 -> nRESET

Pin 4 -> SWCLK

Pin 5 -> GND

Pin 6 -> SWO

However, for whatever reason, the person who designed this particular external board decided to map the 6-pin contacts like this:

Pin 1 -> VT ref

Pin 3 -> GND

Pin 5 -> SWDIO

Pin 6 -> SWCLK

So the issue wasn't my nrf52 dk or my wiring or my J-Link software, but it was due to an unconventional layout of the 6 contacts. Once I rewired my board I was able to connect to it with J-Link Commander successfully first time. Even with the long cables and the breadboard I was able to connect using 4000 kHz so all is good.

Thank you Turbo J for your time and suggestions.

Mike

RE: Debugging external nrf52832 using nrf52 DK header P20 - Failing to connect

Mike N — Tue, 18 Aug 2026 10:22:59 GMT

Hi Turbo J. Thanks for your reply.

Yes good point about the Tag connect footprint being close to the processor pins. The board wasn't designed by me but I could raise it with them as they are very close together

I've eliminated the breadboard now and tried again using 500 kHz but still no luck:

SEGGER J-Link Commander V9.68a (Compiled Aug 17 2026 13:54:36)
DLL version V9.68a, compiled Aug 17 2026 13:53:37

Connecting to J-Link ...O.K.
Firmware: J-Link OB-nRF5340-NordicSemi compiled Jun 11 2026 13:12:28
Hardware version: V1.00
J-Link uptime (since boot): 0d 00h 01m 05s
S/N: 1050349361
License(s): RDI,FlashBP,FlashDL,JFlash,GDB
USB speed mode: Full speed (12 MBit/s)
VTref=3.300V

Type "connect" to establish a target connection, '?' for help
J-Link>connect
Please specify device / core. <Default>: NRF52832_XXAA
Type '?' for selection dialog
Device>
Please specify target interface:
J) JTAG (Default)
S) SWD
T) cJTAG
TIF>S
Specify target interface speed [kHz]. <Default>: 4000 kHz
Speed>500
Device "NRF52832_XXAA" selected.

Connecting to target via SWD
InitTarget() start
InitTarget() end - Took 117ms
InitTarget() start
InitTarget() end - Took 116ms
Error occurred: Could not connect to the target device.

I know someone who has an older version of nrf52 dk with a working setup for this external board so I'm going to use a multimeter on their setup to see if it's any different from mine.

In the meantime I'd be happy to try any other suggestions.

Thanks again

Mike

RE: Debugging external nrf52832 using nrf52 DK header P20 - Failing to connect

Turbo J — Tue, 18 Aug 2026 09:42:43 GMT

Try an SWD frequency of 500 kHz, those cables are rather long. I also recommend to eliminate the breadboard, these have terrible connection qualities here.

That Tag connect footprint looks extremely close to processor pins - you might cause unwanted shorts.