J-Link Programming external nRF52 : Failed to connect to target, no Idcode detected

[StephaneJ]

Hi,

I'm currently programming a custom board using a nRF52832 (using this wiring). Everything was working great but I tried to play with SAADC and maybe did a wrong configuration and/or added too much debug log. Since a previous code upload, I'm unable to connect to my board again.

I had another board with the same behavior (same code uploaded to confirm this was the code), but somehow I found a way to unlock it, I was able to upload a basic blinky example while removing the GND DETECT and switch from VDD to VDD nRF. I don't know if it related though.

But I still have one board completely locked, how to unlock it ?

> JLinkExe -device NRF52 -if SWD -speed 1518 -autoconnect 1

SEGGER J-Link Commander V6.22a (Compiled Nov 28 2017 17:57:01)
DLL version V6.22a, compiled Nov 28 2017 17:56:49

Connecting to J-Link via USB...O.K.
Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Jul 24 2017 17:30:12
Hardware version: V1.00
S/N: 682621274
VTref = 3.300V
Device "NRF52" selected.


Connecting to target via SWD
Cannot connect to target.
J-Link>

Thanks

[Garth@ESS]

Just in case it might help, I also had this issue, and eventually found that it was because the host processor (which communicated with the nRF52832 over UART) was holding the reset line low. Blanking the host processor solved the problem. Just another idea if people are troubleshooting this issue.