Unable to connect to Thingy:53 via SWD – error -102 during recovery

[KazuyukiYamada]

Dear Nordic Support,

I’m working with a Thingy:53 device and encountered a persistent issue during recovery. The device is recognized via J-Link (serial number: 1057760136), but attempts to connect to the application core (nRF5340_XXAA_APP) via SWD consistently fail.

I’ve tried:
- `nrfjprog --recover --coprocessor CP_APPLICATION --log`
- J-Link Commander with `connect` to `nRF5340_XXAA_APP`
- Verified USB power and cable
- Updated J-Link and nRF Command Line Tools

The error returned is:

ERROR: Encountered error -102: Unable to connect to a debugger. ERROR: JLinkARM DLL reported an error.

I’ve attached the generated `log.log` file for your reference.

Could you please advise on how to proceed or whether the SWD port might be permanently disabled?

Best regards,
Kazuyuki

[Kenneth]

Hello,

I assume you have connected the debugger cable to:
https://docs.nordicsemi.com/bundle/ug_thingy53/page/UG/thingy53/hw_description/program_debug_if.html 

Can you just check the supply voltage of VOUTB vs. SWDIO/SWDCLK voltage is the same? Also, can you double check that RESET is high?

Are you able to successfully connect the j-link to other targets than the thingy:53?

Kenneth

[KazuyukiYamada]

Thank you for your comment.

I have connected the Thingy:53 to the Debug Out port on the nRF54L15-DK using a 2x5 IDC cable, and the DK is connected to my PC via USB.

As you suggested, I will check the supply voltage. Just to confirm — do you mean to measure the voltage directly on the Thingy:53 while it is connected to the Debug Out port?

Best,

Kazuyuki

[Kenneth]

Hi,

One way or the other you need to check that the voltages on the two boards and pins are the same, preferably before they are connected yes (else the measurements may be wrong).

Kenneth