Unable to connect to chip using SEGGER JLink after flashing firmware

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Sat, 22 Nov 2025 12:23:16 GMT

Here are the ripples on DEC4

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Sat, 22 Nov 2025 12:20:16 GMT

Still same behavior, getting failed to power up DAP with 1.3V supplied externally to DEC4

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Tue, 18 Nov 2025 07:42:13 GMT

Vout is around 1.8, voltage on reset is around 2.2

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Mon, 17 Nov 2025 14:48:56 GMT

I assume you measured it with a voltmeter. The DEC4 voltage will have ripple and is not constant value when DCDC regulator is enabled and you won't be able to measure this with a voltmeter so I can't tell if it is within spec or not. You also didn't answer my other question about the Vout voltage.

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Mon, 17 Nov 2025 14:15:54 GMT

I can try to supply the 1.3V externally,

Can you elaborate on how that would be different since I already get 1.25V on DEC4?

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Mon, 17 Nov 2025 14:07:03 GMT

Ok, but what Kenneth suggested was to apply voltage on dec4.

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Mon, 17 Nov 2025 14:00:20 GMT

I am unable to program the device, even when reset is held high

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Mon, 17 Nov 2025 13:34:08 GMT

Previously you mentioned that Vout was ranging between 1.7-2V, but now it's 2.25V? Can you try recovery method from Kenneth that I linked to earlier and re-program the device with a FW that does not enable the DCDC regulators?

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Sun, 16 Nov 2025 11:23:58 GMT

Dec4 : 1.25V

Dec1 : 1.08-1.13V

Reset pulled high with a voltage around 2.25V

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Tue, 11 Nov 2025 13:15:12 GMT

We've replaced the 100nf connected to Vnrf_out with a 4.7uf one

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Tue, 11 Nov 2025 12:45:55 GMT

Yes, I am using a SEGGER JLink Base for that.

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

PaKa — Mon, 10 Nov 2025 09:01:32 GMT

Just making sure you are using a proper SEGGER and not a DK for the programming.

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Mon, 10 Nov 2025 07:38:36 GMT

Please confirm which capacitor you replaced it with. Also if possible, please check the voltage levels on DEC1 and DEC4 with an oscilloscope or voltmeter, and/Or try the recovery method described by Kenneth in this post: RE: nRF52840 stuck after programming

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Sat, 08 Nov 2025 12:25:45 GMT

same behavior after replacing the capacitor

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Thu, 06 Nov 2025 08:55:07 GMT

Our reference design has 4.7 uF capacitor on vout, but it looks like your design uses only a 100 nF capacitor which could be a potential problem. The specification also states that the effective decoupling capacitance shall not be less than 2.7 uF:

Are you able to replace or solder on an extra capacitor on VOUT to see if it helps.

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Wed, 05 Nov 2025 11:46:40 GMT

and here the DTS file I created for it

it's worth noting I made the mistake of using the nrf52840DK board definition when flashing the first board
I am not sure if that could contribute to the issue but I was also able to flash it a few times before evenetually I can't connect to it and I keep getting the DAP powerup error

devzone.nordicsemi.com/.../8130.board.dts

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Wed, 05 Nov 2025 11:41:03 GMT

I only ordered two assembled boards, both are now bricked 😅

attached is an image containing the schematic for the nrf52840

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Wed, 05 Nov 2025 11:18:32 GMT

out of how many? Can you post the schematics for you board as well?

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Wed, 05 Nov 2025 10:38:16 GMT

I have encountered the issue on two boards,

I haven't tested with it disabled

I was able to determine that it's working by checking voltage out with a multimeter, powering the chip with 5V I get 1.7-2V out

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Wed, 05 Nov 2025 10:18:43 GMT

Have you encountered this issue with multiple boards, or just one? The behavior you see is typical for failing DCDC regulator. Have you tried to disable the DCDC regulator and how did you determine that the DCDC was working?

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

ubimiles — Wed, 05 Nov 2025 10:07:22 GMT

The design does indeed include the DCDC inductors.

I also ended up defining a custom board for Zephyr rather than using that of the nrf52840DK

RE: Unable to connect to chip using SEGGER JLink after flashing firmware

Vidar Berg — Wed, 05 Nov 2025 09:02:58 GMT

Hello,

Please check whether your design includes the optional DCDC inductors. The nrf52840dk/nrf52840 build target has this enabled by default, and if you run this firmware on HW without the inductors, the DCDC regulator will fail to provide a stable supply to the chips internal domains which can lead to issues such as being unable to re-program the device.

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/ref_circuitry.html

Best regards,

Vidar