NVMC Controller never gets ready when trying to flash nrf52840 custom board

[ubimiles]

I have ordered two boards using the nrf52840

I was able to flash the first board and my firmware is working as expected 

however whenever I try to program the other one I get the following error 

[error] [ Client] - Encountered error -220: Command program_file executed for 30036 milliseconds with result -220
[error] [ nRF52] - NVMC controller never gets ready.
[error] [ nRF52] - The write access failed, but no cause could be determined.
[error] [ nRF52] - It may be due to an unaligned access, accessing a nonexistent memory, or a communication issue.
[error] [ nRF52] - Failed while performing 'Write' operation on target address 0x0000C000.
-220: Encountered exception while waiting for nvmc to be ready after configure for write.
[error] [ nRF52] - Failed while reading device information.
[error] [ Worker] - Encountered exception while waiting for nvmc to be ready after configure for write.
ERROR: Operation failed due to timeout. Check the log messages for more details.

two boards are identical. 

[Sigurd Hellesvik]

Hi,

These are custom boards right?
What do you use to program them?

What voltage are they powered by?

Regards,
Sigurd Hellesvik

[ubimiles]

Hi Sigurd, 
yes they are indeed custom boards, 
I am using a SEGGER JLink Base, 
I have tried powering them on in both normal voltage and high voltage mode (~3.6V/~5.5V)

I do have two boards, 
each with two nrf52840 chips 
nrf52840-QIAA-T and nrf52840-CKAA-R

the two nrf52840-QIAA chips are behaving as expected
one of the two CKAA chips is erroring out with the NVMC error

[Sigurd Hellesvik]

The first thing that comes to mind is that perhaps the debugging interface is not connected properly on the faulty device. For example a bad soldering.

Could you take oscilloscope readings from the SWD lines of both the working PCB and the faulty one, so we can compare them?