Programming external board from nRF51-DK / nRF52-DK stopped working

[jdog]

So in our factory I had setup both an nRF51-DK (PCA10028) and nRF52-DK (PCA10040) to program our external boards we are producing which has a NRF51822-QFAB-R7 populated on it. Using nRF Connect Desktop (v3.1.0) Programmer (v1.2.0).

The external board was powered externally and I had hooked up the dev boards like so (click to enlarge):

This was all working fine so I left it at the factory a few days later they called to say both units weren’t programming.

The nRF51-DK would only read the nRF chip on the dev board.

The nRF52-DK would get stuck on “Using nrfjprog to communicate with target”, if nothing was connected it would read the nRF chip on the dev board. So slightly different issues but neither would program the external boards anymore.

I updated the J-Link OB interface bin on board dev boards to the latest on Nordic’s website (170724). But that had no affect.

I tried changing the wiring so the external board was powered via the dev kits like this diagram (click to enlarge):

However same issue. Tried using nrfjprog commands like —recover, —debug reset, —reset etc. But still nothing. Any clues what has gone wrong or what else I could try?

Also is using a dev board the most robust way to program custom devices at the factory or are there other more reliable tools I could use?

Currently production has stalled so any quick ideas appreciated. I have more nRF51-DKs on order to try with fresh boards to see if the issue is with them.

[haakonsh]

I'd start by measuring the voltages of VDD and VTG and scope the SWD/SWDCLK lines. 

Our DK's are not intended to be used for production programming, the J-LINK OB debuggers do not include a license for production programming, only for development. 

I suggest you look into SEGGERs line of production programmers as they are created for the purpose of flashing countless devices without breaking, and it has the proper license ofc.

[jdog]

Okay thanks will look into getting a J-Link Plus with J-Flash (I assume that is what we need), just concerned we will have the same issue.

I just received a new nRF51-DK and the same thing is happening. This is with a prior known good board which I have programmed before.

I checked VDD and VTG and the voltage was good. I don't own a scope so can't look at the SWD lines unfortunately. Racking my brain as what has changed. It gets stuck at "Using nrfjprog to communicate with target". Are there any commands I can use with nrfjprog to try and narrow down the issue?

[jdog]

Okay just got it working with the new nRF51-DK. Still not sure what is wrong with the other two dev boards. Very strange.