Problem with bootloader, SDK 14.2 and RC LFCLK

[jumpingfool]

I am experiencing a strange issue with the bootloader on my custom board in SDK 14.2.

Symptoms are that the board won't run until given an external kick - all it requires is JLINK to be connected once (not even debugger connected) and then the board runs and can be disconnected from the programmer.

If I flash just the application without the bootloader (so the Softdevice handles clock initialisation) then the board runs fine without the need for the initial JLINK kick.

I have eliminated a clock configuration issue - I've traced through the bootloader initialisation in the debugger and it is pulling the correct values to setup the RC LFCLK source from sdk_config.h when making the call to nrf_drv_clock_init.

My suspicion is that the clock initialisation code in the SDK 14 bootloader is missing a step necessary to start the RC oscillator. This wouldn't be immediately obvious on the DK board as the debug interface chip would generally be active/sending SWDCLK and this seems to be enough to kick the RC into life.

This is driving me crazy - any help would be gratefully received!

[Hung Bui]

Hi,

Would your application use the softdevice ?

Have you tested with a nordic ble example ? for example ble_app_hrs. Of course please edit it so it uses the internal RC LFCLK.

If you use an LED or UART logging, could you figure out where the code stuck ?

[Mario Dimitrov]

I Have experience the same thing with SDK 11.0.0 using nrf52832 

How to resolve this. 

[Hung Bui]

@Mario: Please try answer my above question. Also let us know if you can reproduce the issue by using our nRF52 DK .