NRF_SDH_CLOCK_LF_SRC Changes Break app and DFU in 15.3 (from 15.2)

[dmacpro91]

I've finally worked around some funky bugs that only appeared after updating to 15.3. In my app, I had to change my clock source to RC or SYNTH to make it work (was hanging on enabling the softdevice). My XTAL setting worked fine in 15.2. When I got to working with DFU, I had some issues and tried everything mentioned on here (mergehex to fix the UICR/MBR bug, fixing the Makefile, etc.), but still couldn't get the DFUTarg device to appear. Loaded the debug version of the DFU module and stepped through it to find it failed to execute past the command to start the softdevice. It dawned on that this was probably the same issue that prevented my app from executing. After changing the clock source, everything worked as expected.

Now my question: What changed that makes the XTAL clock setting work fine in 15.2, but not 15.3? I'm using the DVK-BL652-SA device from Laird. Is there any issue using the SYNTH clock setting if power consumption isn't really a concern?

[Simonr]

Hi

This could be because you've not included the nrf_drv_clock.c in your project, as that file is used to define NRF_CLOCK_LFCLK_XTAL as CLOCK_LFCLKSRC_SRC_XTAL in SDK v.15.3, while SDK v.15.2 uses nrfx_clock.c instead. If that's not it, I'll need some more information about your application. Is it based on one of the SDK v.15.2 examples, and if so which one?

If current consumption isn't an issue, there shouldn't be any problem using the LFSYNTH. This way, the clock will have the accuracy of the HFCLK you're using, so keep in mind that the external HF clock has way better accuracy than the internal one.

Best regards,

Simon

[dmacpro91]

Thanks for the reply.  Initially when migrating to 15.3 from 15.2, I started with the stock 15.3 bootloader example.  Even this example showed the issue with the softdevice not launching on my end.  I'll test your suggestion and reply back later.

My projects were all based on 15.2 examples.  Mainly the ble_app_uart one.