SoftDevice fault on nRF52840 SD S140 v6.1.1

[PrFi]

Hello,

During application development I've got SoftDevice fault PC: 0x000251BA. It happens always just after start `FDS Garbage Collector`, so I expect that can be related to operations on flash. Could you let me know what causes fault from that address?

Device: nRF52840_XXAA

Softdevice: S140 v6.1.1

Regards,

Przemek

[Øyvind]

Hello, 

Could you let me know what causes fault from that address?

Your FDS Garbage Collector seems to collide with the SoftDevice radio timing. Please ensure that FDS_GC is not called within a radio timeslot.

Kind regards,
Øyvind

[PrFi]

Do I understand you correctly, that scheduling any flash operation is forbidden within granted timeslot (sd_flash_write and sd_flash_page_erase)? Where can I find documentation, which describe this limitation? According to the Info Center "SoftDevice timing-activities", I assumed that SoftDevice should take care about colliding activities. 

[Øyvind]

Have a look at Timeslot API timing and the Flash API timing in the SoftDevice Scheduling documentation. It also includes suggested intervals and windows.

I could not find anything saying that it's forbidden to schedule any flash operation within a granted timeslot. 

Kind regards,
Øyvind

[PrFi]

The code has been written according to documentation that have you mentioned. The weird thing is that the same code compiled on nRF52832_XXAA (SD s112 V6.1.1) doesn't cause any SD fault. Is it possible that this is a bug in the SoftDevice S140? 

[Øyvind]

No, this can be due to the difference in "Time to erase one page" in flash. 

nRF52832 Min 2.05, Max 89,7

nRF52840 Max 85

Difficult to say what can cause the issue. Are you able to share your code, so I can try to replicate the issue on an nRF52840 DK?