RE: BLE SDH observer interrupt level

Einar Thorsrud — Wed, 07 Sep 2022 13:41:13 GMT

Hi,

You are right that there are different interrupt priorities for the SD_EVT SWI between some SoftDevices, and there was also a mismatch with what was used by the SoftDevice and what was documented in the SoftDevice specification (this was a bug). In SDK 15.0.0 there is code manipulating this in swi_interrupt_priority_workaround() in <SDK15.0.0>\components\softdevice\common\nrf_sdh.c for all SoftDevices except S140, which sets the priority to 7. This was changed in SDK 15.2, and you can find a brief mention of it in the release notes:

Removed the workaround in nrf_sdh.c overriding the default priority level on SWI interrupt SD_EVT_IRQn and RADIO_NOTIFICATION_IRQn used by the SoftDevice.

The SoftDevice priority is 6, and that is intentional. This is also mentioned in the release notes of SoftDevice S132 6.1.0:

Fixed documentation for SD_EVT_IRQHandler and RADIO_NOTIFICATION_IRQHandler, where the default interrupt priority was documented incorrectly (DRGN-10174).

So, for the questions:

[quote user=""]1) Is this difference in behaviour intentional? If not what might be the factors involved in determining the interrupt priority?[/quote]

No. It was a bug. The priority should have been 6.

[quote user=""]2) Is there a recommended/official way to configure the interrupt level these events will come from?[/quote]

You can use sd_nvic_SetPriority() to change the interrupt priorities of the SoftDevice, as done in the implementation of swi_interrupt_priority_workaround(). This is not normally something you should do with the SoftDevice interrupts, though