Best practice for when to enable SoftDevice (sd_* vs. NVIC_*)

[ned_zeppelin]

The issue is that if a peripheral needs to enable interrupts (or anything else partly protected by the SoftDevice) and is configured before enabling the SoftDevice, the NVIC_* functions must be used in the initialization and the sd_* functions for disabling/de-initialization. This can quickly lead to strange code and unforeseen bugs. The same is true for using the sd_mutex* etc.

So what is considered "best practice" for this issue when using the SoftDevice?

My initial thought would be to enable the SoftDevice immediately after initializing clocks and anything else that the SoftDevice might be depend on, and always use sd_* everywhere. And wait to enable the device manager, advertising, etc. until it makes sense to do so.

This does make debugging a bit more problematic. But are there any other drawbacks that I am missing? Or does anyone have a better approach?

A define to indicate if a SoftDevice is used could be added to make drivers etc. more general, but for BLE-centered applications this define would need to be checked quite a lot of places.

[Hung Bui]

@ned_zeppelin: From my point of view:

• If you don't have to use the interrupt/peripheral that is partly protected by the softdevice before the softdevice is enabled, you should enable the softdevice first and enable the interrupt using sd_* function.

• If you need to use the interrupt before the softdevice is enabled, you can use NVIC_* function. However, when you enabled the softdevice, you would need to reconfigure the interrupt using sd_* provided functions. This mainly is to avoid your interrupt priority violated with the priority levels reserved for the softdevice.

[Hung Bui]

@ned_zeppelin: Sorry for the late response. I was checking with our SDK team. Currently we only use the preprocessor flag SOFTDEVICE_PRESENT to detect if the driver should be used the sd_* api or not.

And it assumes that when you have the softdevice in flash you should enable the softdevice before using the driver. We are working on adding the checking that the softdevice is present but not enabled.

Regarding your issue with sd_mutex_ could you let me know some more information about that ? I guess you want to look a variable before you printing it out ? I'm not sure there is an equivalent call for mutex when softdevice is disabled.