FATAL ERROR using NVS for writing to flash while BLE is active

[V.Lorz]

Hi All,

I'm updating some configuration parameters, which I store in flash using the NVS API, inside the callback that handles a characteristic write. So, flash writes occur while BLE is active.

Whenever I write to flash using nvd_write() a FATAL ERROR exception is raised.

I came across this recent post here, which provides a concise reasoning about causes, and suggests that Zephyr's NVS drivers are the recommended approach and state that: "Zephyr modules such as NVS will do the same when writing or erasing flash while BLE is enabled, but then through the APIs implemented in soc_flash_nrf.c". "The same" here presumably refers to "to use async APIs", to my best understanding.

But thing is I'm using the NVS APIs and that FATAL ERROR comes up every time I try to write to flash. If I do it before starting BLE it all works like a charm.

Questions are: How do I solve this situation, so I can store structured data in flash without requiring to bring BLE down, then write to flash, then bring it back up again?

NVS is very convenient and releases me from needing to implement a file-system or alike.l

BR,

[Sigurd Hellesvik]

Do you by chance write to NVS from a BLE callback?

If not, can you explain a bit on how you test writing to NVS while BLE is on?

Regards,
Sigurd Hellesvik

[V.Lorz]

Hi,

Yes, I do, I write to NVS "inside the callback that handles a characteristic write."

The test I mentioned that works OK is writing/reading before initializing BLE.

BR

[Sigurd Hellesvik]

I recommend not calling NVS functions from a callback.

Instead, either do it the easy way and set a global variable that you poll in a thread somewhere.
Or, do it the more clean way and use a work queue which you trigger from the callback.

[V.Lorz]

One thing to note here is the callback function is not called from inside an ISR context, but from a work thread. Zephyr does that for us, which is nice and convenient.

Of course I can enqueue the job for later, but I can still face the same issue at random because the origin is BLE has very tight timing requirements, so flash operations MUST be executed synchronized with its operation.

Question remains the same: How can I achieve that?

[Sigurd Hellesvik]

Aha, yea no then it should not matter that it is called from a callback I think.

The NVS drivers use the flash API, which is defined for nrf here.

V.Lorz said:

BLE has very tight timing requirements, so flash operations MUST be executed synchronized with its operation.

You are right, and this is already taken into account in our SDK, as long as CONFIG_SOC_FLASH_NRF_RADIO_SYNC_NONE is not set. You can see how this is handled in the flash write driver.

Can you check this option for your project?