Update advertisement manufacturer data once per second

RE: Update advertisement manufacturer data once per second

Bragma — Mon, 03 Dec 2018 13:27:49 GMT

AmbystomaLabs I followed your suggestion, I've used an app timer to simulate an external source and update the data and everything seems well. Thank you all!

RE: Update advertisement manufacturer data once per second

AmbystomaLabs — Sun, 02 Dec 2018 16:10:01 GMT

You don't need to synchronize with the radio to update the manufacturer data. Just change the data in the packet structure and re-init advertisements. The softdevice won't crash, it will just use the new data on the next advertisement.

We do precisely this for one of our products. It works perfectly.

RE: Update advertisement manufacturer data once per second

Bragma — Sun, 02 Dec 2018 14:07:19 GMT

Thanks, I am expecting the 2 events (update <-> send) to be completely async, it's not a problem for my app. The real question is if it may cause crashes or other criticals. If the only problem is that a write is missed, it's not really that important. Data will either be sent on the next advertisement packet or be superseded by new data.

I'm not sure I've explained my use case. Data is produced continuously at a more or less fixed rate (ex: about once per second), while advertisement will either be fast or slow (and have their timings completely unrelated to data). I just want the advertisement to pick up the new data I write with ble_advdata_set. I think I will be using static structures and all data has meaning at byte level. So event if I am writing while advertisement is in progress, it's not problem if data is only partially updated.

The question is if this may cause any crash, because at data level I have not worries.

Thanks!

RE: Update advertisement manufacturer data once per second

natersoz — Sat, 01 Dec 2018 19:20:18 GMT

The problem will be that your calls to set the manufacturer specific ID will likely be asynchronous with the BLE timer which performs calls to send out the advertising packets.

As simple solution would be to wrap your setting of the manufacturer ID with the app_util_critical_region_enter() and app_util_critical_region_exit() functions. Their function definitions are in the SDK 15.2 directory nRF5_SDK_15.2.0_9412b96/components/libraries/util/app_util_platform.c and associated .h file.

This will prevent the BLE timer interrupt from reading the manufacturing data from the advertising structure before you are done writing to it.