Advertised characteristics do not update on iOS NRFConnect 2.3.2

RE: Advertised characteristics do not update on iOS NRFConnect 2.3.2

Vidar Berg — Mon, 24 Aug 2020 13:30:47 GMT

[quote user="daubsi"]I had partly success. On the one hand when building a new project from scratch using the template project it did not occur so far that I saw "old" characteristics that look like remainder from previous projects in the nRFConnect tool despite the project does not even include those characteristics. As such I cannot say if NRF_SDH_BLE_SERVICE_CHANGED would actually help here.[/quote]

It's important that the cache is cleared before you add NRF_SDH_BLE_SERVICE_CHANGED, else it will not have any effect (iOS will not know that it has been added).

[quote user="daubsi"]iOS in general due to the different BLE implementation layer in the OS. I hope a later update can remedy most of the problems.[/quote]

It should feel fairly responsive. I just tested this on an iPhone 8 with nRF connect version v2.3.2 and it took one press and approx. 1 second to enable notifications on the hrs characteristic. This is with a relatively slow connection interval (400-500ms). You may try to reduce the connection interval to see if that helps (iOS will accept 15 ms intervals if you request MIN_CONN_INTERVAL=MAX_CONN_INTERVAL=15ms).

RE: Advertised characteristics do not update on iOS NRFConnect 2.3.2

daubsi — Sun, 23 Aug 2020 18:32:36 GMT

I had partly success. On the one hand when building a new project from scratch using the template project it did not occur so far that I saw "old" characteristics that look like remainder from previous projects in the nRFConnect tool despite the project does not even include those characteristics. As such I cannot say if NRF_SDH_BLE_SERVICE_CHANGED would actually help here.

I also have an old Android tablet running Android v5.1.1 and what I can say in direct comparison is that the Android variant of nRFconnect seems to be much more responsive and stable than the iOS pendant. In the Android app I can tab on a characteristic and the desired action is executed immediately. In the iOS it constanly seems as if the app is hanging or frozen, like the Read/Write icons change state but don't reactivate or seem to do any action. I need to tap 3 or 4 times on "Notify" until the request is finally received at the DK etc. I can confirm that it is not an issue with my code as it works perfectly and reactive using nRFconnect for Android. As I am a beginner with nRF tools and products I cannot say if it is this particular version of the nRFConnect tool which is buggy or whether it is a problem on iOS in general due to the different BLE implementation layer in the OS. I hope a later update can remedy most of the problems. Other tools like LightBlue seem to be more responsive to user interaction here as well.

RE: Advertised characteristics do not update on iOS NRFConnect 2.3.2

Vidar Berg — Wed, 19 Aug 2020 12:15:56 GMT

Hello,

The iPhone is likely doing what's known as attributes caching. It's a BT feature that allows it to skip service discovery every time it connects to your device. For a complete summary of this feature I recommend you take a look at the following section in the Bluetooth core spec: vol3, part g, section 2.5.2. Anyway, in order to clear the cache and force a new service discovery, first, make sure it's not in the list of bonded devices in settings->bluetooth, then toggle flight mode enable (or reboot the phone). The cache should be cleared after this.

You may also consider building the app with NRF_SDH_BLE_SERVICE_CHANGED enabled. This adds the service changed characteristic to the attribute table, which effectively disables attribute caching for non-secure connections.