Service Changed Characteristic not enabled on iOS

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Thu, 22 Aug 2019 07:22:28 GMT

Hi Vidar,

adding the service_changed_cccd and modifying the send_in_evt function solved it. Thanks.

/ Anton

RE: Service Changed Characteristic not enabled on iOS

Vidar Berg — Thu, 22 Aug 2019 06:03:27 GMT

No problem. Just let me know if it's not working.

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Wed, 21 Aug 2019 08:56:39 GMT

I see, I was a bit unsure about that part. Thanks for clarifying!

RE: Service Changed Characteristic not enabled on iOS

Vidar Berg — Wed, 21 Aug 2019 08:55:03 GMT

That is correct, the function was added in SDK 15.3.0 and is used to check whether the SC indication is enabled or if it even exists. You need to add this function in the NRF_ERROR_INVALID_STATE case to determine if is "invalid state" because of an ongoing MTU exchange or simply because the indication is not enabled.

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Wed, 21 Aug 2019 08:44:50 GMT

Hi Vidar,

I checked the source files for SDK v15.0 (gatt_cache_manager.c) and I cannot find the function service_changed_cccd function that you mention in the other thread.

RE: Service Changed Characteristic not enabled on iOS

Vidar Berg — Wed, 21 Aug 2019 08:31:09 GMT

I think the changes shown in the *.diff file from my last comment will be valid for v15.0.0 as well. But haven't verified it here.

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Tue, 20 Aug 2019 12:38:43 GMT

Yes SDK V15.0, is the fix you suggested in the other question valid for SDK v15.0?

I have checked and service_changed_cccd function does not exist in SDK v15.0

RE: Service Changed Characteristic not enabled on iOS

Vidar Berg — Tue, 20 Aug 2019 12:38:23 GMT

[quote user="AntonHellbe"]When you say PM API to manage SC indications, do you mean pm_local_database_has_changed()?[/quote]

Yes, that's what I meant. But you need to fix the implementation as I proposed in the other thread to ensure SC indications aren't dropped. Are you on an older SDK version?

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Tue, 20 Aug 2019 12:09:10 GMT

Hi Vidar,

It seems like that the case, I moved the call sd_ble_gatts_service_changed from the event BLE_GAP_EVT_CONN_SEC_UPDATE to BLE_GAP_EVT_CONN_PARAM_UPDATE which comes after roughly 20 seconds after connection. Then it works without issues.

Any advice how to handle this? Putting the call in BLE_GAP_EVT_CONN_PARAM_UPDATE seems abit strange.

Edit:

You can use the PM API to manage SC indications to bonded peers.

When you say PM API to manage SC indications, do you mean pm_local_database_has_changed()?

Also I'm using SDK v15.0

RE: Service Changed Characteristic not enabled on iOS

Vidar Berg — Tue, 20 Aug 2019 11:30:49 GMT

You may get INVALID_STATE if you try to issue a SC indication while there is an ongoing MTU exchange. Could this maybe explain why it's not sent in your case? You can try to send the indication at a later time and see if you still get the error to confirm this.

My iPhone 7 w iOS 12.4 enables SC indication after the bond is established.

Edit: this thread may be relevant as well: https://devzone.nordicsemi.com/f/nordic-q-a/46633/peer-manager-silently-drop-service-changed-indications-if-an-att-mtu-exchange-was-happening/204968#204968. You can use the PM API to manage SC indications to bonded peers.

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Tue, 20 Aug 2019 08:36:33 GMT

Further investigation shows that it happens regardless of reset or not.

I pair / bond using my iPhone 6s running iOS 12.4, after pairing/bonding is complete my application running on the nRF52832 sends one notification successfully. Then the iPhone gets disconnected regardless, when I reconnect I receive NRF_ERROR_INVALID_STATE when trying to send Service Changed notifications

RE: Service Changed Characteristic not enabled on iOS

AntonHellbe — Tue, 20 Aug 2019 08:20:20 GMT

Hi,

I think I have found the issue. After pairing/bonding another CPU resets the nRF52832, but before that happens I can see that the application can send one notification. When the nRF52832 boots up again and I reconnect I receive error NRF_ERROR_INVALID_STATE. It seems like the CCCDs are not saved on Central side it seems like.