IOS devices suddenly can no longer connect or discover services

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Mon, 10 Aug 2020 13:08:00 GMT

Yes we can provide you with the required materials to test. I have followed up via email at dinesh.harjani@nordicsemi.no .

RE: IOS devices suddenly can no longer connect or discover services

Dinesh Harjani — Mon, 10 Aug 2020 07:13:11 GMT

Hi Rberanek, nRF Connect app developer here,

If you could provide us with a devkit sample to install and debug this it'd be greatly appreciated.

Nevertheless, I'm happy you and Hung Bui were able to solve the issue 🙂

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Wed, 05 Aug 2020 13:27:36 GMT

LightBlue was able to connect. Looks like this is an BLE library issue on the application side.

Thank you for your help debugging this issue.

RE: IOS devices suddenly can no longer connect or discover services

Hung Bui — Wed, 05 Aug 2020 12:09:15 GMT

I suspect it can be an issue with our nRF Connect app, could you try testing with other app ? For example LightBlue ?

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Tue, 04 Aug 2020 15:14:40 GMT

Yes we have tried with multiple phones. Once the issue occurs it seems all iPhones are not connectable. We have seen the issue on iPhones 6,8,X,11. Restarting the phone did not help. The device remains connectable with android phones.

The iPhones do no have any issues connecting to new devices or other application examples. The issue seems to happen sporadically within a week or two of use.

RE: IOS devices suddenly can no longer connect or discover services

Hung Bui — Tue, 04 Aug 2020 15:04:39 GMT

Hi Rberanek,

From the sniffer trace I don't see any problem with the advertising packet. It's advertise as connectable packet.
I give an example here of a non connectable packet:

You can find the PDU type of 0x02 when in your sniffer trace it's 0x00 meaning it's a normal connectable advertising packet:

Have you tried to use another phone to check if it shows the device as connectable or not ? Please try to restart the phone as well.
In addition, please test with other BLE app, for example Lightblue app .

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Thu, 30 Jul 2020 18:30:16 GMT

I have attached a sniffer log from one of the devices not is not connection to IOS. Same behavior as described previously: device is discoverable, it is connectable with android app and nrf connect, it is not connectable with IOS app or IOS nrfConnect. This device also had a device name corruption issue where the device name is empty. We have seen this correlates with the IOS connectivity issue, but we have also had devices with non-empty device names not connect.

devzone.nordicsemi.com/.../CC27A8F9F70F-IOS-not-connectable-log.pcapng

RE: IOS devices suddenly can no longer connect or discover services

Hung Bui — Fri, 24 Jul 2020 14:30:34 GMT

I think should clarify here. The nRF Connect app display a node as connectable or not connectable only base on the advertising flags.
This should not related to any of the behavior when it's connected or if you support only one peripheral connection.
And this flag should be the same between devices, so when you see it's non-connectable on one phone it should be the same on other phone. It's very strange that you can connect from other phones.

Do you advertise after you have a connection to a central device ? If you do advertise and if you configure to support only one peripheral connection then the softdevice will only allow you to advertise with non-connectable flag.

Please try capture a sniffer trace when you see it's "non-connectable" .

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Fri, 24 Jul 2020 13:01:56 GMT

One idea I have looked at is the the handler for BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST

In gatt_init we run the following:

 err_code = nrf_ble_gatt_att_mtu_periph_set(&m_gatt, NRF_SDH_BLE_GATT_MAX_MTU_SIZE);

However, the handler returns the following:

err_code=sd_ble_gatts_exchange_mtu_reply(p_ble_evt->evt.gatts_evt.conn_handle,23);

Could the mis-matched mtu sizes be causing an issue? I have tried setting handler setting to NRF_SDH_BLE_GATT_MAX_MTU_SIZE as well. So far we haven't had any issues, but we will need to test for at least a few more days to confirm.

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Fri, 24 Jul 2020 12:25:06 GMT

We limit the device to only one peripheral connection. That is the only thing that I can think of that would cause the device to be set to non-connectable.

No we haven't seen any issues with SDK examples, but we haven't tested those in a large deployment. As mentioned earlier this seems to be happening specifically with Iphones X and 11. We have also test on Iphones 8, 6 without issue.

We did scan and connect with an Android phone. The Android phone was able to connect without issue when he had an unconnectable device with an iPhone.

I will follow up once with have a sniffer trace.

RE: IOS devices suddenly can no longer connect or discover services

Hung Bui — Thu, 23 Jul 2020 13:05:51 GMT

From what I can see your device is advertising as non-connectable.
Is there anything in the code that may set the advertising flag to this mode ?
Do you see the same issue with a SDK example ?

Please try to capture a sniffer trace. Also try to use an Android phone to scan&connect, just to cross check.

RE: IOS devices suddenly can no longer connect or discover services

Rberanek — Wed, 22 Jul 2020 17:05:59 GMT

I have attached an image of the advertising scans as well as a successfully connected device. I have tried a few different advertising intervals without any noticeable change in the behavior.

What happened when you try to connect ?

Connection is not available, as you can see the 'Connect' button is grayed out and disabled on nrfConnect. We can't connect via our app either.

Previously we were getting more of these issues when we didn't leave a delay between initializing the fstorage instance and the BLE service. I now have a 500 ms delay between the two which has reduced the frequency of these issues. However adding a delay is not ideal for our application as we need some events the occur right after the device awakes from sleep mode.

I will try and capture a sniffer trace, the issue is sporadic and occurs with some of our beta users so it may take little while before I am able to capture this data.

RE: IOS devices suddenly can no longer connect or discover services

Hung Bui — Wed, 22 Jul 2020 13:50:55 GMT

Hi,

Could you take a screenshot on nRF Connect when scanning for the device that "discoverable but not connectable". What happened when you try to connect ? Could you show the advertising packet detail ?
Please try capture a sniffer trace as well.