iOS/iPhone BLE service discovery timeout with ant shared channel demo

[philip]

Hi!

Using the out of the box ANT shared channel demo with a NRF52-DK board and the iOS demo app everything compiles and installs nicely, using the Android-based app nRF Connect for Mobile I can successfully connect and control the hub/peripherals, but the iOS App will not work.

The iOS app will successfully make a connection and start the service discovery with the given service identifier, but this service discovery always times out after +- 30 seconds thus disconnecting the two devices again. Note: 30 seconds is the supervisor timeout in the hub-code, but changing the timeout or deactivating it has no effect. Removing the service filter searching for any services within the iOS app leads to the same result.

Also exactly the same happens using a generic bluetooth explorer app (LightBlue Explorer). Added: The same with the Nordic nrf Connect for iOS

There are no clear BT errors occurring on the device (after adding extra code).

Any plausible app-sided approaches regarding iOS/BLE problems (according SO) did not lead to solutions yet..

Has anyone encountered similiar problems and might have a solution at hand, either app-sided or NRF52-DK-sided?

iPhone 6, iOS 10.2.1 & iOS 10.3.0 (beta) / iPad mini 3, iOS 10.2.0 NRF52-DK (PCA10040, V1.1.1, 2016.48) NRF5 SDK 12.2.0 Softdevice 332, 2.0.1

[Petter Myhre]

I'm not sure what could be causing this. Have you done a sniffer trace to see what is happening on air? You can use the nRF Sniffer. I'll try to test this first thing tomorrow.

[philip]

Ah very good idea, right on it now - many thanks!

[Petter Myhre]

I did a sniffer trace, it seems iOS is sending a ATT MTU request that is not responded to, and because of that iOS disconnects after 30s.

If you replace the ble_evt_dispatch() function with the following, the MTU request should be responded to:

static void ble_evt_dispatch(ble_evt_t * p_ble_evt)
{
    uint32_t err_code;
    
    cntrldevice_event_handler(p_ble_evt);    
    
    if(p_ble_evt->header.evt_id == BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST)
    {
        err_code = sd_ble_gatts_exchange_mtu_reply(p_ble_evt->evt.common_evt.conn_handle, GATT_MTU_SIZE_DEFAULT); 
        APP_ERROR_CHECK(err_code);
    }
}

I would also like to mention that the iOS app is old (2 years), it is not tested with later SDK, and it will not be updated. It can of course still be used as a starting point for development.

[philip]

Super yes, that indeed does the trick - many thanks! I was following the wrong idea.. Just complete: ble_evt_dispatch(..) is to be found in asc_coordinator.c. According to philips77 the new iOS (10.xx) is sending the ATT MTU request which previous versions didn't.