Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

erickcinco — Thu, 14 Jan 2021 15:35:48 GMT

Turns out I handle the BLE_GAP_EVT_PHY_UPDATE_REQUEST case in all of my embedded applications except for this one!

Note that this also works with iOS if you want to use PHY2MBPS.

case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
    
    NRF_LOG_DEBUG("PHY update request.");
    ble_gap_phys_t const phys =
    {
        .rx_phys = BLE_GAP_PHY_2MBPS,
        .tx_phys = BLE_GAP_PHY_2MBPS, 
    };
    err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
    APP_ERROR_CHECK(err_code);

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

DDelforge — Thu, 14 Jan 2021 10:51:43 GMT

Hi, thanks for your feedback,

Indeed with little change, it's now working perfectly on my iOS devices !

Thanks a lot !

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

Susheel Nuguru — Thu, 14 Jan 2021 10:19:05 GMT

Sorry for the late reply.

It looks like the issue is that your BLE device is not responding to LL_PHY_REQ which some IOS centrals are querrying for.

Can you please add a response to that request as below in your ble_event_handler in you app

        case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
        {
            NRF_LOG_DEBUG("PHY update request.");
            ble_gap_phys_t const phys =
            {
                .rx_phys = BLE_GAP_PHY_AUTO,
                .tx_phys = BLE_GAP_PHY_AUTO,
            };
            err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
            APP_ERROR_CHECK(err_code);
        } br

and see if that works.

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

erickcinco — Tue, 12 Jan 2021 17:47:33 GMT

I am seeing the same behavior.

With my peripheral embedded device under the debugger I can see a connection request go through and the connection seems to be properly established (from the peripheral's perspective). I have not seen any issues on an Android device. Curiously, the iPhone SE (1st Gen) works with both iOS 13 and 14.

DDelforge's capture shows that the central app and peripheral device establish a connection and keep the connection alive with Empty PDU packets.

Could it be that the iOS apps are not handling a connection event correctly which leaves it stuck in the "connecting" state?

iPhone 7 - iOS 13.5.1
iPhone SE (1st Gen) - iOS 13.5.1
iPhone SE (1st Gen) - iOS 14.3
iPhone 11 ProMax - iOS 14.0.1
iPhone 11 - iOS 14.3
iPad Air (4th Gen) - iOS 14.3
Samsung Galaxy Note 20 - Android
LG Nexus 5X - Android 8.1.0

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

DDelforge — Tue, 12 Jan 2021 12:55:09 GMT

Hi,

You can find some logs generate et tested with the original code from Nordic (ble_thread_dyn_mtd_coap_cli) and nrfConnect. Chip used is nrf52840.

Inside the .zip file, you will find logs from successful connection, but also logs where connection fails.

devzone.nordicsemi.com/.../Wireshark.zip

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

Susheel Nuguru — Mon, 11 Jan 2021 12:36:03 GMT

Then somehow you need to provide me the sniffer log of the failed connection transaction.

If you have an extra nRF kit, then you can use it as a BLE sniffer using the firmware given here and using Wireshark. I am not sure how else to see what went wrong with the connection.

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

DDelforge — Mon, 11 Jan 2021 10:40:12 GMT

Hi,

Thanks for the input. I tried the proposed solution, unfortunately i got the exact same issue.

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

Susheel Nuguru — Mon, 11 Jan 2021 10:16:08 GMT

Hi,

I asked the IOS expert to see if he knows about some issue regarding IOS incompatibilities with any BLE versions. It seems that this is something new to us.

We suspect that this might something to do with IOS BLE caching mechanism which is not updated with your device info.

Can you please try to do this for the failing device

close the nRF Connect App.
Go to settings and turn off Bleutooth. You need to turn of the Bluetooth from the main IOS settings and not from the control center.
turn the bluetoon on again and
start the nRF connect app and try to connect again.

This should forcefully update the BLE cache and nRF Connect should be able to connect to your device from here on. Please give it a try

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

DDelforge — Mon, 11 Jan 2021 09:26:59 GMT

You are right : using nRF Connect App, I try to connect a nRF BLE Device (this BLE device is a nfr52840 in my case) using my iPhone.

Connection works well on android device (BLE 4 or BLE 5 Compatible devices)
Connection works as well on some iOS devices, but it seems, that some devices running iOS 14 cannot connect my BLE device.

Regarding logs, unfortunately, I don't have much. it seems we are stuck at the step CentralManager.connect(), with failing device, we will never go further than this step.

RE: Cannot connect to nRF52840 from iPhone/iPad running iOS 14 using nRF Connect App

Susheel Nuguru — Mon, 11 Jan 2021 09:05:05 GMT

Just to be clear, you are using nRF connect APP to connect to nRF BLE devices? So nRF Connect app has issues connecting to nRF on some IOS versions?

Maybe a sniffer log from one of the connection failure might help me undestand the problem a bit more in detail.