What is the difference between IOS peripheral and android peripheral?

[Bibazavr]

I am developing an application for Android and IOS. 

Faced a problem when try connect  nRF Connect as central (on Android) to nRF Connect as peripheral (on IOS)

(screenshot from  nRF Connect as central (Android))

Why is this happening and how can this be solved?

I have the same problem when I try connect nRF52832 as central to IOS peripheral (on Android all works fine)

[Hung Bui]

I'm not sure what the error 160 (0xa0) is about. Could you try capture a sniffer trace when the issue happens ? 
Which error or disconnected reason do you receive on the nRF52 when you used it as the central ? 

[Bibazavr]

A day after the first detection of an error, the next day, trying again - it worked (No errors).

But after an hour of work it again went errors in the console.

I wrote down 2 logs after errors went (before unboundig and after)

I hope they help to figure it out

invalidhandle.pcapng
delete-ios-and-android-bound-error-160.pcapng

P.S.
I tried to remove the pairing on both devices, restart the bluetooth and try to connect again - this did not help. 
 And when trying to connect, Android does not see services on IOS

[Vladislav Kolodiev]

We checked 2 scenarios:
1. connection of the nFR Connect application as central and the application on the iOs with UART service as peripheral . Everything works fine and the iOs application accepts “subscribed” event if has been send event "Notification enabled" from nFR Connect.
2. connection of the application ble_app_uart_c (SDK 15.3) on board PCA10040 and the application on the iOs phone as peripheral. We see that ble_app_uart_c sent "Notification Enable" to peripheral via call ble_nus_c_tx_notif_enable() but iOs app does not received  “subscribed” event. The similar app on Android phone works fine.

[Hung Bui]

Hi, 
Please capture a sniffer trace. It's the best if you can do that with both using nRF Connect application as central and use PCA10040 as the central. 

You just need an extra nRF52 DK to use as the sniffer. 

[Vladislav Kolodiev]

Hi Hung Bui, could you confirm that the app "ble_app_uart_c" on PCA10040 as cental works with nRF Connect on iOs phone as periferal?

[Hung Bui]

Please state how you configure the nRF Connect on iOS as peripheral. How you define the UART service in the app. As far as I know the app doesn't support creating a service in a gatt server. The service you see in the list that you can add to the advertiser is only the list of service for the advertiser.

As I mentioned, please capture a sniffer trace. We can't work without any data. 

[Vladislav Kolodiev]

iPhone.pcapng

I have added file capture of Wireshark. nRF Connect (iPhone) app as peripheral with UART service connects to firmware example ble_app_uart_c (SDK 16.0 and s132_nrf52_7.0.1_softdevice) on board PCA10040 as central.
I am confused why Nordic team cannot perform this test case.

0143.Android.pcapng

This file is Wireshark capture with nRF Connect on an Android phone and ble_app_uart_c.

[Hung Bui]

Hi Vladislav, 

I still don't know how you create the GATT server on the iPhone. Could you please let me know what exactly you did to test that on the phone? 

From the sniffer trace, what I can see is that there is no UART service on the iPhone and the phone refused the write request to enable CCCD from the nRF52. You would need to perform bonding to be able to do that. 

[Bibazavr]

Hi, Hung Bui ,

for IOS app as peripheral i use this https://github.com/randdusing/cordova-plugin-bluetoothle


We record new sniffer trace using app for Android "nRF Connect" as central and my onw app for iOS as peripheral with cordova-plugin-bluetoothle (all works fine)

iphonePeripheralToNRFConnectAndroid.pcapng

[Vladislav Kolodiev]

Hi Hung Bui,  this is log from ble_app_uart_c

BLE UART central example started.
BLE_GAP_EVT_CONNECTED. conn_handle=0
ble_db_discovery_start()
BLE_NUS_C_EVT_DISCOVERY_COMPLETE.conn_handle=0
ble_nus_c_tx_notif_enable(). err_code=0x0
BLE_NUS_C_EVT_DISCONNECTED.
BLE_GAP_EVT_DISCONNECTED. reason=0x13

You can see that UART service is discovered. But iPhone peripheral  does not received  "Notification enable" sending by call ble_nus_c_tx_notif_enable() . It seem as SDK issue because GATT server on the iPnone receive “subscribed” event for UART service if "Notification enable" has been send by nRF Connect app.

[Hung Bui]

So why wouldn't you mentioned about the cordova app earlier ? and you wanted us to test with nRF Connect on iOS ? 

The sniffer trace you provided doesn't show much information as the sniffer couldn't decode the encryption. You would need to sniff the communication before bonding happens. This way the sniffer can catch the trace. 
This also showed that you would need to do bonding before you can read the GATT server on the phone. This is not implemented in the ble_app_uart_c 

You won't be able to write into the CCCD of the server if it require encryption. I'm not sure if you can remove this requirement on iOS. But you can check inside the GATT server by cordova to see if it can have the characteristic without bonding ? 
Otherwise you would need to implement bonding in ble_app_uart_c , please have a look at the ble_app_hrs_c at the call pm_conn_secure() inside hrs_c_evt_handler()

[Vladislav Kolodiev]

Hi Hung Bui, thank you for your help. We were able to find the problem. The iPhone has BT 4.0, but the Andriod has is BT 4.2. And iPnone doesn 't support LESC.