nrf connect app problem

Question

Dear friend，

I am doing a test like this: 1. Connect the Bluetooth device with the nrf conncet app of the Android phone. 2. The notify (CCCD) is enabled. 3. Click "disconnect" on the nrf connect APP to disconnect. 4. Click "connect" again to reconnect. Result: I see that the notification of nrf connect app is still in the enabled state (in fact, the notification of the Bluetooth terminal is in the disabled state). And repeat the above steps 1-4 with the nrf connect app of the ios phone, there is no such phenomenon. The operation video of the nrf connect app on Android phones is as follows: 
 Why is the nrf connect app phenomenon of Android phones and ios phones different? What is the difference between them? Is nrf connect app a normal phenomenon?

Aleksander Nowakowski · Accepted Answer

Hello, 
 This is not a "phenomenon". Your device is bonded, which means both client and server can store the value of Client Characteristic Configuration Descriptor (CCCD), so that after reconnection enabling notifications/indications is not required. nRF Connect for Android does it. It cannot verify whether the other side in fact also has stored CCCD value (without reading CCCD value), but with Nordic SDKs it should be true. You may always read the value of CCCD to update the value. 
 Had your device not been bonded, you would not have had this "phenomenon". 
 Also, another fun fact, if nRF Connect receives a notification/indication from a characteristic which had the value set to "disabled", is assumes they were actually enabled, and changes the CCCD state accordingly. For that, nRF Connect calls setCharacteristicNotification with value true for each characteristic with NOTIFY/INDICATE properties (you can see it in the log). This does not enable notifications remotely, but notifies Android system, that the local client is interested in receiving updates on those attributes.

nrf connect app problem

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