(BLE advertising) nRF automatically connect to my phone and prevent it from other device

[Pham Tam]

Hi, 
I'm build an application that my nRF advertising and my phone (I can call it is phone A), and my friend's phone (phone B)
1.  phone A and phone B can connect automaticially to nRF when nRF start advertising and phone A and B turn on Bluetooth.

2. When another phone (phone C, D...) tries to connect nRF. my nRF will prevent connection from them. They must be added by my nRF like phone A and phone B were added before (I think "whitelist" but I'm not sure about this, I'm new to this)

=> So how can I set up automatic connection and add another device (phone C, phone D) with the same function as phone A, phone B.
Thank you so much !

[Hung Bui]

Hi Tam, 

The most common way of adding such feature as you described is to use a whitelist. 

When a device advertises in whitelist, it won't allow the connect request from the centrals that are outside of the whitelist. 

So in your case if A and B is in the whitelist but not C and D then it would work exactly as you described. 

Some of our examples (e.g ble_app_ancs_c, mouse, keyboard etc ) supporta whitelist by default. A device is automatically added to whitelist after it's bonded. 

However, the difference here is that we defined a button (BSP_EVENT_WHITELIST_OFF) to turn off the whitelist. So if you want to add a new device to the whitelist, you need to press the button to allow "normal" advertising. This will make it possible for C and D to connect and join the whitelist. 

We currently don't have the code to allow adding C and D via A and B. You would need to make your own mechanism to send the data about C and D from A/B down to the node and update the whitelist. The advertising module has an event that request the application to provide the whitelist , have a look here and please refer to the examples I mentioned above. 
Your task is to find a way to send either address of C/D or their IRK to the node to update to the whitelist.