Identification of peripheral devices connected to central

[sne_333]

Hello Everyone. 

                       I am a newbie in NRF52840 development. I have one NRF52840 device as a central device and many peripherals are getting connected to it (Max 6). Lets say 6 peripherals are connected to one central. I am not understanding how to identify the different peripheral devices on central side. There is p_gap_evt->conn_handle and &p_gap_evt->params.adv_report.peer_addr but I am not understanding how to use this to identify events from different peripherals??? Can anyone please help me on this? 

[Einar Thorsrud]

Hi,

You are on to it. The key is the connection handle (conn_handle). Any event you get that relates to a specific connection, or any API function that operate on a specific connection, includes this handle. So if you are a central connected to 6 peripherals all will have unique connection handles.

This starts when the connection is established and you get the BLE_GAP_EVT_CONNECTED. With that, you get a conn_handle which has a value. Say that value is 1. Then whenever you get another event where the conn_handle is 1, you know it is for the same peer device (peripheral in this case as you are making a central). If the conn_handle is 2 instead, you know it is for a different connection.

[sne_333]

Thank you Einar. 

so for 1st connection..conn_handle will be 1, 2nd connection conn_handle will be 2 and so on... lets say device 2 acquired conn_handle 2. what if conn_handle 2 disconnects in between?? when device 2 tries to reconnect again, it will acquire new conn_handle or it will connect with conn_handle 2? There is no need to check for peer address??

[Einar Thorsrud]

If it disconnects and connects again it will get a new connection handle. If you need to map it to a specific peer address you can do that by checking the address when it connects, and keep a map of conn_handle and address.

[sne_333]

Thank you so much. Also what is device ID of a peripheral and how is it represented?

[Einar Thorsrud]

What do you mean by device ID? The only IDs you have is the connection handle, which is just a number without meaning, and with the BLE_GAP_EVT_CONNECTED event you get the peer's BLE address.

(There is a concept of device ID in nRF devices, but that is not related to BLE, and is just a random number written into FICR during production in the two DEVICEID registers).