Central: multiple connection at the same time

[Thierry]

Hi,

I'm using S130 with PCA10028 and I would like to connect my central device to multiple peripheral at the same time.

According to my understanding, the only way I have to achieve this goal is to use whitelist. However, once the first device acknowledge my connect, scanning seems to stop and no more connections are done.

Is my understanding correct ? and if yes why ? Where come from this limitation ? (SDK, Bluetooth, hardware...)

Does I have any way to continue connection on other devices without recalling sd_ble_gap_connect again ?

Thanks for your support

[Petter Myhre]

This is just how it is implemented in the SoftDevice, it will connect to the first device found in the whitelist then it will stop scanning. Then you can for example call sd_ble_gap_connect() again when you get the BLE_GAP_EVT_CONNECTED event.

There is no limitation on this, it could have been implemented the way you describe, but it is not. I will add this as a feature request/improvement internally.

[Thierry]

Got it.

Regarding our requirements: typically, user will press a button on central device and the central will have to send a specific command to a list of peripherals (~8).

Of course, this action have to be done as fast as possible and central is not connected to peripherals, so originally I tried to connect to all devices at same time:

for (int i=0; i<8; i++)
    connect(....)

But only 1 connect succeed and others returned INVALID_STATE. So after that I change my algorithm by something like:

connect() //First device
CONNECT_EVENT: //When connect event is received  
    connect() //connect to next device

And this last algorithm worked, however because my goal is to connect as fast as possible, I tried to use whitelist in order to connect to all devices in same time.