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.

[Petter Myhre]

When the central receives an advertising packet from one of the devices in the whitelist, it will send a connection request. Then there are certain timings that needs to be followed when before the peripheral answers. For more information see Vol. 6, Part B, Section 4.5.3 in the Bluetooth Core spec 4.2. The timings depend on the connection interval, but normally you have a short connection interval on initial connection. So the connection should be established quickly compared to the advertising interval of the second device you want to connect to. My point is that it shouldn't be necessary to send another connection request before the previous connection is established.