nRF51 UAart Example data loss over bluetooth interface

[GlennEngel]

In looking at the nRF51 UART Example I'm wondering about data loss over the Bluetooth interface.

When bytes are sent to the host, is there a re-transmission mechanism somewhere that insures the bytes actually reach the host? I understand why flow control is needed on the actual UART hardware but what insures that the data actually makes it over the wireless connection without loss? Is there a way for the client to know if it needs to resend some of it's queued data or is the example just send and hope for the best?

[Kenneth]

Hi, all packets transmitted over a BLE link will be retried infinitely until link loss, all packets are protected by a CRC on the link layer. This is fully handled by the softdevice.

However on link loss (BLE_GAP_EVT_DISCONNECTED event) the last packet(s) that was in process of being sent might be lost. The application can on next connection establishment (BLE_GAP_EVT_CONNECTED event) do some handshaking on application layer to inquire where data should proceed.

[Kenneth]

On link loss the softdevice will provide a BLE_GAP_EVT_DISCONNECTED event to the application. How you want to handle this is entirely up to the application.