NUS UART Service - Getting confirmation after writing to the gatt queue?

[Ros]

Hi,

I am new to the SoftDevice and I am using NUS UART example (nRF5_SDK_16.0.0_98a08e2\examples\ble_central\ble_app_uart_c\pca10040\s132\ses). In server side, after writing to the gatt characteristic (ble_nus_c_string_send), how can confirm that the other device read the data? I am not sure the example uses indication or notification.

Thanks

Ras

[Amanda Hsieh]

Hi, 

In server side, after writing to the gatt characteristic (ble_nus_c_string_send), how can confirm that the other device read the data?

Not sure I understand the question correctly or not. Please correct me if I am wrong. 

The Server cannot write to the Client. When the client sends a write request to the server, the server would send Confirmation. 

Please see the following figure for data transfer:  

 

I am not sure the example uses indication or notification.

 It uses notifications.  Please see Nordic UART Service Client. 

-Amanda H.

[Ros]

Hi,

Sorry for the confusion, the question was how to implement an indication instead of sending notification (I mean after server writing or updating its own characteristic). Where would I receive an "indication confirm event" in the peripheral (server) ?

[Amanda Hsieh]

Hi, 

The idea behind the indication is that has to be confirmed by the application, the SoftDevice won't do it for you.

To do so you have to call the sd_ble_gattc_hv_confirm(..) function, after receiving the BLE_GATTC_EVT_HVX event.

The main purpose of indications is to allow the application to confirm the packet only after it has fully processed the data, and completed any operations associated with it.
If quick and efficient data transfer is more important I would recommend using notifications instead, you still have a link layer ACK to avoid packet loss/corruption.

-Amanda H.