sd_ble_gatts_hvx vs. ble_nus_data_send

[DL_November]

As I'm new to the BLE, I'm trying to make use of examples enclosed in the nRF5 SDK.

Now, I found that there exist several functions that seem like do similar things and they make me confusing...

Is there any difference between sd_ble_gatts_hvx() and ble_nus_data_send()?

I think the former gets input as ble_gatts_hvx_params_t struct and the latter gets ble_nus_t struct and some more.

If they do the same thing, data transmission via Bluetooth, then why there are two functions with different types of input?

[Hung Bui]

Hi DL,

Have you looked inside the code of ble_nus_data_send() ? At the end of the function it calls sd_ble_gatts_hvx(). So the purpose is the same, ble_nus_data_send() is just the implementation in the service to prepare and call sd_ble_gatts_hvx()

[DL_November]

Hung Bui said:

Have you looked inside the code of ble_nus_data_send()

Oh, I missed it. I just looked infocenter to figure out what it does...

Then, if I manually implement preparing steps, there will be no difference to just using sd_ble_gatts_hvx(), right?

[Hung Bui]

No, sd_ble_gatts_hvs() is the SVC function provided by softdevice. Any application implementation that want to send notification would need to use that same function. 

[DL_November]

So... sd_ble_gatts_hvs() is the SVC function which is used for nRF SoftDevice. And, ble_nus_data_send() is the service function in application layer?

Is there any delay or cost for calling sd_ble_gatts_hvs() directly in main.c?

[DL_November]

I'd rather try and figure out which one is better...

Thank you Hung Bui for the answers!