Clarification on the bluetooth APIs

[eliabieri]

Hello everyone,
I'am exploring the different bluetooth examples at the moment. Maybe I'm the only one but for me the bluetooth documentation seems quite confusing.

As fas as I know we get these different APIs:

• esp_vci API
  esp_ble API
  esp_bt_controller API
  esp_bluedroid API
  and maybe some more

The esp_vci API seems very low level to me and is used in the ble_adv example.
The gatt_server example seems to use a more abstract api.

Maybe someone can clarify the differences between these api and their different use cases.
I'd be willing to update the documentation to make it easier for new users to explore the esp32 bluetooth apis.

[kolban]

While studying BLE, I seem to find that I can get away with:

* esp_ble_gap_*
* esp_ble_gattc_*
* esp_ble_gatts_*

and a couple of black box initialization functions at the start.