Android: Read characteristic without service discovery

[PVS]

We are writing an Android app for our own peripheral (nRF51-based). We know the handles for all the characteristics.

On Android gatt.discoverServices() needs to be called, and wait for onServicesDiscovered(), then getServices(), before the Characteristic object is available.

This is very time-consuming, and often onServicesDiscovered() does not get called (despite connection success).

Is there a way to directly to write to an attribute handle or a characteristic UUID, bypassing all the discovery steps?

[Hung Bui]

No, as far as I know.

How often do you have the issue "often onServicesDiscovered() does not get called" ? Do you see that when you use our nRFConnect app ?

[Aleksander Nowakowski]

Hi, all the BLE-related method calls are listed on the Log in nRF Connect on DEBUG level. Also, I write there delays (e.g wait(600)). nRF Connect waits for 600ms after it gets connected before calling discoverServices(). Also, (IMPORTANT) if you have nRF Connect in the background (left with HOME button, or switched to another app without exiting the nRF app with a Back button), and there was the GATT server enabled (any configuration,even empty has been selected), and Settings->Connectivity->Show incoming connection is enabled (default), the nRF Connect (or any other app with GATT Server running) will "intercept" your connection on Android pre-7.0. It has been fixed in 7.0. Before, the connection could had only 1 listener for service discovery, so if you call serviceDiscovery(), then nRF calls it again, only nRF gets callback.