Accessing different services with pc-ble driver

[Kampino]

Hello,

I try to connect a BLE application with my PC by using an nRF52840 dongle and the PC-BLE driver. But I got stuck in the understanding of the driver, so I hope that someone can help me.

The ESP32 provides two additional services: 

• A device information service
• A battery service

I run a modified version of the BLE driver from a Qt application and the service discovery outputs three services

"Received service discovery response. Service count: 3"
" Service UUID: 0x1800"
" Service UUID: 0x1801"
" Service UUID: 0x180a"

But where is the fourth service? I only got the two common services and the device information service, but the battery service is missing.

How can I use multiple services with the BLE driver? I have figured out that I can store the handles of each service by looping through each service after the discovery. And I assume that I have to use each handle to access a discovered service?

And I´m looking for an example for reading / writing some values from the characteristics of a given service. Do you have an example?

Thank you for your help

[Kampino]

Hi Hung Bui ,

yes I have checked it and it helps. But I´m looking for a more generic way to discover all services without letting the application know how many services it should discover. Is there a way to iterate through

sd_ble_gattc_primary_services_discover

until all services are discovered? How can I get feedback that the application doesn´t have discovered all services? I´m missing how I can implement the handling of different services with the pc-ble-driver. Is there an example how to do it?

[Hung Bui]

Hi Daniel, 
As far as I know the application need to call sd_ble_gattc_primary_services_discover() again and again until you receive the BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP event with ATTRIBUTE_NOT_FOUND.

Please have a look at this sequence chart here: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v7.3.0/group___b_l_e___g_a_t_t_c___p_r_i_m___s_r_v_c___d_i_s_c___m_s_c.html?cp=4_7_3_1_2_2_3_10

[Kampino]

Hi Hung Bui 

thanks. I figured it out today after I found the sequence chart. The application is finding all services now, but I have a new problem.

I try to build up a tree view with all the services and all the characteristics. I got all the services already, but I need the characteristics for each service too

I also get the characteristics from "sd_ble_gattc_characteristics_discover". Is there a way to figure out which characteristic is from which service?

[Hung Bui]

I assume you are trying to do is to do generic service discovery. Very similar to what our nRF Connect BLE app is doing. 
I would suggest to have a look at this discussion here: custom service discovery in BLE_Central 

It's about 4 years old but still relevant I think. 

After you receive the services, you would also receive the uuid and the handle_range of the services. Based on the range, you can start doing your characteristic discovery. 

I would suggest to have a look at our ble_db_discovery.c as the reference. 

[Kampino]

Hi Hung Bui 

thank you. I´ve got it now