how to discover ble services at connected ble peripheral without adding services to softdevice

[nikunj8086]

hi,

i am doing a project where i am using a pca10040 board as central device and a another pca10040 board as peripheral device.

i am able to connect peripheral device using device address and found available primary or secondary services on connected device using "find_adv_uuid()" from "ble_app_hrs_c" example of sdk 14.2.  now if peripheral device has custom service (128-bit uuid) or both custom services and primary services i will only get 128bit base uuid. now how to find available services on connected node and start receiving notification.

thanks.

[Håkon Alseth]

Hi,

 

When you connect to a peripheral, you do a service discovery, which provides you the whole list of available services and characteristics.

If a peripheral has any CCCDs (client characteristic configuration descriptor), then it means that the peripheral supports notification/indication, meaning that it can send data to the central once permissions for this is granted. Please see our tutorials for more information: https://devzone.nordicsemi.com/tutorials/, more specifically this section: https://devzone.nordicsemi.com/tutorials/b/bluetooth-low-energy

 

Best regards,

Håkon

[nikunj8086]

hi, Håkon Alseth

thanks for your response,

actually i am trying to replicate nrf connect mobile app in ble centeal device so that my central device can discoer all the services available in peripheral device.

so i did service discovery in sdk14.2.0  ble_app_uart_c example.and ble_app_hrs_c example.

so first in ble_app_hrs_c example i have put a break-point at "BLE_HRS_C_EVT_DISCOVERY_COMPLETE"

and in "m_db_disc" i am able to see only heart rate service (0x180d) and battery service(0x180f) but not device info service (0x180A) and other flags with in m_db_disc like discovery in progrss is true and discovery pendi is false.

in second ble_app_uart_c i have used for costom service dscovery.

so i added costom base uuid of nordic thingy 52 and started service discovery again i only recived forst service 0x0100 not any other service.

please let me know where i am getting wrong.

thanks

[nikunj8086]

Håkon Alseth said:

Please see our tutorials for more information: https://devzone.nordicsemi.com/tutorials/, more specifically this section: https://devzone.nordicsemi.com/tutorials/b/bluetooth-low-energy

in this tutorial it says that i have to use event register using 

return ble_db_discovery_evt_register(&uart_uuid, db_discover_evt_handler);

but in my case i don't know which service uuid is available on ble peripheral.

and i want to find list of available services on ble peripheral.

[Håkon Alseth]

Hi,

 

This is the softdevice API call to discover primary services on a peripheral:

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v5.0.0/group___b_l_e___g_a_t_t_c___f_u_n_c_t_i_o_n_s.html?cp=2_3_1_1_0_2_2_2_8#gaa778ccc1990e05fffa4aaf304c95e614

 

In order to discover all services (even unmapped UUIDs), you need to provide p_srvc_uuid  = NULL, If you are discovering unmapped 128 bit UUIDs, there is a note:

If any of the discovered services have 128-bit UUIDs which are not present in the table provided to ble_vs_uuids_assign, a UUID structure with type BLE_UUID_TYPE_UNKNOWN will be received in the corresponding event.

The problem is that the db_discovery library does not allow you to pass NULL as the p_srvc_uuid, so you will have to create your own library/logic for discovering all services on a device.

You can discover all standardized 16-bit UUID services, like battery service, device information service, and other services listed here on bluetooth.org:

https://www.bluetooth.com/specifications/gatt/services

 

You can use nrf connect for the PC platform to do this instead of creating a specific firmware that does generic service discovery on any bluetooth LE device.

Is there a specific reason why you want to perform generic service discovery of any device on your central? Normally you want to connect to a peripheral that supports your services.

 

Best regards,

Håkon

[nikunj8086]

Håkon Alseth said:

Is there a specific reason why you want to perform generic service discovery of any device on your central? Normally you want to connect to a peripheral that supports your services.

actually i don't know my self it's my costumer's requirement

but any way thanks for your response it was really helpful to me.