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

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

nikunj8086 — Tue, 17 Apr 2018 07:05:06 GMT

hi Håkon Alseth,

i have 2 question that,

1. now i want to know what is data length sent by ble peripheral service characteristic which has only notification attribute, without enabling notification.

2. how to discover custom characteristics within primary service.

ie. nordic thingy 52 has dfu service 0xFE59 which is a primary service and it's characteristic has secondary type UUID so i am not able to discover it unless i register 128-bit base uuid into softdevice.

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

nikunj8086 — Mon, 26 Mar 2018 07:45:24 GMT

[quote userid="2115" url="~/f/nordic-q-a/31305/how-to-discover-ble-services-at-connected-ble-peripheral-without-adding-services-to-softdevice/124514"]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.[/quote]

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.

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

Håkon Alseth — Thu, 15 Mar 2018 08:37:30 GMT

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

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

nikunj8086 — Wed, 14 Mar 2018 10:02:39 GMT

[quote userid="2115" url="~/f/nordic-q-a/31305/how-to-discover-ble-services-at-connected-ble-peripheral-without-adding-services-to-softdevice/124133"]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[/quote]

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.

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

nikunj8086 — Wed, 14 Mar 2018 06:13:20 GMT

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

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

Håkon Alseth — Tue, 13 Mar 2018 11:00:56 GMT

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