Speed up DB Discovery

[RPDben]

Hi,

I have a device in the central role that connects to a device with a specific name. I then do a db_discovery_start to get the handles of two of the characteristics. However, it takes a while for the BLE_DB_DISCOVERY_COMPLETE to be triggered (approx 750 - 1000ms). Is there anyway I can speed this up, or get rid of db_discovery altogether? Some additional points:

• I know the UUID of the characteristics
• I know the properties of the characteristic
• I will only ever connect to a device with these characteristics (if I do connect to a device without these characteristics I am happy for an error to be thrown and a reset triggered)

I am using:

• nRF52832
• S132 v4.0.2
• SDK13

My current ble_db_discovery_evt_handler() code is below:

static void ble_db_discovery_evt_handler(ble_db_discovery_evt_t *p_evt)
{
	ble_gatt_db_char_t * p_chars = p_evt->params.discovered_db.charateristics;
	uint8_t second_handle;
	if(p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE)
	{
		if(p_evt->params.discovered_db.srv_uuid.uuid == BLE_UNIQUE_SERVICE_UUID)
		{
			NRF_LOG_INFO("Found Service \r\n");
			for (uint32_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
			{
				switch(p_chars[i].characteristic.uuid.uuid)
				{
					case FIRST_CHARACTERISTC_UUID:
						first_handle = p_chars[i].characteristic.handle_value;
					break;
					case SECOND_CHARACTERISTC_UUID:
						second_handle = p_chars[i].characteristic.handle_value;
					break;
					default:
					break;
						
				}
			}
			sd_ble_gattc_read(p_evt->conn_handle, second_handle, 0);
		}
	}
	else
	{
		ble_db_discovery_start(&m_ble_db_discovery[p_evt->conn_handle], p_evt->conn_handle);
		NRF_LOG_WARNING("No DB Discovered: %d \r\n", p_evt->evt_type);
	}
}

Thanks in advance,

[Andrzej Kuros]

You can set connection timing parameters to small values (smallest compilant with BLE spec), do db discovery, and then go back to your desired timing.

You can also give up with SDK's db discovery module and do discovery on your own by directly calling SoftDevice's API functions. See sd_ble_gattc_descriptors_discover and related diagrams. It won't be as easy as using db discovery module, but as you know UUIDs it can be faster.