sd_ble_gattc_char_value_by_uuid_read - again

[Martin]

Hi

I'm fighting to read characteristics of my service with sd_ble_gattc_char_value_by_uuid_read. I'm using SD130 V2.0.1 and SDK11.

Here are some snippets from my central device. I register my custom 128bit UUID in the SD130 like so:

err_code = sd_ble_uuid_vs_add(&m_svc_uuid, &m_uuid_type);
APP_ERROR_CHECK(err_code);

m_uuid.type = m_uuid_type;
m_uuid.uuid = MH_BLE_UUID_SERVICE;

then the normal scan and connect takes place. In the ble connect handler I call:

	m_range.start_handle = 0x0001; // CHAR Start on create: 0x1101
	m_range.end_handle = 0xffff; // CHAR END on create: 0x1105
	err_code = sd_ble_gattc_char_value_by_uuid_read(p_gap_evt->conn_handle, &m_uuid_type, &m_range);

No matter if I add the known characteristic handles or the full range, the error is the same. The function call executes with NRF_SUCCESS, but in the BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event handler, the returned status is always BLE_GATT_STATUS_ATTERR_ATTRIBUTE_NOT_FOUND 0x010A.

Am I missing something or is my call in the wrong place? It would be great if somebody could supply a more detailed explanation then the one in the docs. I couldn't find any example using the call on devzone or in SDK exmples....

Thanks

[endnode]

Some code samples are here (and probably more instances on this forum). My feeling is that your problem is simply in UUID you are providing to the call (like little vs. big endian or similar mistake;)

[Martin]

Yes, this is what I suspect also, but it is puzzling me that db_discovery module is working fine with it and is discovering stuff... I followed all hints I found - but nothing solved this

[endnode]

So then use Nordic sniffer or similar device to see what is actually done over radio so you can be sure if your service was even listed in ATT/GATT request/response exchange...

[Hung Bui]

Hi Martin Petter,

Please be noted that in the call sd_ble_gattc_char_value_by_uuid_read() the parameter *p_uuid should be the UUID of the characteristic, not the m_uuid_type. The m_uuid_type is the ID of the base UUID in the database. the UUID of the characteristic should consist of uuid_type and the actual UUID (16bit UUID for the characteristic).

For example in our UART service, the base UUID is

NUS_BASE_UUID                   {{0x9E, 0xCA, 0xDC, 0x24, 0x0E, 0xE5, 0xA9, 0xE0, 0x93, 0xF3, 0xA3, 0xB5, 0x00, 0x00, 0x40, 0x6E}}

But the 16 bit UUID for RX characteristic, for example, is

#define BLE_UUID_NUS_TX_CHARACTERISTIC  0x0003 

And it's the charactersitic's UUID, not the service's UUID.

If you still have trouble, please post your code.

[Martin]

Thanks, this very minute I figured it out myself. Looking at it this makes complete sense...