sd_ble_gatts_hvx() returns NRF_ERROR_INVALID_STATE (error code 8)

[armin]

Hi

Try to send characteristic notification by invoking sd_ble_gatts_hvx() with the following parameters:

	uint32_t err_code = NRF_SUCCESS;
	ble_gatts_hvx_params_t params;

	memset(&params, 0, sizeof(params));
	params.type = BLE_GATT_HVX_NOTIFICATION;
	params.handle = GetValueHandle();
	params.p_data = pData;
	params.offset = 0;
	params.p_len = &length;

	if (srv::ble::ConnectionHandleInvalid != mrBleInterface.GetConnectionHandle())
	{
		err_code = sd_ble_gatts_hvx(mrBleInterface.GetConnectionHandle(), &params);
		assert(err_code == NRF_SUCCESS);
	}

Unfortunately, the error code 8 NRF_ERROR_INVALID_STATE occurs. The connection is established and bonding is completed. ( checked by the DM_EVT_LINK_SECURED event from the device manager)

Do you have any suggestion what "invalid state" coulde be?

Thanks for your help.

BR Armin

[Pål Håland]

The most likely scenario is that the CCCD has not been enabled by the peer device. This has to be enabled before you are able to transmit notification/indications. The peer would have to subscribe to the characteristic to get notifications from it.

Another reason is if you receive an invalid connection handle from mrBleInterface.GetConnectionHandle()

[armin]

Thanks, the connectionHandle has the value 0! ..guess it's correct, sinde the value is set when receiving the ble stack callback event BLE_GAP_EVT_CONNECTED. I will check the CCCD enabling by the peer device (android).

[armin]

Hi Tried to catch the BLE_GATTS_EVT_HVC event when the android sends the BluetoothGatt: writeDescriptor() - uuid: 00002902-0000-1000-8000-00805f9b34fb belonging to the charactersitic.

I suppose the BLE_GATTS_EVT_HVC is sent by the registered callback of softdevice_ble_evt_handler_set(). I lookup in the "ble_event*" p_ble_evt->header.evt_id but did not receive anything, although android confirmed the proper execution..

Any idea about the problem? Thanks, Armin

[Pål Håland]

Hi armin, when the peer device write to your database you will receive a BLE_GATTS_EVT_WRITE and not HVC. There might be more CCCD's in the database as well, like the Service Changed, or for other characteristics. If you have more NRF51 devices, you can try to use the NRF Sniffer to sniff the over the air transaction as well.

[armin]

Hi Pal ..and how do I distinguish between updated CCCD register's and normal Gatts data write?? e.g. android writes CCCD enable or data to characteristic? And what does this API description mean??

"An indication on the other hand will use the standard server internal buffer and thus will only generate a BLE_GATTS_EVT_HVC event as soon as the confirmation has been received from the peer."

developer.nordicsemi.com/.../a01056.html