Characteristic Location on notification

[leo]

Hi everyone,

i have an Characteristic with attr_md.vloc = BLE_GATTS_VLOC_STACK;. Is it possible, when i send a notifcation to use params.p_dataand params.len to send data from a different location?

Thanks in advance, Cheers!

[Petter Myhre]

What do you mean by different location? Please clarify by editing the question.

[FormerMember]

When transmitting a notification, you should provide a pointer to where the data is located, and that is not relatead to BLE_GATTS_VLOC_STACK. When creating a characteristic, setting attr_md.vloc = BLE_GATTS_VLOC_STACK; means that "Attribute Value is located in stack memory, no user memory is required". This sets where the data in a characteristic is stored, and that is independent of the "origin" of the data to transmit in a notification.

In the ble_app_uart example in SDK 6.0.0 in the \Board\pca10001\s110\experimental-folder, notifications are transmitted using sd_ble_gatt_hvx(..) the following way:

uint32_t ble_nus_send_string(ble_nus_t * p_nus, uint8_t * string, uint16_t length)
{
   ble_gatts_hvx_params_t hvx_params;

   if (p_nus == NULL)
   {
       return NRF_ERROR_NULL;
   }

   if ((p_nus->conn_handle == BLE_CONN_HANDLE_INVALID) || (!p_nus->is_notification_enabled))
   {
       return NRF_ERROR_INVALID_STATE;
   }

   if (length > BLE_NUS_MAX_DATA_LEN)
   {
       return NRF_ERROR_INVALID_PARAM;
   }

   memset(&hvx_params, 0, sizeof(hvx_params));

   hvx_params.handle = p_nus->rx_handles.value_handle;
   hvx_params.p_data = string;
   hvx_params.p_len  = &length;
   hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;

   return sd_ble_gatts_hvx(p_nus->conn_handle, &hvx_params);
}

[leo]

Hey Kristin, thanks for your reply and sorry for the delay. Alright, thus it would be possible to set the location of the memory of the characteristic to 'BLE_GATTS_VLOC_STACK;', thus if the client writes something in the characteristic he writes on the stack. But, if i want to notify the client, i can use a other memory location (just for the notification) and the actual value of the characteristic stays the same?