https://devzone.nordicsemi.com/f/nordic-q-a/9073/sd_ble_gatts_hvx-error-code-0x3401-ins130Hiii, I am working on the ble_central_and_peripheral program(s130) in sdk8.1.0 .I could connect the device to the MCP and on clicking enable service we gets the notification. what actually happens when we click the enable service?? what i have understooden-USTelligent Community 13Mon, 07 Sep 2015 09:21:48 GMThttps://devzone.nordicsemi.com/thread/33394?ContentTypeID=1Mon, 07 Sep 2015 09:21:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d17adc8e-110f-4913-a8e1-1f8cfbe2bd14MartinBL<p>Hi</p> <p>The 0x3401 error is the <em>BLE_ERROR_GATTS_SYS_ATTR_MISSING</em> event indicating that some system attributes are missing. This means that you probably haven&#39;t enebaled notification of your characteristic by writing to the <a href="https://developer.bluetooth.org/gatt/descriptors/Pages/DescriptorViewer.aspx?u=org.bluetooth.descriptor.gatt.client_characteristic_configuration.xml">Client Characteristic Configuration descriptor</a> (CCCD). I am not skilled in Android programming, but I believe there is a method for enabling notifications: <a href="https://developer.android.com/reference/android/bluetooth/BluetoothGatt.html#setCharacteristicNotification">setCharacteristicNotification</a>. There are a lot of <a href="https://devzone.nordicsemi.com/questions/scope:all/sort:answers-desc/page:1/query:BLE_ERROR_GATTS_SYS_ATTR_MISSING/">questions about return code 0x3401</a> and Ole Morten has a good explanation <a href="https://devzone.nordicsemi.com/question/6085/strange-error-code-13313-0x3401-returned-by-sd_ble_gatts_hvx/">here</a>.</p><div style="clear:both;"></div>