diff --git a/src/knx/bau27B0.cpp b/src/knx/bau27B0.cpp
index 3e66890..e1d0c53 100644
--- a/src/knx/bau27B0.cpp
+++ b/src/knx/bau27B0.cpp
@@ -10,9 +10,18 @@ using namespace std;
 Bau27B0::Bau27B0(Platform& platform)
     : BauSystemB(platform),
       _dlLayer(_deviceObj, _rfMediumObj, _addrTable, _netLayer, _platform)
+#ifdef USE_USBIF
+    , _cemiServer(_tunnelInterface, *this)
+    , _tunnelInterface(_deviceObj, _cemiServer, _platform)
+#endif      
 {
     _netLayer.dataLinkLayer(_dlLayer);
     _memory.addSaveRestore(&_rfMediumObj);
+#ifdef USE_USBIF
+    _cemiServer.dataLinkLayer(_dlLayer);
+    _dlLayer.cemiServer(_cemiServer);
+    _memory.addSaveRestore(&_cemiServerObject);
+#endif
 
     // Set Mask Version in Device Object depending on the BAU
     uint16_t maskVersion;
@@ -70,6 +79,18 @@ DataLinkLayer& Bau27B0::dataLinkLayer()
     return _dlLayer;
 }
 
+void Bau27B0::enabled(bool value)
+{
+    ::BauSystemB::enabled(value);
+    _tunnelInterface.enabled(value);
+}
+
+void Bau27B0::loop()
+{
+    ::BauSystemB::loop();
+    _tunnelInterface.loop();
+}
+
 void Bau27B0::domainAddressSerialNumberWriteIndication(Priority priority, HopCountType hopType, uint8_t* rfDoA,
                                                           uint8_t* knxSerialNumber)
 {
diff --git a/src/knx/bau27B0.h b/src/knx/bau27B0.h
index 544409d..39bddf6 100644
--- a/src/knx/bau27B0.h
+++ b/src/knx/bau27B0.h
@@ -4,11 +4,18 @@
 #include "rf_medium_object.h"
 #include "rf_physical_layer.h"
 #include "rf_data_link_layer.h"
+#ifdef USE_USBIF
+#include "usb_data_link_layer.h"
+#include "cemi_server.h"
+#include "cemi_server_object.h"
+#endif
 
 class Bau27B0 : public BauSystemB
 {
   public:
     Bau27B0(Platform& platform);
+    void enabled(bool value);
+    void loop();
 
   protected:
     InterfaceObject* getInterfaceObject(uint8_t idx);
@@ -18,6 +25,11 @@ class Bau27B0 : public BauSystemB
   private:
     RfDataLinkLayer _dlLayer;
     RfMediumObject _rfMediumObj;
+#ifdef USE_USBIF
+    CemiServer _cemiServer;
+    UsbDataLinkLayer _tunnelInterface;
+    CemiServerObject _cemiServerObject;
+#endif
 
     uint8_t _descriptor[2] = {0x27, 0xB0};
 #ifdef USE_USBIF
diff --git a/src/knx/bau_systemB.cpp b/src/knx/bau_systemB.cpp
index b8dd785..9840c0d 100644
--- a/src/knx/bau_systemB.cpp
+++ b/src/knx/bau_systemB.cpp
@@ -15,10 +15,6 @@ BauSystemB::BauSystemB(Platform& platform): _memory(platform), _addrTable(platfo
     _assocTable(platform), _groupObjTable(platform), _appProgram(platform),
     _platform(platform), _appLayer(_assocTable, *this),
     _transLayer(_appLayer, _addrTable), _netLayer(_transLayer)
-#ifdef USE_USBIF
-    , _dlLayerUsb(_deviceObj, _addrTable, _netLayer, _platform),
-      _cemiServer(_dlLayerUsb, *this)    
-#endif      
 {
     _appLayer.transportLayer(_transLayer);
     _transLayer.networkLayer(_netLayer);
@@ -27,17 +23,11 @@ BauSystemB::BauSystemB(Platform& platform): _memory(platform), _addrTable(platfo
     _memory.addSaveRestore(&_addrTable);
     _memory.addSaveRestore(&_assocTable);
     _memory.addSaveRestore(&_groupObjTable);
-#ifdef USE_USBIF
-    _memory.addSaveRestore(&_cemiServerObject);
-#endif    
 }
 
 void BauSystemB::loop()
 {
     dataLinkLayer().loop();
-#ifdef USE_USBIF
-    _dlLayerUsb.loop();
-#endif
     _transLayer.loop();
     sendNextGroupTelegram();
     nextRestartState();
@@ -51,9 +41,6 @@ bool BauSystemB::enabled()
 void BauSystemB::enabled(bool value)
 {
     dataLinkLayer().enabled(value);
-#ifdef USE_USBIF
-    _dlLayerUsb.enabled(value);
-#endif    
 }
 
 void BauSystemB::sendNextGroupTelegram()
diff --git a/src/knx/bau_systemB.h b/src/knx/bau_systemB.h
index 6b65899..5ca0ff5 100644
--- a/src/knx/bau_systemB.h
+++ b/src/knx/bau_systemB.h
@@ -12,11 +12,6 @@
 #include "tpuart_data_link_layer.h"
 #include "platform.h"
 #include "memory.h"
-#ifdef USE_USBIF
-#include "usb_data_link_layer.h"
-#include "cemi_server.h"
-#include "cemi_server_object.h"
-#endif
 
 class BauSystemB : protected BusAccessUnit
 {
@@ -93,9 +88,4 @@ class BauSystemB : protected BusAccessUnit
     bool _configured = true;
     RestartState _restartState = Idle;
     uint32_t _restartDelay = 0;
-#ifdef USE_USBIF
-    UsbDataLinkLayer _dlLayerUsb;
-    CemiServer _cemiServer;
-    CemiServerObject _cemiServerObject;
-#endif
 };
\ No newline at end of file
diff --git a/src/knx/cemi_server.cpp b/src/knx/cemi_server.cpp
index 2333525..301c22f 100644
--- a/src/knx/cemi_server.cpp
+++ b/src/knx/cemi_server.cpp
@@ -6,14 +6,79 @@
 #include "bits.h"
 #include <stdio.h>
 
-CemiServer::CemiServer(UsbDataLinkLayer& dlLayer, BusAccessUnit& bau):
-    _dlLayer(dlLayer),
+CemiServer::CemiServer(UsbDataLinkLayer& tunnelInterface, BusAccessUnit& bau):
+    _tunnelInterface(tunnelInterface),
     _bau(bau)
 {
 }
 
-#pragma region DLL Callbacks
+void CemiServer::dataLinkLayer(DataLinkLayer& layer)
+{
+    _dataLinkLayer = &layer;
+}
 
+void CemiServer::dataIndicationToTunnel(CemiFrame& frame)
+{
+    _tunnelInterface.sendCemiFrame(frame);
+}
+
+void CemiServer::frameReceived(CemiFrame& frame)
+{
+    switch(frame.messageCode())
+    {
+        case L_data_req:
+        {
+            // Send as indication to data link layer
+            frame.messageCode(L_data_ind);
+            _dataLinkLayer->dataIndicationFromTunnel(frame);
+            
+            // Send local reply to tunnel
+            frame.messageCode(L_data_con);
+            _tunnelInterface.sendCemiFrame(frame);
+            break;
+        }
+
+        case M_PropRead_req:
+        {
+            break;
+        }
+
+        case M_PropWrite_req:
+        {
+            break;
+        }
+
+        case M_FuncPropCommand_req:
+        {
+            break;
+        }
+
+        case M_FuncPropStateRead_req:
+        {
+            break;
+        }
+
+        case M_Reset_req:
+        {
+            break;
+        }
+
+        // we should not receive this: server -> client
+        case L_data_con:
+        case L_data_ind:
+        case M_PropInfo_ind:
+        case M_PropRead_con:
+        case M_PropWrite_con:
+        case M_FuncPropCommand_con:
+        //case M_FuncPropStateRead_con: // same value as M_FuncPropCommand_con
+        case M_Reset_ind:
+        default:
+            break;
+    }
+    _dataLinkLayer->dataIndicationFromTunnel(frame);
+}
+
+/*
 void CemiServer::propertyValueReadRequest(AckType ack, Priority priority, HopCountType hopType, uint16_t asap, 
     uint8_t objectIndex, uint8_t propertyId, uint8_t numberOfElements, uint16_t startIndex)
 {
@@ -176,3 +241,5 @@ void CemiServer::individualConfirm(AckType ack, HopCountType hopType, Priority p
             break;
     }
 }
+
+*/
\ No newline at end of file
diff --git a/src/knx/cemi_server.h b/src/knx/cemi_server.h
index e829004..3e93b4f 100644
--- a/src/knx/cemi_server.h
+++ b/src/knx/cemi_server.h
@@ -5,6 +5,9 @@
 
 class UsbDataLinkLayer;
 class BusAccessUnit;
+class DataLinkLayer;
+class CemiFrame;
+
 /**
  * This is an implementation of the cEMI server as specified in @cite knx:3/6/3.
  * Overview on page 57.
@@ -18,18 +21,22 @@ class CemiServer
   public:
     /**
      * The constructor.
-     * @param assocTable The AssociationTable is used to translate between asap (i.e. group objects) and group addresses.
+     * @param tunnelInterface The TunnelInterface of the KNX tunnel (e.g. USB or KNXNET/IP)
      * @param bau methods are called here depending of the content of the APDU
      */
-    CemiServer(UsbDataLinkLayer& dlLayer, BusAccessUnit& bau);
+    CemiServer(UsbDataLinkLayer& tunnelInterface, BusAccessUnit& bau);
+
+    void dataLinkLayer(DataLinkLayer& layer);
 
     // from data link layer
-#pragma region Data - Link - Layer - Callbacks
-    void dataIndividualIndication(HopCountType hopType, Priority priority, uint16_t source, APDU& apdu);
-    void dataIndividualConfirm(AckType ack, HopCountType hopType, Priority priority, uint16_t tsap, APDU& apdu, bool status);
-#pragma endregion
+    // Only L_Data service
+    void dataIndicationToTunnel(CemiFrame& frame);
 
-#pragma region from bau
+    // From tunnel interface
+    void frameReceived(CemiFrame& frame);
+
+
+/*
     void propertyValueReadRequest(AckType ack, Priority priority, HopCountType hopType, uint16_t asap,
                                   uint8_t objectIndex, uint8_t propertyId, uint8_t numberOfElements, uint16_t startIndex);
     void propertyValueReadResponse(AckType ack, Priority priority, HopCountType hopType, uint16_t asap, uint8_t objectIndex,
@@ -41,15 +48,16 @@ class CemiServer
     void propertyDescriptionReadResponse(AckType ack, Priority priority, HopCountType hopType, uint16_t asap,
                                          uint8_t objectIndex, uint8_t propertyId, uint8_t propertyIndex, bool writeEnable, uint8_t type,
                                          uint16_t maxNumberOfElements, uint8_t access);
-#pragma endregion
-
+*/
   private:
+/*  
     void propertyDataSend(ApduType type, AckType ack, Priority priority, HopCountType hopType, uint16_t asap,
                           uint8_t objectIndex, uint8_t propertyId, uint8_t numberOfElements, uint16_t startIndex, uint8_t* data,
                           uint8_t length);
     void individualIndication(HopCountType hopType, Priority priority, uint16_t tsap, APDU& apdu);
     void individualConfirm(AckType ack, HopCountType hopType, Priority priority, uint16_t tsap, APDU& apdu, bool status);
-
-    UsbDataLinkLayer& _dlLayer;
+*/
+    DataLinkLayer* _dataLinkLayer;
+    UsbDataLinkLayer& _tunnelInterface;
     BusAccessUnit& _bau;
 };
diff --git a/src/knx/data_link_layer.cpp b/src/knx/data_link_layer.cpp
index 92d34a6..14a3e9e 100644
--- a/src/knx/data_link_layer.cpp
+++ b/src/knx/data_link_layer.cpp
@@ -4,7 +4,7 @@
 #include "platform.h"
 #include "device_object.h"
 #include "address_table_object.h"
-
+#include "cemi_server.h"
 
 DataLinkLayer::DataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab, 
     NetworkLayer& layer, Platform& platform) :
@@ -12,6 +12,16 @@ DataLinkLayer::DataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab,
 {
 }
 
+void DataLinkLayer::cemiServer(CemiServer& cemiServer)
+{
+    _cemiServer = &cemiServer;
+}
+
+void DataLinkLayer::dataIndicationFromTunnel(CemiFrame& frame)
+{
+}
+
+
 void DataLinkLayer::dataRequest(AckType ack, AddressType addrType, uint16_t destinationAddr, FrameFormat format, Priority priority, NPDU& npdu)
 {
     // Normal data requests and broadcasts will always be transmitted as (domain) broadcast with domain address for open media (e.g. RF medium) 
diff --git a/src/knx/data_link_layer.h b/src/knx/data_link_layer.h
index a08e524..5674ce6 100644
--- a/src/knx/data_link_layer.h
+++ b/src/knx/data_link_layer.h
@@ -5,6 +5,7 @@
 #include "address_table_object.h"
 #include "knx_types.h"
 #include "network_layer.h"
+#include "cemi_server.h"
 
 class DataLinkLayer
 {
@@ -12,6 +13,10 @@ class DataLinkLayer
     DataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab, NetworkLayer& layer,
                   Platform& platform);
 
+    void cemiServer(CemiServer& cemiServer);
+
+    void dataIndicationFromTunnel(CemiFrame& frame);
+
     // from network layer
     void dataRequest(AckType ack, AddressType addrType, uint16_t destinationAddr, FrameFormat format,
                      Priority priority, NPDU& npdu);
@@ -30,4 +35,5 @@ class DataLinkLayer
     AddressTableObject& _groupAddressTable;
     NetworkLayer& _networkLayer;
     Platform& _platform;
+    CemiServer* _cemiServer;
 };
diff --git a/src/knx/usb_data_link_layer.cpp b/src/knx/usb_data_link_layer.cpp
index 5592b2b..d9f84b1 100644
--- a/src/knx/usb_data_link_layer.cpp
+++ b/src/knx/usb_data_link_layer.cpp
@@ -15,7 +15,7 @@ Adafruit_USBD_HID usb_hid;
 
 // HID report descriptor using TinyUSB's template
 // Generic In Out with 64 bytes report (max)
-uint8_t const desc_hid_report[] =
+static uint8_t const desc_hid_report[] =
 {
   //TUD_HID_REPORT_DESC_GENERIC_INOUT(64)
  0x06, 0xA0, 0xFF, // Usage Page (Vendor Defined 0xFFA0)
@@ -235,10 +235,18 @@ void set_report_callback(uint8_t report_id, hid_report_type_t report_type, uint8
 void UsbDataLinkLayer::loop()
 {
     if (!_enabled)
+	{
         return;
+	}
+
+	if (!isTxQueueEmpty())
+	{
+		//loadNextTxFrame();
+		//sendKnxHidReport();
+	}
 }
 
-bool UsbDataLinkLayer::sendFrame(CemiFrame& frame)
+bool UsbDataLinkLayer::sendCemiFrame(CemiFrame& frame)
 {
     if (!_enabled)
         return false;
@@ -248,18 +256,11 @@ bool UsbDataLinkLayer::sendFrame(CemiFrame& frame)
     // the L_Data.con for the previous L_Data.req.
     addFrameTxQueue(frame);
 
-    // TODO: For now L_data.req is confirmed immediately (L_Data.con)
-    // see 3.6.3 p.80: L_Data.con shall be generated AFTER transmission of the corresponsing frame
-    // RF sender will never generate L_Data.con with C=1 (Error), but only if the TX buffer overflows
-    // The RF sender cannot detect if the RF frame was transmitted successfully or not according to the spec.
-    dataConReceived(frame, true);
-
     return true;
 }
 
-UsbDataLinkLayer::UsbDataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab,
-                                         NetworkLayer& layer, Platform& platform)
-    : DataLinkLayer(devObj, addrTab, layer, platform)
+UsbDataLinkLayer::UsbDataLinkLayer(DeviceObject& deviceObject, CemiServer& cemiServer, Platform& platform)
+    : _deviceObject(deviceObject), _cemiServer(cemiServer), _platform(platform)
 {
 }
 
@@ -267,26 +268,14 @@ void UsbDataLinkLayer::frameBytesReceived(uint8_t* _buffer, uint16_t length)
 {
     // Prepare the cEMI frame
     CemiFrame frame(_buffer, length);
-/*            
-    frame.frameType(ExtendedFrame);         // KNX RF uses only extended frame format
-    frame.priority(SystemPriority);         // Not used in KNX RF
-    frame.ack(AckDontCare);                 // Not used in KNX RF 
-    frame.systemBroadcast(systemBroadcast); // Mapped from flag AddrExtensionType (KNX serial(0) or Domain Address(1))
-    frame.hopCount(hopCount);               // Hop count from routing counter
-    frame.addressType(addressType);         // Group address or individual address
-    frame.rfSerialOrDoA(&rfPacketBuf[4]);   // Copy pointer to field Serial or Domain Address (check broadcast flag what it is exactly)
-    frame.rfInfo(rfPacketBuf[3]);           // RF-info field (1 byte)
-    frame.rfLfn(lfn);                       // Data link layer frame number (LFN field)
-*/
 
-/*
-    print(" len: ");
-    print(newLength);
+    print("cEMI USB RX len: ");
+    print(length);
 
     print(" data: ");
-    printHex(" data: ", _buffer, newLength);
-*/
-    frameRecieved(frame);
+    printHex(" data: ", _buffer, length);
+
+    _cemiServer.frameReceived(frame);
 }
 
 void UsbDataLinkLayer::enabled(bool value)
@@ -329,12 +318,11 @@ void UsbDataLinkLayer::addFrameTxQueue(CemiFrame& frame)
     tx_frame->data = new uint8_t[tx_frame->length];
     tx_frame->next = NULL;
 
-/*
-    print(" len: ");
-    print(totalLength);
+    print("cEMI USB TX len: ");
+    print(tx_frame->length);
+
+    printHex(" data:", tx_frame->data, tx_frame->length);
 
-    printHex(" data:", tx_frame->data, totalLength);
-*/
     if (_tx_queue.back == NULL)
     {
         _tx_queue.front = _tx_queue.back = tx_frame;
diff --git a/src/knx/usb_data_link_layer.h b/src/knx/usb_data_link_layer.h
index eb1f1fb..0c1ede9 100644
--- a/src/knx/usb_data_link_layer.h
+++ b/src/knx/usb_data_link_layer.h
@@ -3,25 +3,26 @@
 #include <stdint.h>
 #include <Adafruit_TinyUSB.h>
 #include "data_link_layer.h"
+#include "cemi_server.h"
 
 #define MAX_KNX_TELEGRAM_SIZE 263
 
 extern Adafruit_USBD_HID usb_hid;
 
-class UsbDataLinkLayer : public DataLinkLayer
-{
-    using DataLinkLayer::_deviceObject;
-    using DataLinkLayer::_groupAddressTable;
-    using DataLinkLayer::_platform;
+class DeviceObject;
+class Platform;
 
+class UsbDataLinkLayer
+{
   public:
-    UsbDataLinkLayer(DeviceObject& devObj, AddressTableObject& addrTab, NetworkLayer& layer,
-                        Platform& platform);
+    UsbDataLinkLayer(DeviceObject& deviceObject, CemiServer& cemiServer, Platform& platform);
 
     void loop();
     void enabled(bool value);
     bool enabled() const;
 
+    bool sendCemiFrame(CemiFrame& frame);
+
   private:
     bool _enabled = false;
     uint8_t _loopState = 0;
@@ -43,10 +44,12 @@ class UsbDataLinkLayer : public DataLinkLayer
         _tx_queue_frame_t* back = NULL;
     } _tx_queue;
 
+    DeviceObject& _deviceObject;
+    CemiServer& _cemiServer;
+    Platform& _platform;
 
     void addFrameTxQueue(CemiFrame& frame);
     bool isTxQueueEmpty();
     void loadNextTxFrame(uint8_t** sendBuffer, uint16_t* sendBufferLength);
-    bool sendFrame(CemiFrame& frame);
     void frameBytesReceived(uint8_t* buffer, uint16_t length);
 };