diff --git a/src/knx/bits.h b/src/knx/bits.h
index c5ce526f..fe58f48d 100644
--- a/src/knx/bits.h
+++ b/src/knx/bits.h
@@ -94,6 +94,14 @@ void printHex(const char* suffix, const uint8_t *data, size_t length, bool newli
 #define printHex(...)   do {} while(0)
 #endif
 
+#ifdef KNX_ACTIVITYCALLBACK
+#define KNX_ACTIVITYCALLBACK_DIR 0x00
+#define KNX_ACTIVITYCALLBACK_DIR_RECV 0x00
+#define KNX_ACTIVITYCALLBACK_DIR_SEND 0x01
+#define KNX_ACTIVITYCALLBACK_IPUNICAST 0x02
+#define KNX_ACTIVITYCALLBACK_NET 0x04
+#endif
+
 const uint8_t* popByte(uint8_t& b, const uint8_t* data);
 const uint8_t* popWord(uint16_t& w, const uint8_t* data);
 const uint8_t* popInt(uint32_t& i, const uint8_t* data);
diff --git a/src/knx/data_link_layer.cpp b/src/knx/data_link_layer.cpp
index b75c1ecc..e2f601e2 100644
--- a/src/knx/data_link_layer.cpp
+++ b/src/knx/data_link_layer.cpp
@@ -9,6 +9,9 @@
 DataLinkLayer::DataLinkLayer(DeviceObject& devObj, NetworkLayerEntity& netLayerEntity, Platform& platform) :
     _deviceObject(devObj), _networkLayerEntity(netLayerEntity), _platform(platform)
 {
+#ifdef KNX_ACTIVITYCALLBACK
+    _netIndex = netLayerEntity.getEntityIndex();
+#endif
 }
 
 #ifdef USE_CEMI_SERVER
diff --git a/src/knx/data_link_layer.h b/src/knx/data_link_layer.h
index 9e4d6884..0270d31f 100644
--- a/src/knx/data_link_layer.h
+++ b/src/knx/data_link_layer.h
@@ -42,5 +42,8 @@ class DataLinkLayer
     Platform& _platform;
 #ifdef USE_CEMI_SERVER
     CemiServer* _cemiServer;
-#endif    
+#endif
+#ifdef KNX_ACTIVITYCALLBACK
+    uint8_t _netIndex = 0;
+#endif
 };
diff --git a/src/knx/ip_data_link_layer.cpp b/src/knx/ip_data_link_layer.cpp
index 43a7a595..b18f4d2a 100644
--- a/src/knx/ip_data_link_layer.cpp
+++ b/src/knx/ip_data_link_layer.cpp
@@ -30,6 +30,9 @@ bool IpDataLinkLayer::sendFrame(CemiFrame& frame)
     if(isSendLimitReached())
         return false;
     bool success = sendBytes(packet.data(), packet.totalLength());
+#ifdef KNX_ACTIVITYCALLBACK
+        knx.Activity((_netIndex << KNX_ACTIVITYCALLBACK_NET) | (KNX_ACTIVITYCALLBACK_DIR_SEND << KNX_ACTIVITYCALLBACK_DIR));
+#endif
     dataConReceived(frame, success);
     return success;
 }
@@ -51,6 +54,10 @@ void IpDataLinkLayer::loop()
         || buffer[1] != KNXIP_PROTOCOL_VERSION)
         return;
 
+#ifdef KNX_ACTIVITYCALLBACK
+    knx.Activity((_netIndex << KNX_ACTIVITYCALLBACK_NET) | (KNX_ACTIVITYCALLBACK_DIR_RECV << KNX_ACTIVITYCALLBACK_DIR));
+#endif
+
     uint16_t code;
     popWord(code, buffer + 2);
     switch ((KnxIpServiceType)code)
@@ -67,6 +74,9 @@ void IpDataLinkLayer::loop()
             KnxIpSearchResponse searchResponse(_ipParameters, _deviceObject);
 
             auto hpai = searchRequest.hpai();
+#ifdef KNX_ACTIVITYCALLBACK
+            knx.Activity((_netIndex << KNX_ACTIVITYCALLBACK_NET) | (KNX_ACTIVITYCALLBACK_DIR_SEND << KNX_ACTIVITYCALLBACK_DIR) | (KNX_ACTIVITYCALLBACK_IPUNICAST));
+#endif
             _platform.sendBytesUniCast(hpai.ipAddress(), hpai.ipPortNumber(), searchResponse.data(), searchResponse.totalLength());
             break;
         }
diff --git a/src/knx/network_layer_entity.cpp b/src/knx/network_layer_entity.cpp
index 6e51736d..6463d830 100644
--- a/src/knx/network_layer_entity.cpp
+++ b/src/knx/network_layer_entity.cpp
@@ -23,6 +23,11 @@ DptMedium NetworkLayerEntity::mediumType() const
     return _dataLinkLayer->mediumType();
 }
 
+uint8_t NetworkLayerEntity::getEntityIndex()
+{
+    return _entityIndex;
+}
+
 void NetworkLayerEntity::dataIndication(AckType ack, AddressType addrType, uint16_t destination, FrameFormat format, NPDU& npdu, Priority priority, uint16_t source)
 {
     _netLayer.dataIndication(ack, addrType, destination, format, npdu, priority, source, _entityIndex);
diff --git a/src/knx/network_layer_entity.h b/src/knx/network_layer_entity.h
index e20d6114..82db48cf 100644
--- a/src/knx/network_layer_entity.h
+++ b/src/knx/network_layer_entity.h
@@ -19,6 +19,7 @@ class NetworkLayerEntity
     DataLinkLayer& dataLinkLayer();
 
     DptMedium mediumType() const;
+    uint8_t getEntityIndex();
 
     // from data link layer
     void dataIndication(AckType ack, AddressType addType, uint16_t destination, FrameFormat format, NPDU& npdu,
diff --git a/src/knx/tpuart_data_link_layer.cpp b/src/knx/tpuart_data_link_layer.cpp
index 22bbf133..a17b2a4d 100644
--- a/src/knx/tpuart_data_link_layer.cpp
+++ b/src/knx/tpuart_data_link_layer.cpp
@@ -7,6 +7,7 @@
 #include "device_object.h"
 #include "address_table_object.h"
 #include "cemi_frame.h"
+#include "knx_facade.h"
 
 #include <stdio.h>
 #include <string.h>
@@ -546,8 +547,10 @@ TpUartDataLinkLayer::TpUartDataLinkLayer(DeviceObject& devObj,
 void TpUartDataLinkLayer::frameBytesReceived(uint8_t* buffer, uint16_t length)
 {
     //printHex("=>", buffer, length);
+#ifdef KNX_ACTIVITYCALLBACK
+    knx.Activity((_netIndex << KNX_ACTIVITYCALLBACK_NET) | (KNX_ACTIVITYCALLBACK_DIR_RECV << KNX_ACTIVITYCALLBACK_DIR));
+#endif
     CemiFrame frame(buffer, length);
-
     frameReceived(frame);
 }
 
@@ -653,6 +656,9 @@ bool TpUartDataLinkLayer::sendSingleFrameByte()
     if (_TxByteCnt >= _sendBufferLength)
     {
         _TxByteCnt = 0;
+#ifdef KNX_ACTIVITYCALLBACK
+        knx.Activity((_netIndex << KNX_ACTIVITYCALLBACK_NET) | (KNX_ACTIVITYCALLBACK_DIR_SEND << KNX_ACTIVITYCALLBACK_DIR));
+#endif
         return false;
     }
     return true;
diff --git a/src/knx_facade.h b/src/knx_facade.h
index 7facf61c..c1fb0ca9 100644
--- a/src/knx_facade.h
+++ b/src/knx_facade.h
@@ -70,6 +70,9 @@ typedef uint8_t* (*SaveCallback)(uint8_t* buffer);
 typedef void (*IsrFunctionPtr)();
 typedef void (*ProgLedOnCallback)();
 typedef void (*ProgLedOffCallback)();
+#ifdef KNX_ACTIVITYCALLBACK
+typedef void (*ActivityCallback)(uint8_t info);
+#endif
 
 template <class P, class B> class KnxFacade : private SaveRestore
 {
@@ -187,6 +190,21 @@ template <class P, class B> class KnxFacade : private SaveRestore
         _progLedOnCallback = progLedOnCallback;
     }
 
+#ifdef KNX_ACTIVITYCALLBACK
+    /// @brief sets the Callback Function indicating sent or received telegrams
+    /// @param activityCallback 
+    /// @details the info parameter 
+    void setActivityCallback(ActivityCallback activityCallback)
+    {
+        _activityCallback = activityCallback;
+    }
+
+    void Activity(uint8_t info)
+    {
+        if(_activityCallback)
+            _activityCallback(info);
+    }
+#endif
   
     int32_t buttonPin()
     {
@@ -414,6 +432,9 @@ template <class P, class B> class KnxFacade : private SaveRestore
     B& _bau;
     ProgLedOnCallback _progLedOnCallback = 0;
     ProgLedOffCallback _progLedOffCallback = 0;
+#ifdef KNX_ACTIVITYCALLBACK
+    ActivityCallback _activityCallback = 0;
+#endif
     uint32_t _ledPinActiveOn = KNX_LED_ACTIVE_ON;
     uint32_t _ledPin = KNX_LED;
     int32_t _buttonPin = KNX_BUTTON;