diff --git a/speedclock.h b/speedclock.h
index 55e173e..682aca2 100644
--- a/speedclock.h
+++ b/speedclock.h
@@ -20,7 +20,7 @@ typedef enum {BASESTATION = 0, TOPSTATION} radio_type_e;
 
 typedef struct transcv_struct{
   unsigned long topstationtime;         // the top station sends its time (millis()) continously to the base station
-  unsigned long topbuttonpressedtime;   // the top station sends the time in millis() when the button was pressed - this is already the calculated time
+  volatile unsigned long topbuttonpressedtime;   // the top station sends the time in millis() when the button was pressed - this is already the calculated time
 }transcv_s;
 
 #define MIN_DELAY_BETWEEN_SEND_MS 1000    // this defines the time in milliseconds before the next set of data will be send to the base station - except the button was pressed.
@@ -38,7 +38,7 @@ const uint8_t BUTTONPins[NO_LAST_BUTTON] = {
   [BUTTON_FAIL]   = 3,                    // stop button input pin
 };
 
-#define MIN_DELAY_BETWEEN_PRESSED_MS 1000 // this defines the time in milliseconds before the button is expected to be pressed again. We do this to avaoid keybouncing
+#define MIN_DELAY_BETWEEN_PRESSED_MS 500 // this defines the time in milliseconds before the button is expected to be pressed again. We do this to avaoid keybouncing
 
 #define PIEZO_PIN 6                      // piezo speaker
 
@@ -102,7 +102,7 @@ void failSequence(void);
 void wait(unsigned long ms);
 void start_isr(void);
 void update_buttons(void);
-
-
+void send_values(void);
+void stop_isr(void);
 
 #endif
diff --git a/speedclock.ino b/speedclock.ino
index 6a5089d..0fa2c05 100644
--- a/speedclock.ino
+++ b/speedclock.ino
@@ -91,6 +91,8 @@ void setup(){
   radio.begin();
   radio.setRetries(15, 15);               //the first is the time between reties in multiple of 250ms, the second is the numer of attempts
   if(stationNumber == TOPSTATION){
+    // Attach the STOP button interrupt
+    attachInterrupt(digitalPinToInterrupt(BUTTONPins[BUTTON_STOPCANCEL]), stop_isr, FALLING );
     // Set the PA Level of the sendin TOP_STATION
     radio.setPALevel(RF24_PA_LEVEL);
     radio.openWritingPipe(addresses[1]);        // Both radios listen on the same pipes by default, but opposite addresses
@@ -120,113 +122,83 @@ void loop(void) {
     blink_on_swiched_at = millis();
     blink_on = !blink_on;
   }
+
+  // set state to new_state
+  if(timer_state != timer_new_state){
+    Serial.print(millis());
+    Serial.print("ms : current state:");
+    Serial.print(timer_state);
+    Serial.print(" new state:");
+    Serial.println(timer_new_state);
+  }
+
+  // update button states ...
+  update_buttons();
+    
 /****************** Code for the TOPSTATION is here - the stop button is connected to the top station ***************************/
-  
   if (stationNumber == TOPSTATION){                         // Radio is the top station and sends continously its time and the time the stop button was pressed.
 
-    
+    // send data to base_station
+    send_values();
 
-    if(false == offset_sync_sequence){
-      // check for pressed button ...  
-      if(topbuttonwaspressed == false){
-        if( (millis() - radio_data.topbuttonpressedtime) > MIN_DELAY_BETWEEN_PRESSED_MS){
-          // ignore if the button was "pressed" a few millis before - this is keybouncing and would give a false result and if the button is pressed for a longer time that would effect the time as well
-          if(digitalRead(BUTTONPins[BUTTON_STOPCANCEL]) != BUTTON_NOTPRESSED){
-            // button was pressed - store the time 
-            radio_data.topbuttonpressedtime = millis();
-            topbuttonwaspressed = true;
-            digitalWrite(LEDPins[RUN_LED], LED_ON);
-          }
-        }
-      } else {
-        if(digitalRead(BUTTONPins[BUTTON_STOPCANCEL]) == BUTTON_NOTPRESSED){
-          topbuttonwaspressed = false;
-          digitalWrite(LEDPins[RUN_LED], LED_OFF);
-        }
-      }
-    } else {
-      topbuttonwaspressed = false;
-      digitalWrite(LEDPins[RUN_LED], LED_OFF);
-    }
-        
-    // if the button was not pressed only each few second data will be send to BASESTATION ... 
-    if(offset_sync_sequence || topbuttonwaspressed || ((millis()-radio_data.topstationtime) >= MIN_DELAY_BETWEEN_SEND_MS)){
-      // store current millis to be send as reference ...
-      radio_data.topstationtime = millis();                       // set the current milli second count   
-      //Serial.print("senddate_to_base at:");
-      //Serial.println(millis());
-      //Serial.print(" -> topstationtime:");
-      //Serial.print(radio_data.topstationtime);
-      //Serial.print("ms  stoppressedtime:");
-      //Serial.print(radio_data.topbuttonpressedtime);
-      //Serial.print("ms  offset counter value :");
-      //Serial.println(counter_time_offset);
+    timer_state = timer_new_state;
 
-      // send data ...                                       
-      if (!radio.write(&radio_data,sizeof(radio_data))){                     // Send the counter variable to the other radio 
-        if(((millis() - connection_last_established_at_ms) >= (CONN_TIMEOUT-100)) || (connection_last_established_at_ms == 0)){ 
-          connection_available = false;
-          //Serial.println("Failed to send data to BASESSTATION ... will retry");
-          digitalWrite(LEDPins[FAIL_LED], LED_ON);
-          digitalWrite(LEDPins[READY_LED], LED_OFF);
-          offset_sync_sequence = true;
-          counter_time_offset = 0;
+    // set LEDs
+    set_state_LEDs(timer_state, false );
+
+    switch(timer_state){
+      case TIMER_NOCONNECTION:
+        // as long as there is no connection to BASE_STATION we will end up here
+        if(true == connection_available){
+          timer_new_state = TIMER_INIT;
+        }
+        offset_sync_sequence = true;
+        counter_time_offset = 0;
+        break;
+      case TIMER_INIT:
+        if(false == connection_available){
+          timer_new_state = TIMER_NOCONNECTION;
         } else {
-          if(offset_sync_sequence){
-            if(counter_time_offset > 0){
-              counter_time_offset--;
+          if(false == offset_sync_sequence){
+            if(button_state[BUTTON_STOPCANCEL] == BUTTON_NOTPRESSED){
+              topbuttonwaspressed = false;
+              timer_new_state = TIMER_IDLE;
             }
           }
         }
-      }  
-      else
-      {
-        //Serial.print("Data sent to BASESSTATION");   
-        digitalWrite(LEDPins[FAIL_LED], LED_OFF);
-        if(offset_sync_sequence){
-          digitalWrite(LEDPins[FAIL_LED], blink_on);
+        break;
+      case TIMER_IDLE:
+        //check for the pressed button - or better enable the interrupt to handle that
+        if(false == connection_available){
+          timer_new_state = TIMER_NOCONNECTION;
         } else {
-          digitalWrite(LEDPins[READY_LED], LED_ON);
+          if(true == topbuttonwaspressed){
+            timer_new_state = TIMER_STOPPED;
+          }
         }
-        connection_last_established_at_ms = millis();
-        connection_available = true;
-        // check offset sync counter ...
-        if(counter_time_offset < (4*REQUIRED_NUMBER_MEANVALS)){
-          counter_time_offset++;          
-        } else {
-          // offset sync done
-          offset_sync_sequence = false;
+        break;
+      case TIMER_STOPPED:
+        // wait a few millis and  ... after that go back to idle ... 
+        if((signed long)(millis() - radio_data.topbuttonpressedtime) > MIN_DELAY_BETWEEN_PRESSED_MS){
+          if(button_state[BUTTON_STOPCANCEL] == BUTTON_NOTPRESSED){
+            timer_new_state = TIMER_IDLE;
+            topbuttonwaspressed = false;
+          }
         }
-          
-      }
-       
+        break;
     }
 
-    //Serial.print("looptime_top ");
-    //Serial.println(millis());
   }
 
 /****************** Code for the BASESTATION is here - the display and the start button is connected here. All caclulation will be done here ***************************/
-
   if ( stationNumber == BASESTATION ) {
 
-    // update button states ...
-    update_buttons();
-
     // receive data from top_station, calculate offset and set 'last connection' time stamp
     receive_values();
 
     // update the OLED screen 
     update_screen(timer_new_state);
 
-    // set state to new_state
-    if(timer_state != timer_new_state){
-      //Serial.print(millis());
-      //Serial.print("ms : current state:");
-      //Serial.print(timer_state);
-      //Serial.print(" new state:");
-      //Serial.println(timer_new_state);
-    }
     timer_state = timer_new_state;
 
     // set LEDs
@@ -238,6 +210,7 @@ void loop(void) {
         if(connection_available == true){
           timer_new_state = TIMER_INIT;
         }
+        break;
       case TIMER_INIT:
         // init the system offset ... 
         if(connection_available == false){
@@ -382,13 +355,16 @@ void loop(void) {
         }
         break;
     }
-
-    //Serial.print("looptime_base ");
-    //Serial.println(millis());
-    
   }
-}
 
+  //Serial.print("mean_time_offset ");
+  //Serial.println(mean_time_offset);
+  //Serial.print("current_time_offset ");
+  //Serial.println(current_time_offset);
+  //Serial.print("looptime ");
+  //Serial.println(millis());
+  
+}
 
 //####################### HELPER FUNCTIONS ###########################
 void update_buttons(void){
@@ -453,14 +429,16 @@ void receive_values(void){
       connection_last_established_at_ms = millis();
       connection_available = true;
       current_time_offset = radio_data.topstationtime - millis();                             // the offset between TOP_STATION and BASESTATION 
-      //Serial.print("Current time on host in millis:");
-      //Serial.print(millis());
-      //Serial.print(" Current time on client in millis: ");
-      //Serial.println(radio_data.topstationtime);
-      //Serial.print("Offset is: ");
-      //Serial.println(current_time_offset);
-      //Serial.print(" Button was pressed last time on client in millis: ");
-      //Serial.println(radio_data.topbuttonpressedtime); 
+      /*
+      Serial.print("Current time on host in millis:");
+      Serial.print(millis());
+      Serial.print(" Current time on client in millis: ");
+      Serial.println(radio_data.topstationtime);
+      Serial.print("Offset is: ");
+      Serial.println(current_time_offset);
+      Serial.print(" Button was pressed last time on client in millis: ");
+      Serial.println(radio_data.topbuttonpressedtime); 
+      */
   
       // offset calculation ... only needed if the variation is bigger than allowed or not enough values available already ...
       if(counter_time_offset == 0){
@@ -697,7 +675,18 @@ void failSequence(void){
   }
 }
 
-void false_start_isr(void){
+void stop_isr(void){
+  // this is the interrupt routine for the topstation STOP button
+  // this will save the time when the runner has pushed the button
+  if(timer_state == TIMER_IDLE){
+    radio_data.topbuttonpressedtime = millis();
+    //Serial.print(radio_data.topbuttonpressedtime);
+    //Serial.println(" ms <- current time ** stop_ISR ** stop button pushed: ");
+    topbuttonwaspressed = true;   
+  }
+}
+
+void false_start_isr(void) {
   // this is the interrupt routine for the FALSESTART button
   // this will save the time when the runner is really started
   if(timer_new_state != TIMER_READY){
@@ -741,3 +730,47 @@ void start_isr(void){
   }
 }
 
+void send_values(void){
+  if(offset_sync_sequence || topbuttonwaspressed || ((millis()-radio_data.topstationtime) >= MIN_DELAY_BETWEEN_SEND_MS)){
+    // store current millis to be send as reference ...
+    radio_data.topstationtime = millis();                       // set the current milli second count   
+    //Serial.print("senddate_to_base at:");
+    //Serial.println(millis());
+    //Serial.print(" -> topstationtime:");
+    //Serial.print(radio_data.topstationtime);
+    //Serial.print("ms  stoppressedtime:");
+    //Serial.print(radio_data.topbuttonpressedtime);
+    //Serial.print("ms  offset counter value :");
+    //Serial.println(counter_time_offset);
+  
+    // send data ...                                       
+    if (!radio.write(&radio_data,sizeof(radio_data))){                     // Send the counter variable to the other radio 
+      if(((millis() - connection_last_established_at_ms) >= (CONN_TIMEOUT-100))){ 
+        connection_available = false;
+        //Serial.println("Failed to send data to BASESSTATION ... will retry");
+      } else {
+        if(offset_sync_sequence){
+          if(counter_time_offset > 0){
+            counter_time_offset--;
+          }
+        }
+      }
+    }  
+    else
+    {
+      //Serial.print("Data sent to BASESSTATION");   
+      connection_last_established_at_ms = millis();
+      connection_available = true;
+      // check offset sync counter ...
+      if(counter_time_offset < (4*REQUIRED_NUMBER_MEANVALS)){
+        counter_time_offset++;          
+      } else {
+        // offset sync done
+        offset_sync_sequence = false;
+      }
+        
+    }
+  }   
+}
+
+