Add callback mode for BUFFERED acquisition (CPPAPIS-18)

include/NI660Xsl/BufferedAcquisition.h

@@ -36,8 +36,10 @@ namespace ni660Xsl
   class NI660XSL_EXPORT BufferedAcquisition :public virtual CounterBasedOperation
   {
     public: 
+
         BufferedAcquisition(void);
         virtual ~BufferedAcquisition(void);
+
         /**
         * Configure the sample clock (rate at which data is saved in the buffer)
         * @param _sample_clk The pin of the sample clock.
@@ -45,21 +47,25 @@ namespace ni660Xsl
         * @param _max_rate The maximum expected rate of the clock in samples per seconds.
         */
         virtual void set_sample_clock(std::string _sample_clk, ni::EdgeType _active_edge, double _max_rate);
+
         /**
         * Set the buffer depth.
         * @param _nb_samples The buffer depth in samples per channel.
         */
         virtual void set_buffer_depth(unsigned long _nb_samples);
+
         /**
         * Set the overrun strategy
         * @param _strategy The strategy to apply.
         */
         virtual void set_overrun_strategy(ni::StrategyType _strategy);
+
         /**
         * Set the timeout (time to for data wait when entering get_buffer )
         * @param _timeout The time to wait in seconds.
         */
         virtual void set_timeout(double _timeout);
+
         /**
         * Set the timing to be finite or continuous.
         * If the chosen mode is finite, the acquisition will fill one buffer.
@@ -67,28 +73,40 @@ namespace ni660Xsl
         * @param _mode The mode to use.
         */
         virtual void set_timing_mode(ni::ModeType _mode);
+
         /**
         * Specifies the point in the buffer at which to begin a read operation.
         * @param _start_point The start point.
         * @param _offset The offset to apply to _start_point.
         */
         virtual void set_read_start_point(ni::StartPointType _start_point, unsigned long _offset);
+
         /**
-        * Start the acquisition of a raw buffer.
+        * Set the callback mode for buffered acquisition (default = disabled).
+        * @param _enabled True if callback mechanism is to be enabled.
+        */
+        virtual void set_callback_mode(bool _enabled);
+
+        /**
+        * Start the acquisition of a raw buffer (polling mecanism).
         */
         virtual void get_raw_buffer(void) throw (ni660Xsl::DAQException);
+
         /**
         * Start the acquisition of a scaled buffer.
         */
         virtual void get_scaled_buffer(void) throw (ni660Xsl::DAQException);
+
         /**
         * This function must be implemented by user. Will be called each time an overrun occurred.
         */
         virtual void handle_data_lost(void) = 0;
+
         /**
         * This function must be implemented by user. Will be called each time a timeout occurred.
         */
         virtual void handle_timeout(void) = 0;
+
         /**
         * This function must be implemented by user. 
         * Will be called each time a raw buffer has been received.
@@ -97,6 +115,7 @@ namespace ni660Xsl
         * @param _samples_read The actual number of samples read from each channel (returned value).
         */
         virtual void handle_raw_buffer(ni660Xsl::InRawBuffer* buffer, long& _samples_read) = 0;
+
         /**
         * This function must be implemented by user. 
         * Will be called each time a raw buffer has been received.
@@ -116,7 +135,7 @@ namespace ni660Xsl
         unsigned long offset_;
         double timeout_;
         ni::ModeType mode_;
-        
+        bool use_callback_;
     };
 
 }//namespace

include/NI660Xsl/BufferedEventCounting.h

@@ -28,6 +28,7 @@
 
 namespace ni660Xsl
 {
+
 // ============================================================================
 //!  Perform buffered event counting
 // ============================================================================
@@ -37,25 +38,32 @@ namespace ni660Xsl
 //! The rate at which data is saved is determined by a sample clock.
 //! 
 // ============================================================================
-    class NI660XSL_EXPORT BufferedEventCounting: public EventCounting, public BufferedAcquisition
+    class NI660XSL_EXPORT BufferedEventCounting:  public EventCounting, 
+                                                  public BufferedAcquisition
     {
       public:
-        BufferedEventCounting(void);
-        virtual ~BufferedEventCounting(void);
+
+        BufferedEventCounting();
+        virtual ~BufferedEventCounting();
         
         /**
         * Configure the hardware with all preconfigured parameters.
         */
-        virtual void configure(void) throw (ni660Xsl::DAQException);
+        virtual void configure(void) 
+          throw (ni660Xsl::DAQException);
         
         /**
-        * This function must be implemented by user. Will be called each time a overrun occurred.
+        * This function must be implemented by user. 
+        * Will be called each time a overrun occurred.
         */
-        virtual void handle_data_lost(void) = 0;
+        virtual void handle_data_lost() = 0;
+
         /**
-        * This function must be implemented by user. Will be called each time a timeout occurred.
+        * This function must be implemented by user. 
+        * Will be called each time a timeout occurred.
         */
-        virtual void handle_timeout(void) = 0;
+        virtual void handle_timeout() = 0;
+
         /**
         * This function must be implemented by user. 
         * Will be called each time a buffer has been received.

include/NI660Xsl/BufferedPositionMeasurement.h

@@ -34,23 +34,31 @@ namespace ni660Xsl
 //! The rate at which data is saved is determined by a sample clock.
 //! 
 // ============================================================================   
-    class NI660XSL_EXPORT BufferedPositionMeasurement: public PositionMeasurement, public BufferedAcquisition
+    class NI660XSL_EXPORT BufferedPositionMeasurement:  public PositionMeasurement, 
+                                                        public BufferedAcquisition
     {
       public:
-        BufferedPositionMeasurement(void);
-        virtual ~BufferedPositionMeasurement(void); 
+        BufferedPositionMeasurement();
+        virtual ~BufferedPositionMeasurement(); 
+
         /**
-        * Configure hardware with all predefined parameters
+        * Configure hardware with all predefined parameters.
         */
-        virtual void configure (void) throw (ni660Xsl::DAQException);
+        virtual void configure (void) 
+          throw (ni660Xsl::DAQException);
+
         /**
-        * This function must be implemented by user. Will be called each time a overrun occurred.
+        * This function must be implemented by user. 
+        * Will be called each time a overrun occurred.
         */
         virtual void handle_data_lost(void) = 0;
+
         /**
-        * This function must be implemented by user. Will be called each time a timeout occurred.
+        * This function must be implemented by user. 
+        * Will be called each time a timeout occurred.
         */
         virtual void handle_timeout(void) = 0;
+
         /**
         * This function must be implemented by user. 
         * Will be called each time a raw buffer has been received.
@@ -59,6 +67,7 @@ namespace ni660Xsl
         * @param _samples_read The actual number of samples read from each channel(returned value).
         */
         virtual void handle_raw_buffer(ni660Xsl::InRawBuffer* buffer, long& _samples_read) = 0;
+
         /**
         * This function must be implemented by user. 
         * Will be called each time a scaled buffer has been received.

include/NI660Xsl/EventCounting.h

@@ -36,18 +36,22 @@ namespace ni660Xsl
 class NI660XSL_EXPORT EventCounting: public InputOperation
 {
   public:
+
 	  EventCounting(void);
     virtual ~EventCounting(void);
+
     /**
     * Add an an input channel to an event counting operation. \n
 	  * It is only possible to add one channel.
 	  * @param _chan The channel to add.
     */
 	  virtual void add_input_channel(ni660Xsl::EventCountChan _chan);
+
     /**
-  * Configure the hardware
+    * Configure the hardware.
     */
 	  virtual void configure(void) = 0;
+
   protected:
 	  std::string chan_name_;
 	  ni::EdgeType edge_;
@@ -55,9 +59,9 @@ protected:
 	  ni::DirectionType count_direction_;
 	  int added_channels;
     std::string input_terminal_;
+	  
     // Configure the input channel.
     virtual void configure_channel(void) throw (ni660Xsl::DAQException);
-
 };
 
 }//namespace

include/NI660Xsl/InputOperation.h

@@ -64,7 +64,7 @@ class NI660XSL_EXPORT InputOperation : public virtual CounterBasedOperation
     virtual void set_min_pulse_width( double _min_pulse_width_seconds );
 
 		/**
-		* Configure hardware with all predefined parameters
+		* Configure hardware with all predefined parameters.
 		*/
 		virtual void configure (void) = 0;
     

include/NI660Xsl/NI.h

@@ -332,6 +332,21 @@ namespace ni{
         toggle = DAQmx_Val_Toggle
     }BehaviorType;
     
+/**
+* Event type for callback function.
+*/
+    typedef enum
+    {
+        /**
+        * Acquisition event type.
+        */
+        intoBuffer = DAQmx_Val_Acquired_Into_Buffer,
+        /**
+        * Generation event type.
+        */
+        fromBuffer = DAQmx_Val_Transferred_From_Buffer 
+    }CBEventType;
+
 }//namespace ni
 
 #endif // _NI_H_

include/NI660Xsl/PositionMeasurement.h

@@ -53,7 +53,7 @@ namespace ni660Xsl
 	*/
 	virtual void add_angular_encoder(ni660Xsl::AngularEncoderChan _chan) throw (ni660Xsl::DAQException);
 	/**
-	* Configure hardware with all predefined parameters
+	* Configure hardware with all predefined parameters.
 	*/
 	virtual void configure (void) = 0;
     protected:

src/BufferedAcquisition.cpp

@@ -33,7 +33,8 @@ strategy_(ni::abort),
 start_point_(ni::current_read_position),
 offset_(0),
 timeout_(1.0),
-mode_(ni::continuous)
+mode_(ni::continuous),
+use_callback_(false) 
 {
 }
 // ============================================================================
@@ -96,6 +97,13 @@ void BufferedAcquisition::set_read_start_point(ni::StartPointType _start_point,
     this->offset_ = _offset;
 }
 // ============================================================================
+// BufferedAcquisition::set_callback_mode
+// ============================================================================
+void BufferedAcquisition::set_callback_mode(bool _enabled)
+{
+	this->use_callback_ = _enabled;
+}
+// ============================================================================
 // BufferedAcquisition::get_raw_buffer
 // ============================================================================
 void BufferedAcquisition::get_raw_buffer(void) 
@@ -159,7 +167,7 @@ throw (ni660Xsl::DAQException)
 		this->handle_timeout();
 		delete rb;
 	}
-	//----------handle others errors---------------------------------------
+	//----------handle other errors---------------------------------------
   else if(err < 0)
   {
       delete rb;

src/BufferedEventCounting.cpp

@@ -22,16 +22,27 @@
 namespace ni660Xsl
 {
 
-  /*int32 CVICALLBACK BufferedEventCountingCallback (TaskHandle taskHandle, int32 everyNsamplesEventType, uInt32 nSamples, void *callbackData)
+// ============================================================================
+// raw_buffer_callback
+//
+// Callback function for buffered acquisition.
+// @param _taskHandle NI task handler.
+// @param _evt_type Event type associated to the callback function.
+// @param _samples Number of samples of the buffer.
+// @param _data Callback data pointer.
+// ============================================================================
+int32 CVICALLBACK raw_buffer_callback(ni::DAQTaskHandle _taskHandle, 
+                                      int32 _evt_type, 
+                                      uInt32 _samples, 
+                                      void *_data)
 {
+  //std::cout << "raw_buffer_callback() entering..." << std::endl;
 
-    std::cout <<"=-------------------------------------------------------------------" << std::endl;
-    std::cout << "Before get_raw_buffer from callback, for task handle: "<< taskHandle << std::endl;
-    reinterpret_cast<BufferedEventCounting*>(callbackData)->get_raw_buffer();
-    std::cout << "After get_raw_buffer from callback." << std::endl;
+  // call internal function to read data from board
+  reinterpret_cast<BufferedEventCounting*>(_data)->get_raw_buffer();
 
   return 0;
-  }*/
+}
 
 // ============================================================================
 // BufferedEventCounting::BufferedEventCounting
@@ -40,8 +51,8 @@ BufferedEventCounting::BufferedEventCounting()
 :EventCounting(),
 BufferedAcquisition()
 {
-//std::cout<<<<"BufferedEventCounting::BufferedEventCounting"<<std::endl;
 }
+
 // ============================================================================
 // BufferedEventCounting::~BufferedEventCounting
 // ============================================================================
@@ -49,13 +60,16 @@ BufferedEventCounting::~BufferedEventCounting()
 {
   //std::cout<<"BufferedEventCounting::~BufferedEventCounting"<<std::endl;
 }
+
 // ============================================================================
 // BufferedEventCounting::configure
 // ============================================================================
-void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
+void BufferedEventCounting::configure(void) 
+  throw (ni660Xsl::DAQException)
 {
   //std::cout<<<<"BufferedEventCounting::configure<-"<<std::endl;
 
+  //-------------------------configure channel------------------------------------------
   try
   {
     this->configure_channel();
@@ -69,20 +83,57 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     throw DAQException();
   }
 
+  //-------------------------configure timing------------------------------------------
+  const char* clk =  this->sample_clk_.c_str();
+
+  int err = DAQmxCfgSampClkTiming(this->task_handle_, clk, this->max_rate_, 
+    this->active_edge_, this->mode_, this->nb_samples_);
+  
+  if (err < 0)
+  {
+    throw ni660Xsl::DAQException("Timing configuration failed!",
+	    this->get_string_error(),
+	    "BufferedEventCounting::configure()",
+	    err);
+  }
+  else if (err > 0)
+  {
+    this->warn_ = this->get_string_error();
+    this->warn_occured_ = true;
+  }
+
+  if (this->use_callback_)
+  {
     //-------------------------Register callback event-------------------------------
-    //- Register a callback which will be called when the number of sample will be acquired
-    /*int err = DAQmxRegisterEveryNSamplesEvent (this->task_handle_, DAQmx_Val_Acquired_Into_Buffer , this->nb_samples_, 
-                                          0, &BufferedEventCountingCallback, static_cast<void*> (this));*/
+    //- Register a callback which will be called when the number of samples will be acquired.
+    err = DAQmxRegisterEveryNSamplesEvent(this->task_handle_, ni::intoBuffer, 
+                this->nb_samples_, 0, raw_buffer_callback, 
+                static_cast<void*> (this));
     
+    if (err < 0)
+    {
+	    throw ni660Xsl::DAQException("callback configuration failed!",
+	      this->get_string_error(),
+	      "BufferedEventCounting::configure()",
+	      err);
+    }
+    else if (err > 0)
+    {
+      this->warn_ = this->get_string_error();
+      this->warn_occured_ = true;
+    }
+  }
+
+  if (this->use_callback_)
+  {
+    //-------------------------reset acquisition buffer-------------------------------------------
+    err = DAQmxResetBufInputBufSize(this->task_handle_);
 
-    //-------------------------config timing------------------------------------------
-    const char* clk =  this->sample_clk_.c_str();
-    int err = DAQmxCfgSampClkTiming(this->task_handle_, clk, this->max_rate_, this->active_edge_, this->mode_, this->nb_samples_);
     if (err < 0)
     {
-	throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Buffer reset failed!",
 	      this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	      "BufferedEventCounting::configure()",
 	      err);
     }
     else if (err > 0)
@@ -90,13 +141,16 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
       this->warn_ = this->get_string_error();
       this->warn_occured_ = true;
     }
-    //-------------------------config buffer-------------------------------------------
+  }
+
+  //-------------------------configure acquisition buffer-------------------------------------------
   err = DAQmxCfgInputBuffer(this->task_handle_, this->nb_samples_);
+
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+	  throw ni660Xsl::DAQException("Buffer configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	    "BufferedEventCounting::configure()",
 	    err);
   }
   else if (err > 0)
@@ -104,13 +158,15 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-    //---------------------config read start point-----------------------------------
+  
+  //---------------------configure read start point-----------------------------------
   err = DAQmxSetReadRelativeTo(this->task_handle_, this->start_point_);
+  
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Start point configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	    "BufferedEventCounting::configure()",
 	    err);
   }
   else if (err > 0)
@@ -119,12 +175,14 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     this->warn_occured_ = true;
   }
     
+  //-------------------------configure offset-------------------------------
   err = DAQmxSetReadOffset(this->task_handle_, this->offset_);
+
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Offset configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	    "BufferedEventCounting::configure()",
 	    err);
   }
   else if (err > 0)
@@ -132,16 +190,18 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-	//-------------------------config tc------------------------------------------
+	
+  //-------------------------configure tc------------------------------------------
 	if( this->terminal_.size() != 0)
 	{
 		const char* term =  this->terminal_.c_str();
 		err = DAQmxSetExportedCtrOutEventOutputTerm(this->task_handle_, term);
+		
     if (err < 0)
 		{
-			throw ni660Xsl::DAQException("configuration failed",
+			throw ni660Xsl::DAQException("Output term configuration failed!",
 				this->get_string_error(),
-				"BufferedEventCounting::configure",
+				"BufferedEventCounting::configure()",
         err);
 		}
 		else if (err > 0)
@@ -149,12 +209,14 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
 			this->warn_ = this->get_string_error();
 			this->warn_occured_ = true;
 		}
+
 		err = DAQmxSetExportedCtrOutEventOutputBehavior(this->task_handle_, this->behavior_);
+		
     if (err < 0)
 		{
-			throw ni660Xsl::DAQException("configuration failed",
+			throw ni660Xsl::DAQException("Output behaviour configuration failed!",
 				this->get_string_error(),
-				"BufferedEventCounting::configure",
+				"BufferedEventCounting::configure()",
         err);
 		}
 		else if (err > 0)
@@ -164,17 +226,17 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
 		}
 	}
 
-	
-    //-------------------------config trigger------------------------------------------
+	//-------------------------configure start trigger------------------------------------------
   if (use_start_trig_)
   {
-	//config trigger to be arm start trig
+	  // configure trigger to be a "arm start trig"
 	  int err = DAQmxSetArmStartTrigType(this->task_handle_, DAQmx_Val_DigEdge);
+
 	  if(err < 0)
 	  {
-	    throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Start trigger configuration failed!",
         this->get_string_error(),
-		"BufferedEventCounting::configure",
+        "BufferedEventCounting::configure()",
         err);
     }
     else if(err > 0)
@@ -183,14 +245,16 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
 	    this->warn_occured_ = true;
     }
 	
-	//config trigger pin
+	  // configure trigger pin
 	  const char* s =  this->start_trigger_source_.c_str();
+
 	  err = DAQmxSetDigEdgeArmStartTrigSrc(this->task_handle_, s);
+
 	  if(err < 0)
 	  {
-	    throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Start trigger src configuration failed!",
         this->get_string_error(),
-		"BufferedEventCounting::configure",
+        "BufferedEventCounting::configure()",
         err);
     }
     else if (err > 0)
@@ -199,13 +263,14 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
 	    this->warn_occured_ = true;
     }
     
-	//config edge 
+    // configure edge 
     err = DAQmxSetDigEdgeArmStartTrigEdge(this->task_handle_, this->trig_active_edge_);
+    
     if (err < 0)
     {
-	    throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Start trigger edge configuration failed!",
         this->get_string_error(),
-		"BufferedEventCounting::configure",
+        "BufferedEventCounting::configure()",
         err);
     }
     else if (err > 0)
@@ -214,14 +279,16 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
 	    this->warn_occured_ = true;
     }
   }
-    //---------------------config autostart------------------------------------------------
+  
+  //---------------------configure autostart------------------------------------------------
   //to call get_buffer() does not start the acquisition.
   err = DAQmxSetReadAutoStart(this->task_handle_, FALSE);
+
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Autostart configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	    "BufferedEventCounting::configure()",
 	    err);
   }
   else if (err > 0)
@@ -229,13 +296,15 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-	//---------------------config read mode-----------------------------------------------
+	
+  //---------------------configure read mode-----------------------------------------------
 	err = DAQmxSetReadWaitMode(this->task_handle_, this->read_mode_);
+	
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("read mode configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure");
+	    "BufferedEventCounting::configure()");
   }
   else if (err > 0)
   {
@@ -257,7 +326,6 @@ void BufferedEventCounting::configure(void) throw (ni660Xsl::DAQException)
     throw DAQException();
   }
   
-
   //std::cout<<<<"BufferedEventCounting::configure->"<<std::endl;
 }
 

src/BufferedPositionMeasurement.cpp

@@ -20,6 +20,29 @@
 
 namespace ni660Xsl
 {
+
+// ============================================================================
+// scaled_buffer_callback
+//
+// Callback function for buffered acquisition.
+// @param _taskHandle NI task handler.
+// @param _evt_type Event type associated to the callback function.
+// @param _samples Number of samples of the buffer.
+// @param _data Callback data pointer.
+// ============================================================================
+int32 CVICALLBACK scaled_buffer_callback(ni::DAQTaskHandle _taskHandle, 
+                                         int32 _evt_type, 
+                                         uInt32 _samples, 
+                                         void *_data)
+{
+  //std::cout << "scaled_buffer_callback() entering..." << std::endl;
+
+  // call internal function to read data from board
+  reinterpret_cast<BufferedPositionMeasurement*>(_data)->get_scaled_buffer();
+
+  return 0;
+}
+
 // ============================================================================
 // BufferedPositionMeasurement::BufferedPositionMeasurement
 // ============================================================================
@@ -28,20 +51,23 @@ BufferedPositionMeasurement::BufferedPositionMeasurement()
 BufferedAcquisition()
 {
 }
+
 // ============================================================================
 // BufferedPositionMeasurement::~BufferedPositionMeasurement
 // ============================================================================
 BufferedPositionMeasurement::~BufferedPositionMeasurement()
 {
 }
+
 // ============================================================================
 // BufferedPositionMeasurement::configure
 // ============================================================================
-void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException)
+void BufferedPositionMeasurement::configure (void) 
+  throw (ni660Xsl::DAQException)
 { 
-    
   //std::cout<<<<"BufferedPositionMeasurement::configure<-"<<std::endl;
 
+  //-------------------------configure channel------------------------------------------
   try
   {
     this->configure_channel();
@@ -54,15 +80,19 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
   {
     throw DAQException();
   }
-    //-------------------------config timing------------------------------------------
+  
+  //-------------------------configure timing------------------------------------------
   //std::cout<<<<"BufferedPositionMeasurement::config timing"<<std::endl;
   const char* clk =  this->sample_clk_.c_str();
-    int err = DAQmxCfgSampClkTiming(this->task_handle_, clk, this->max_rate_, this->active_edge_, this->mode_, this->nb_samples_);
+
+  int err = DAQmxCfgSampClkTiming(this->task_handle_, clk, this->max_rate_, 
+    this->active_edge_, this->mode_, this->nb_samples_);
+  
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Timing configuration failed!",
 	    this->get_string_error(),
-	    "BufferedPositionMeasurement::configure",
+	    "BufferedPositionMeasurement::configure()",
 	    err);
   }
   else if (err > 0)
@@ -70,14 +100,57 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-    //-------------------------config buffer-------------------------------------------
+
+  if (this->use_callback_)
+  {
+    //-------------------------Register callback event-------------------------------
+    //- Register a callback which will be called when the number of samples will be acquired.
+    err = DAQmxRegisterEveryNSamplesEvent(this->task_handle_, ni::intoBuffer, 
+                this->nb_samples_, 0, scaled_buffer_callback, 
+                static_cast<void*> (this));
+    
+    if (err < 0)
+    {
+	    throw ni660Xsl::DAQException("callback configuration failed!",
+	      this->get_string_error(),
+	      "BufferedPositionMeasurement::configure()",
+	      err);
+    }
+    else if (err > 0)
+    {
+      this->warn_ = this->get_string_error();
+      this->warn_occured_ = true;
+    }
+  }
+
+  if (this->use_callback_)
+  {
+    //-------------------------reset acquisition buffer-------------------------------------------
+    err = DAQmxResetBufInputBufSize(this->task_handle_);
+
+    if (err < 0)
+    {
+	    throw ni660Xsl::DAQException("Buffer reset failed!",
+	      this->get_string_error(),
+	      "BufferedPositionMeasurement::configure()",
+	      err);
+    }
+    else if (err > 0)
+    {
+      this->warn_ = this->get_string_error();
+      this->warn_occured_ = true;
+    }
+  }
+
+  //-------------------------configure buffer-------------------------------------------
 	//std::cout<<<<"BufferedPositionMeasurement::config buffer"<<std::endl;
   err = DAQmxCfgInputBuffer(this->task_handle_, this->nb_samples_);
+  
   if(err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Buffer configuration failed",
 	    this->get_string_error(),
-	    "BufferedPositionMeasurement::configure",
+	    "BufferedPositionMeasurement::configure()",
 	    err);
   }
   else if (err > 0)
@@ -85,16 +158,18 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-	//-------------------------config trigger------------------------------------------
+	
+  //-------------------------configure start trigger------------------------------------------
   if (use_start_trig_)
   {
-	//config trigger to be arm start trig
+	  //config trigger to be a "arm start trig"
 	  int err = DAQmxSetArmStartTrigType(this->task_handle_, DAQmx_Val_DigEdge);
+	
     if (err < 0)
 	  {
-	    throw ni660Xsl::DAQException("configuration failed",
+      throw ni660Xsl::DAQException("Start trigger configuration failed!",
         this->get_string_error(),
-		"BufferedPositionMeasurement::configure",
+		    "BufferedPositionMeasurement::configure()",
 		    err);
 	  }
     else if (err > 0)
@@ -103,14 +178,14 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
 	    this->warn_occured_ = true;
     }
 	
-	//config trigger pin
+	  // configure trigger pin
 	  const char* s =  this->start_trigger_source_.c_str();
 	  err = DAQmxSetDigEdgeArmStartTrigSrc(this->task_handle_, s);
 	  if(err < 0)
 	  {
-	    throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Start trigger src configuration failed!",
           this->get_string_error(),
-		"BufferedPositionMeasurement::configure",
+		      "BufferedPositionMeasurement::configure()",
 		      err);
     }
     else if (err > 0)
@@ -119,13 +194,14 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
 	    this->warn_occured_ = true;
     }
 	
-	//config edge 
+	  // configure edge 
 	  err = DAQmxSetDigEdgeArmStartTrigEdge(this->task_handle_, this->trig_active_edge_);
+	  
     if (err < 0)
     {
-	    throw ni660Xsl::DAQException("configuration failed",
+	    throw ni660Xsl::DAQException("Start trigger edge configuration failed!",
 		      this->get_string_error(),
-		"BufferedPositionMeasurement::configure",
+		      "BufferedPositionMeasurement::configure()",
 		      err);
     }
     else if (err > 0)
@@ -134,13 +210,15 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
 	    this->warn_occured_ = true;
     }
   }
-    //---------------------config read start point-----------------------------------
+  
+  //---------------------configure read start point-----------------------------------
   err = DAQmxSetReadRelativeTo(this->task_handle_, this->start_point_);
+
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Start point configuration failed!",
 	    this->get_string_error(),
-	    "BufferedPositionMeasurement::configure",
+	    "BufferedPositionMeasurement::configure()",
 	    err);
   }
   else if (err > 0)
@@ -149,12 +227,14 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_occured_ = true;
   }
     
+  //---------------------configure offset-----------------------------------
   err = DAQmxSetReadOffset(this->task_handle_, this->offset_);
+  
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Offset configuration failed!",
 	    this->get_string_error(),
-	    "BufferedPositionMeasurement::configure",
+	    "BufferedPositionMeasurement::configure()",
 	    err);
   }
   else if (err > 0)
@@ -162,16 +242,18 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-	//-------------------------config tc------------------------------------------
+	
+  //-------------------------configure tc------------------------------------------
 	if( this->terminal_.size() != 0)
 	{ 
 		const char* term =  this->terminal_.c_str();
 		err = DAQmxSetExportedCtrOutEventOutputTerm(this->task_handle_, term);
+
 		if (err < 0)
 		{
-			throw ni660Xsl::DAQException("configuration failed",
+			throw ni660Xsl::DAQException("Term configuration failed!",
 				this->get_string_error(),
-				"BufferedPositionMeasurement::configure",
+				"BufferedPositionMeasurement::configure()",
         err);
 		}
 		else if (err > 0)
@@ -179,10 +261,12 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
 			this->warn_ = this->get_string_error();
 			this->warn_occured_ = true;
 		}
+
 		err = DAQmxSetExportedCtrOutEventOutputBehavior(this->task_handle_, this->behavior_);
+
 		if (err < 0)
 		{
-			throw ni660Xsl::DAQException("configuration failed",
+			throw ni660Xsl::DAQException("term behaviour configuration failed()",
 				this->get_string_error(),
 				"BufferedPositionMeasurement::configure",
         err);
@@ -207,15 +291,17 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
 		}*/
 
 	}
-    //---------------------config autostart------------------------------------------
+   
+  //---------------------configure autostart------------------------------------------
 
   //to call get_buffer() does not start the acquisition.
   err = DAQmxSetReadAutoStart(this->task_handle_, FALSE);
+  
   if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Autostart configuration failed!",
 	    this->get_string_error(),
-	    "BufferedPositionMeasurement::configure",
+	    "BufferedPositionMeasurement::configure()",
 	    err);
   }
   else if (err > 0)
@@ -223,13 +309,15 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
-	//---------------------config read mode-----------------------------------------------
+	
+  //---------------------configure read mode-----------------------------------------------
 	err = DAQmxSetReadWaitMode(this->task_handle_, this->read_mode_);
+
 	if (err < 0)
   {
-	throw ni660Xsl::DAQException("configuration failed",
+    throw ni660Xsl::DAQException("Read mode configuration failed!",
 	    this->get_string_error(),
-	    "BufferedEventCounting::configure",
+	    "BufferedEventCounting::configure()",
 	    err);
   }
   else if (err > 0)
@@ -237,6 +325,7 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
     this->warn_ = this->get_string_error();
     this->warn_occured_ = true;
   }
+  
   //---------------------get task ready to start------------------------------------------------
   try
   {
@@ -252,7 +341,6 @@ void BufferedPositionMeasurement::configure (void) throw (ni660Xsl::DAQException
   }
 
   //std::cout<<<<"BufferedPositionMeasurement::configure->"<<std::endl;
-
 }
 
 }//namespace