diff --git a/src/demoreader.cpp b/src/demoreader.cpp
--- a/src/demoreader.cpp
+++ b/src/demoreader.cpp
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2016 Hasan Yavuz Özderya
+  Copyright © 2017 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -25,8 +25,9 @@
 #define M_PI 3.14159265358979323846
 #endif
 
-DemoReader::DemoReader(QIODevice* device, ChannelManager* channelMan, QObject *parent) :
-    AbstractReader(device, channelMan, parent)
+DemoReader::DemoReader(QIODevice* device, ChannelManager* channelMan,
+                       DataRecorder* recorder, QObject* parent) :
+    AbstractReader(device, channelMan, recorder, parent)
 {
     paused = false;
     _numOfChannels = 1;
@@ -76,13 +77,13 @@ void DemoReader::demoTimerTimeout()
 
     if (!paused)
     {
+        double* samples = new double[_numOfChannels];
         for (unsigned ci = 0; ci < _numOfChannels; ci++)
         {
             // we are calculating the fourier components of square wave
-            double value = 4*sin(2*M_PI*double((ci+1)*count)/period)/((2*(ci+1))*M_PI);
-            _channelMan->addChannelData(ci, &value, 1);
-            sampleCount++;
+            samples[ci] = 4*sin(2*M_PI*double((ci+1)*count)/period)/((2*(ci+1))*M_PI);
         }
-        emit dataAdded();
+        addData(samples, _numOfChannels);
+        delete[] samples;
     }
 }