added code to transmit sample frequency along with sample data (more compatibility between arduino and PC, and possibility to change sampling rate at run-time)

OneWireIO.ino

@@ -7,6 +7,7 @@
 
 // how many samples we want to skip between two samples we keep (can be used to lower the sampling frequency)
 #define SkipSamples 0
+byte regularEncodedFrequency;
 
 const int BufferSize = 512;
 byte buffer1[BufferSize];
@@ -38,11 +39,19 @@ void setup()
     ADMUX |= (1 << REFS0); //set reference voltage
     ADMUX |= (1 << ADLAR); //left align the ADC value- so we can read highest 8 bits from ADCH register only
     
-    ADCSRA |= (1 << ADPS2) | (0 << ADPS1) | (1 << ADPS0); //set ADC clock with 32 prescaler- 16mHz/32=500KHz ; 13 cycles for a conversion which means 38000 samples per second
+	int ADPS = (1 << ADPS2) | (0 << ADPS1) | (1 << ADPS0);
+    ADCSRA |= ADPS; //set ADC clock with 32 prescaler- 16mHz/32=500KHz ; 13 cycles for a conversion which means 38000 samples per second
     ADCSRA |= (1 << ADATE); //enabble auto trigger
     ADCSRA |= (1 << ADIE); //enable interrupts when measurement complete
     ADCSRA |= (1 << ADEN); //enable ADC
     ADCSRA |= (1 << ADSC); //start ADC measurements
+
+	regularEncodedFrequency = (byte)ADPS;
+	byte skipSamples = 0;
+	#if SkipSamples > 0
+	skipSamples = SkipSamples;
+	#endif
+	regularEncodedFrequency |= skipSamples << 3;
     
     sei();//enable interrupts
     
@@ -63,7 +72,9 @@ void loop()
     digitalWrite(LEDPin, LOW);
     
     //Serial.write(currentBuffer, currentBufferSize);
-    oscilloscope.write(currentBuffer, currentBufferSize, currentBufferStartTime);
+    oscilloscope.beginWrite(currentBufferSize + 1, currentBufferStartTime);
+    oscilloscope.continueWrite(&regularEncodedFrequency, 1);
+    oscilloscope.continueWrite(currentBuffer, currentBufferSize);
 }
 
 ISR(ADC_vect) {//when new ADC value ready

SerialChannel.cpp

@@ -23,16 +23,26 @@ SerialChannel::SerialChannel(const char* name_)
 
 void SerialChannel::write(byte* data, short byteCount, unsigned long time)
 {
-    if (time == (unsigned long)-1)
-        time = micros();
-        
-    handleConnection();
+	beginWrite(byteCount, time);
+	continueWrite(data, byteCount);
+}
+
+void SerialChannel::beginWrite(short byteCount, unsigned long time)
+{
+	if (time == (unsigned long)-1)
+		time = micros();
+
+	handleConnection();
 
-    Serial.write("START");
-    Serial.write(id);
-    writeULong(time);
-    writeShort(byteCount);
-    Serial.write(data, byteCount);
+	Serial.write("START");
+	Serial.write(id);
+	writeULong(time);
+	writeShort(byteCount);
+}
+
+void SerialChannel::continueWrite(byte* data, short byteCount)
+{
+	Serial.write(data, byteCount);
 }
 
 void SerialChannel::write(const char* text, unsigned long time)

SerialChannel.h

@@ -17,6 +17,9 @@ public:
     void write(byte* data, short byteCount, unsigned long time = (unsigned long)-1);
     
     void write(const char* text, unsigned long time = (unsigned long)-1);
+
+	void beginWrite(short byteCount, unsigned long time = (unsigned long)-1);
+	void continueWrite(byte* data, short byteCount);
     
 private:
     void handleConnection();

SerialMonitor/SerialMonitor/App.xaml.cs

@@ -85,7 +85,8 @@ namespace SerialMonitor
                     MainWindowContext.Get.WriteLine(text);
                     break;
                 case "oscilloscope":
-                    MainWindowContext.Get.AddSequence(message.SendTime, message.Data);
+                    byte frequency = message.Data[0];
+                    MainWindowContext.Get.AddSequence(message.SendTime, frequency, message.Data.Skip(1).ToArray());
                     break;
             }
         }

SerialMonitor/SerialMonitor/MainWindowContext.cs

@@ -35,13 +35,13 @@ namespace SerialMonitor
             OnPropertyChanged("ConsoleText");
         }
 
-        public double SampleDelay { get { return 0.000026; } }
         public int MaxSequenceSize { get { return 2048; } }
 
         private class Sequence
         {
-            public ulong StartTime { get; set; }
+            public ulong StartTime { get; set; } // time in microseconds of the first sample
             public byte[] Data { get; set; }
+            public double Frequency { get; set; } // sampling rate (in samples per second)
 
             public class Comparer : IComparer<Sequence>
             {
@@ -67,7 +67,8 @@ namespace SerialMonitor
                 foreach (var sequence in Sequences)
                 {
                     double seqStartTime = (double)sequence.StartTime/1000000.0;
-                    if (seqStartTime + (double)sequence.Data.Length * SampleDelay > ViewportStartTime && seqStartTime < ViewportStartTime + ViewportTimeWidth)
+                    double sampleDelay = 1.0 / sequence.Frequency;
+                    if (seqStartTime + (double)sequence.Data.Length * sampleDelay > ViewportStartTime && seqStartTime < ViewportStartTime + ViewportTimeWidth)
                     {
                         foreach (var line in ConvertToLines(sequence))
                             yield return line;
@@ -82,6 +83,7 @@ namespace SerialMonitor
             double scale = viewportWidth / ViewportTimeWidth; // in pixels per second
 
             ulong displayStartTime = (ulong)(viewportStartTime_ * 1000000.0);
+            double sampleDelay = 1.0 / sequence.Frequency;
 
             double pos = ((double)sequence.StartTime - (double)displayStartTime) / 1000000.0 * scale;
             if (pos > 1000)
@@ -94,7 +96,7 @@ namespace SerialMonitor
             for (int idx = 1; idx < sequence.Data.Length; ++idx)
             {
                 byte value = sequence.Data[idx];
-                pos += SampleDelay * scale;
+                pos += sampleDelay * scale;
                 if (value > maxValue) maxValue = value;
                 if (value < minValue) minValue = value;
 
@@ -110,7 +112,7 @@ namespace SerialMonitor
                     prevPos = pos;
                     line.X2 = pos;
 
-                    double time = (double)sequence.StartTime / 1000000.0 + (double)idx * SampleDelay;
+                    double time = (double)sequence.StartTime / 1000000.0 + (double)idx * sampleDelay;
                     double lastHeight = ValueToHeight(time, value);
 
                     if (idx == prevIdx + 1)
@@ -142,10 +144,20 @@ namespace SerialMonitor
             }
         }
 
-        public void AddSequence(ulong startTime, byte[] data)
+        public void AddSequence(ulong startTime, byte frequency, byte[] data)
         {
             // TODO: merge sequences if total size is lower than MaxSequenceSize
-            var sequence = new Sequence { StartTime = startTime, Data = data };
+            double cpuClock = 16000000.0;
+            int adsp0 = (frequency & (1 << 0)) != 0 ? 1 : 0;
+            int adsp1 = (frequency & (1 << 1)) != 0 ? 1 : 0;
+            int adsp2 = (frequency & (1 << 2)) != 0 ? 1 : 0;
+            int skipBit0 = (frequency & (1 << 3)) != 0 ? 1 : 0;
+            int skipBit1 = (frequency & (1 << 4)) != 0 ? 1 : 0;
+            int skipBit2 = (frequency & (1 << 5)) != 0 ? 1 : 0;
+            int adcDivider =  1 << Math.Max(1, adsp0 + adsp1*2 + adsp2*4);
+            int skip = skipBit0 + skipBit1 * 2 + skipBit2 * 4;
+            double freq = cpuClock / (double)adcDivider / 13.0 / (double)(1 + skip);
+            var sequence = new Sequence { StartTime = startTime, Frequency = freq, Data = data };
             Sequences.Add(sequence);
             OnPropertyChanged("Oscilloscope");
             OnPropertyChanged("MinTime");