--- a/FXAnalyse.c	Mon Oct 29 14:48:24 2012 +0100
+++ b/FXAnalyse.c	Mon Oct 29 14:48:44 2012 +0100
@@ -1192,44 +1192,45 @@
 					}
 				}
 				
-				// slope measurement 
-				if (SlopeMeasuring == TRUE)
-				{
-					double currentFreq = 0.0;
-					
-					// select reference
-					switch (slopeReference) {
+				// select reference
+				double currentFreq = 0.0;
+				switch (slopeReference) {
 					case SLOPE_REFERENCE_MICROWAVE:
 						currentFreq = Math2;
 						break;
 					case SLOPE_REFERENCE_HG_CAVITY:
 						currentFreq = Ch2 * 1062.5 / 1542.2;
 						break;
-					}
-					
-					// stop slope cancelling if the comb is not locked
-					if (StopSlopeCancellingOnUnlocked
-						& (previousFreq != 0.0)
-						& (fabs(currentFreq - previousFreq) > limitotakoff)) {
-						
-						double frequency = DEDRIFT_DDS_FREQUENCY;
-						if (KeepFrequ)
-							frequency = DDSFox_ReadFreq(&DDS1xAD9956);
+				}
+				
+				// stop slope cancelling if the comb is not locked
+				if (SlopeMeasuring & StopSlopeCancellingOnUnlocked
+					& (previousFreq != 0.0)
+					& (fabs(currentFreq - previousFreq) > limitotakoff)) {
 						
-						if (! KeepSlope)
-							appliedSlope = 0.0;
-						
+					if (! KeepSlope) {
+						appliedSlope = 0.0;
+						DDSFox_SetSweepRate(&DDS1xAD9956, appliedSlope);
 						SetCtrlVal(MainPanel, PANEL_SLOPE_APPLIED, appliedSlope);
-						DDSFox_Set(&DDS1xAD9956, frequency, appliedSlope);
-						
-						measuredSlope = 0.0;
-						SlopeMeasuring = FALSE;
-						SetCtrlVal(MainPanel, PANEL_MEASURE_SLOPE, 0);
+					}
+					if (! KeepFrequ) {
+						DDSFox_Set(&DDS1xAD9956, DEDRIFT_DDS_FREQUENCY, appliedSlope);
 					}
-					
+					measuredSlope = 0.0;
+					SetCtrlVal(MainPanel, PANEL_SLOPE_MEASURED, measuredSlope);
+					SlopeMeasuring = FALSE;
+					SetCtrlVal(MainPanel, PANEL_MEASURE_SLOPE, 0);
+				}
+				
+				// slope measurement 
+				if (SlopeMeasuring)
+				{
 					// update slope measurement
 					Nsamples = Nsamples + 1;
-					measuredSlope = (measuredSlope * (Nsamples - 2) + 6 * (currentFreq - meanFreq) / Nsamples) / (Nsamples + 1);
+					if (Nsamples > 1)
+						measuredSlope = (measuredSlope * (Nsamples - 2) + 6 * (currentFreq - meanFreq) / Nsamples) / (Nsamples + 1);
+					else
+						measuredSlope = 0.0;
 					meanFreq = ((Nsamples - 1) * meanFreq + currentFreq) / Nsamples;
 					previousFreq = currentFreq;
 					// update indicator
@@ -1265,7 +1266,7 @@
 						SetCtrlVal(MainPanel, PANEL_SLOPE_APPLIED, appliedSlope);
 						DDSFox_SetSweepRate(&DDS1xAD9956, appliedSlope);
 						
-						Nsamples = 0.0;
+						Nsamples = 0;
 						meanFreq = 0.0;
 						measuredSlope = 0.0;
 						SlopeMeasuringTimeBegin = utc;
@@ -2187,44 +2188,35 @@
  int  CVICALLBACK CB_MeasureSlope (int panel, int control, int event, 
 		 void *callbackData, int eventData1, int eventData2)
 {
-	double frequency;
-	int active;
-	
-	switch (event)
-	{
+	switch (event) {
 		case EVENT_COMMIT:
 				   
-			GetCtrlVal(panel, control, &active);
-				   
-			if (active) {
+			GetCtrlVal(panel, control, &SlopeMeasuring);
+			if (SlopeMeasuring) {
 				
 				SlopeMeasuringTimeBegin = utc;
-				SlopeMeasuring = TRUE;
+				
+				Nsamples = 0;
 				previousFreq = 0.0;
+				meanFreq = 0.0;
+				measuredSlope = 0.0;
 				
 				Nratio = -1;
+				MoyMath2 = 0.0; 
 				CenterFrequencyCh2ToDetermine = TRUE ;
 				CenterFrequencyCh2 = 0.0;
 				
 			} else {
-				
-				frequency = DEDRIFT_DDS_FREQUENCY;
-				if (KeepFrequ)
-					frequency = DDSFox_ReadFreq(&DDS1xAD9956);
-				
-				if (! KeepSlope)
+				if (! KeepSlope) {
 					appliedSlope = 0.0;
-				
-				SetCtrlVal(panel, PANEL_SLOPE_APPLIED, appliedSlope);
-				DDSFox_Set(&DDS1xAD9956, frequency, appliedSlope);
-				
-				SlopeMeasuring = FALSE; 
-				Nsamples = 0.0;
-				meanFreq = 0.0;
+					DDSFox_SetSweepRate(&DDS1xAD9956, appliedSlope);
+					SetCtrlVal(MainPanel, PANEL_SLOPE_APPLIED, appliedSlope);
+				}
+				if (! KeepFrequ) {
+					DDSFox_Set(&DDS1xAD9956, DEDRIFT_DDS_FREQUENCY, appliedSlope);
+				}
 				measuredSlope = 0.0;
-				MoyMath2 = 0.0; 
-				CenterFrequencyCh2 = 0.0;
-				Nratio = -1;
+				SetCtrlVal(panel, PANEL_SLOPE_MEASURED, measuredSlope);
 			}
 			break;
 	}