--- a/FXAnalyse.c	Fri May 02 16:33:24 2014 +0200
+++ b/FXAnalyse.c	Thu Sep 18 18:01:38 2014 +0200
@@ -260,11 +260,52 @@
 double f_beat_plus, f_beat_minus;
 double N_measured; 
 
-double Frequencystep1=10000.0, tbegin1=0.0, Frepbefore1=0.0, Frequency1=0.0;
-double Frequencystep2=10.0, tbegin2=0.0, Frepbefore2=0.0, Ch2before=0.0, Frequency2=0.0;
-double Frequencystep3=100000.0, tbegin3=0.0, Frepbefore3=0.0, Frequency3=0.0;
+// Beatnote sign determination is done stepping the repetition rate by
+// stepping the comb phase-lock offset frequency f_lock generated by
+// DDS1.  A lock frequency step delta_f_lock determines a change in the
+// repetition rate given by:
+//
+//   abs(delta_f_rep) = Ndiv * delta_f_lock / N1
+// 
+// where Ndiv = 8 and N1 ~= 8 x 10^5 obtaining that
+// 
+//   abs(delta_f_rep) ~= delta_f_lock / 10^5
+//
+// For the determination of the comb locking beatnote sign we detect
+// the sign of delta_f_rep caused by a positive delta_f_lock. f_rep is
+// measured should be small enough to do not exceed the 200x PLL
+// bandwidth but still be clearly identified.
+// 
+// For the optical beatnotes we detect the sign of delta_f_beat caused
+// by a positive delta_f_lock thus we need to take into account the
+// sign of the comb locking beatnote.  The optical beatnote frequency
+// change is given by
+// 
+//   abs(delta_f_beat) = abs(delta_f_rep) * Nx
+// 
+// where Nx ~= 10^6 obtaining that
+// 
+//   abs(delta_f_beat) ~= delta_f_lock * 10
+//
+// this need to do not exceed the beatnote filters bandwidth.  Given
+// those contraints the following f_lock steps are chosen:
 
-int Getsign1=FALSE,Getsign2=FALSE,Getsign3=FALSE;
+double f_lock_step_1 = 10000.0;
+double f_lock_step_2 = 10.0;
+double f_lock_step_3 = 10.0;
+
+struct beatsign {
+	int measure;		// which beatnote sign is being measured
+	double f0_DDS1;		// DDS1 frequency before stepping
+	double t0;			// measurement start time
+	double f_rep_zero;	// repetition rate before stepping
+	double f_beat_zero;	// beatnote frequwncy before stepping
+};
+
+struct beatsign beatsign = {
+	.measure = 0,
+};
+
 
 struct stat stat_math1, stat_ch2, stat_ch3, freq;
 struct rollmean rollmean_ch1, rollmean_ch2, rollmean_ch3, rollmean_ch4;
@@ -1206,47 +1247,45 @@
 						break;
 				}
 				
-				// beatnote sign determination
-				
-				if (Getsign1 == TRUE) {
-					if (utc > tbegin1+2) {
-						if (Math1 > Frepbefore1)
-							Sign1 = -1.0;
-						else
-							Sign1 = +1.0;
-						ad9912_set_frequency_w(&ad9912, 0, Frequency1);
-						Getsign1 = FALSE;
+				// beatnote sign determination				
+				if ((beatsign.measure) && 
+				    (utc > beatsign.t0 + 2.0)) {
+
+					int f_beat_sign, f_rep_sign = 0; 
+					
+					switch (beatsign.measure) {
+					case LO:
+						f_rep_sign = (Math1 > beatsign.f_rep_zero) ? -1 : 1;
+						Sign1 = f_rep_sign;
 						SetCtrlVal(MainPanel, PANEL_SIGN1, Sign1);
+						break;
+					case HG:
+						f_rep_sign = (Math1 > beatsign.f_rep_zero) ? -1 : 1;
+						f_beat_sign = (Ch2 > beatsign.f_beat_zero) ? -1 : 1;
+						Sign2 = f_rep_sign * f_beat_sign;
+						SetCtrlVal(MainPanel, PANEL_SIGN2, Sign2);
+						break;
+					case SR:
+						f_rep_sign = (Math1 > beatsign.f_rep_zero) ? -1 : 1;
+						f_beat_sign = (Ch3 > beatsign.f_beat_zero) ? -1 : 1;
+						Sign3 = f_rep_sign * f_beat_sign;
+						SetCtrlVal(MainPanel, PANEL_SIGN3, Sign3);
+						break;
 					}
-				}
-				if (Getsign2 == TRUE) {
-					if (utc > tbegin2+2){
-						if (Math1 > Frepbefore2) { 
-							if (Ch2 > Ch2before)
-								Sign2 = +1.0;
-							else
-								Sign2 = -1.0;
-						} else {
-							if (Ch2 > Ch2before)
-								Sign2 = -1.0;
-							else 
-								Sign2 = +1.0;
-						}
-						ad9912_set_frequency_w(&ad9912, 0, Frequency2);
-						Getsign2 = FALSE;
-						SetCtrlVal(MainPanel, PANEL_SIGN2, Sign2);
-					}
-				}
-				if (Getsign3 == TRUE) {
-					if (utc > tbegin3+2){
-						if (Ch3 > Frepbefore3)
-							Sign3 = -1.0;
-						else
-							Sign3 = +1.0;
-						ad9912_set_frequency_w(&ad9912, 0, Frequency3);
-						Getsign3 = FALSE;
-						SetCtrlVal(MainPanel, PANEL_SIGN3, Sign3);
-					}
+
+					// back to original repetition rate
+					ad9912_set_frequency_w(&ad9912, 0, beatsign.f0_DDS1);
+					SetCtrlVal(MainPanel, PANEL_DDS1, ad9912.frequency[0]);
+
+					// measurement done
+					beatsign.measure = 0;
+						
+					// in the case of the optical beatnotes sign measurement
+					// we induce fairly small steps in f_rep therefore it is
+					// good to check that we get the sign of the comb locking 
+					// beatnote right in those cases
+					if (f_rep_sign != Sign1)
+						logmessage(ERROR, "merasured f_rep_sign does not agree with previous determination!");
 				}
 				
 				// select reference
@@ -1693,37 +1732,36 @@
 int  CVICALLBACK CB_OnFindSign (int panel, int control, int event, 
 		void *callbackData, int eventData1, int eventData2)
 {
+	double step = 0.0;
 	switch (event)
 	{
 		case EVENT_COMMIT:
-			switch (control)
-			{
-				case PANEL_FINDSIGN1:
-					tbegin1 = utc;
-					Frepbefore1 = Math1;
-					GetCtrlVal(MainPanel, PANEL_DDS1, &Frequency1) ;
-					SetCtrlVal(MainPanel, PANEL_DDS1, Frequency1+Frequencystep1) ;  
-					ad9912_set_frequency_w(&ad9912, 0, Frequency1+Frequencystep1);
-					Getsign1 = TRUE;
+			switch (control) {
+			        case PANEL_FINDSIGN1:
+					beatsign.measure = LO;
+					beatsign.f_beat_zero = 0.0;
+					step = f_lock_step_1;
 					break;
 				case PANEL_FINDSIGN2:
-					tbegin2 = utc;
-					Frepbefore2 = Math1;
-					Ch2before = Ch2;
-					GetCtrlVal(MainPanel, PANEL_DDS1, &Frequency2) ;
-					SetCtrlVal(MainPanel, PANEL_DDS1, Frequency2+Frequencystep2) ;
-					ad9912_set_frequency_w(&ad9912, 0, Frequency2+Frequencystep2);
-					Getsign2 = TRUE;
+					beatsign.measure = HG;
+					beatsign.f_beat_zero = Ch2;
+					step = f_lock_step_2;
 					break;
 				case PANEL_FINDSIGN3:
-					tbegin3 = utc;
-					Frepbefore3 = Math1;
-					GetCtrlVal(MainPanel, PANEL_DDS1, &Frequency3) ;
-					SetCtrlVal(MainPanel, PANEL_DDS1, Frequency3+Frequencystep3) ; 
-					ad9912_set_frequency_w(&ad9912, 0, Frequency3+Frequencystep3);
-					Getsign3 = TRUE;
+					beatsign.measure = SR;
+					beatsign.f_beat_zero = Ch3;
+					step = f_lock_step_3;
 					break;
 			}
+
+			beatsign.t0 = utc;
+			beatsign.f_rep_zero = Math1;
+
+			// step the repetition rate
+			beatsign.f0_DDS1 = ad9912.frequency[0];
+			ad9912_set_frequency_w(&ad9912, 0, beatsign.f0_DDS1 + step);
+			SetCtrlVal(MainPanel, PANEL_DDS1, ad9912.frequency[0]);
+
 			break;
 	}
 	return 0;