optimize left edge finding in autotune

Author: xtaci

autotune.go

@@ -27,20 +27,18 @@ func (tune *autoTune) Sample(bit bool, seq uint32) {
 //          Period
 //  Falling Edge    Rising Edge
 func (tune *autoTune) FindPeriod(bit bool) int {
-	// find left and right edges for a bit
+	// last pulse and initial index setup
 	lastPulse := tune.pulses[0]
 	idx := 1
 
 	// left edge
 	var leftEdge int
 	for ; idx < len(tune.pulses); idx++ {
-		if lastPulse.seq+1 == tune.pulses[idx].seq {
-			if lastPulse.bit != bit && tune.pulses[idx].bit == bit {
+		if lastPulse.bit != bit && tune.pulses[idx].bit == bit { // edge found
+			if lastPulse.seq+1 == tune.pulses[idx].seq { // ensure edge continuity
 				leftEdge = idx
 				break
 			}
-		} else {
-			return -1
 		}
 		lastPulse = tune.pulses[idx]
 	}
@@ -51,8 +49,8 @@ func (tune *autoTune) FindPeriod(bit bool) int {
 	idx = leftEdge + 1
 
 	for ; idx < len(tune.pulses); idx++ {
-		if lastPulse.seq+1 == tune.pulses[idx].seq {
-			if lastPulse.bit == bit && tune.pulses[idx].bit != bit {
+		if lastPulse.seq+1 == tune.pulses[idx].seq { // ensure pulses in this level monotonic
+			if lastPulse.bit == bit && tune.pulses[idx].bit != bit { // edge found
 				rightEdge = idx
 				break
 			}