Get curve value without expo applied

Add the facility to get the curve without the expo applied, better for
the spectrum analyser (maybe)?

Also added frequency labels to the analyser.

js/expo.js

@@ -7,12 +7,16 @@
  */
 function ExpoCurve(offset, power, inputRange, outputRange, steps) {
     var
-        curve, inputScale;
+        curve, inputScale, rawInputScale;
 
     function lookupStraightLine(input) {
         return (input + offset) * inputScale;
     }
 
+    this.lookupRaw = function(input) {
+        return (input + offset) * rawInputScale;
+    }
+
     /**
      * An approximation of lookupMathPow by precomputing several expo curve points and interpolating between those
      * points using straight line interpolation.
@@ -58,6 +62,8 @@ function ExpoCurve(offset, power, inputRange, outputRange, steps) {
         return result;
     }
 
+    rawInputScale = outputRange / inputRange;
+
     // If steps argument isn't supplied, use a reasonable default
     if (steps === undefined) {
         steps = 12;

js/graph_spectrum.js

@@ -53,7 +53,7 @@ function dataLoad(chunks, startFrameIndex, fieldIndex, curve, buffer) {
             var chunk = chunks[chunkIndex];
             for (; frameIndex < chunk.frames.length; frameIndex++) {
             	var fieldValue = chunk.frames[frameIndex][fieldIndex];
-                bufferData[i++] = (curve.lookup(fieldValue));
+                bufferData[i++] = (curve.lookupRaw(fieldValue));
 
                 if (i >= buffer.length)
                     break dataCollectionLoop;
@@ -91,7 +91,7 @@ function draw() {
       canvasCtx.fillStyle = 'rgba(255, 255, 255, .25)'; /* white */
       canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
 
-      var barWidth = (WIDTH / PLOTTED_BUFFER_LENGTH);// * 2.5;
+      var barWidth = (WIDTH / PLOTTED_BUFFER_LENGTH) - 1;// * 2.5;
       var barHeight;
       var x = 0;
 
@@ -101,17 +101,43 @@ function draw() {
         canvasCtx.fillStyle = 'rgba(0,255,0,0.3)'; /* green */
         canvasCtx.fillRect(x,HEIGHT-barHeight,barWidth,barHeight);
 
-        x += barWidth;
+        x += barWidth + 1;
       }
-      drawAxisLabel('#' + leftPad(audioIterations, "0", 7), WIDTH - 8, HEIGHT - 10);
+      drawGridLines(options.analyserSampleRate, LEFT, TOP, WIDTH, HEIGHT);
+      drawAxisLabel('#' + leftPad(audioIterations, "0", 7), WIDTH - 8, HEIGHT - 10, 'right');
 	  canvasCtx.restore();
 	}
 
+function drawGridLines(sampleRate, LEFT, TOP, WIDTH, HEIGHT) {
+
+	var ticks = 5;
+	var frequencyInterval = (sampleRate / ticks) / 4;
+	var frequency = 0;
+
+	for(var i=0; i<=ticks; i++) {
+		    canvasCtx.beginPath();
+            canvasCtx.lineWidth = 1;
+            canvasCtx.strokeStyle = "rgba(255,255,255,0.25)";
+
+            canvasCtx.moveTo(i * (WIDTH / ticks), 0);
+            canvasCtx.lineTo(i * (WIDTH / ticks), HEIGHT);
+
+            canvasCtx.stroke();
+            drawAxisLabel((frequency)+"Hz", i * (WIDTH / ticks), HEIGHT * 1.05, 'center');
+			frequency += frequencyInterval;
+	}	
+}
 
-function drawAxisLabel(axisLabel, X, Y) {
+function drawAxisLabel(axisLabel, X, Y, align) {
         canvasCtx.font = drawingParams.fontSizeFrameLabel + "pt " + DEFAULT_FONT_FACE;
         canvasCtx.fillStyle = "rgba(255,255,255,0.9)";
-        canvasCtx.textAlign = 'right';
+		if(align) {
+			 canvasCtx.textAlign = align;
+			 } else 
+			 {
+			 canvasCtx.textAlign = 'center';
+			 }
+
 
         canvasCtx.fillText(axisLabel, X, Y);
     }

js/grapher.js

@@ -53,7 +53,8 @@ function FlightLogGrapher(flightLog, graphConfig, canvas, craftCanvas, options)
         defaultOptions = {
             gapless:false,
             drawCraft:"3D", drawPidTable:true, drawSticks:true, drawTime:true,
-            drawAnalyser:true,    // add an analyser option
+            drawAnalyser:true,              // add an analyser option
+            analyserSampleRate:2000/*Hz*/,  // the loop time for the log
             eraseBackground: true // Set to false if you want the graph to draw on top of an existing canvas image
         },