Update lib.js to save averaged HR instead of last HR

Previous version saved the last sent HR reading when saving to CSV. Updated to maintain an average of all HR readings during each recording interval (only readings with confidence > 80), and save this instead. If no readings pass confidence threshold, the reading with the highest confidence is saved.

Author: ruvilonix

apps/recorder/lib.js

@@ -61,18 +61,45 @@ exports.getRecorders = function() {
       };
     },
     hrm:function() {
-      var bpm = "", bpmConfidence = "", src="";
+      const CONFIDENCE_THRESHOLD = 80;
+      var avgBpm = 0, avgBpmConfidence = 0, src="", nAvgReadings=0, lowConfBpm=null, lowConfBpmConfidence=-1;
+
       function onHRM(h) {
-        bpmConfidence = h.confidence;
-        bpm = h.bpm;
+        let newBpmConfidence = h.confidence;
+        let newBpm = h.bpm;
         src = h.src;
+
+        if (newBpmConfidence >= CONFIDENCE_THRESHOLD){
+          nAvgReadings++;
+          avgBpm = avgBpm + (newBpm-avgBpm)/nAvgReadings;
+          avgBpmConfidence = avgBpmConfidence + (newBpmConfidence-avgBpmConfidence)/nAvgReadings;
+
+        } else if (newBpmConfidence > lowConfBpmConfidence) {
+          lowConfBpmConfidence = newBpmConfidence;
+          lowConfBpm = newBpm;
+        }
       }
+
       return {
         name : "HR",
         fields : ["Heartrate", "Confidence", "Source"],
         getValues : () => {
-          var r = [bpm,bpmConfidence,src];
-          bpm = ""; bpmConfidence = ""; src="";
+          let r;
+
+          if (nAvgReadings === 0) {
+            if (lowConfBpm === null) r = ["","",""];
+            else r = [lowConfBpm,lowConfBpmConfidence,src];
+          } else {
+            r = [Math.round(avgBpm),Math.round(avgBpmConfidence),src];
+          }
+
+          avgBpm = 0; 
+          avgBpmConfidence = 0; 
+          nAvgReadings=0; 
+          lowConfBpm=null; 
+          lowConfBpmConfidence=-1;
+          src=""; 
+
           return r;
         },
         start : () => {
@@ -384,4 +411,4 @@ exports.isRecording = function() {
   return !!writeSetup;
 };
 
-exports.reload({noUpdateWidget:true});
+exports.reload({noUpdateWidget:true});