Use median calculation instead of average to get valid measurements

apps/widbaroalarm/widget.js

@@ -1,7 +1,7 @@
 (function() {
-  let lastPressure;
+    let medianPressure;
-  let avrPressure;
     let threeHourAvrPressure;
+    let currentPressures = [];
 
     const LOG_FILE = "widbaroalarm.log.json";
     const SETTINGS_FILE = "widbaroalarm.json";
@@ -35,17 +35,13 @@
 
     let alreadyWarned = false;
 
-  function baroHandler(data) {
+    function checkForAlarms(pressure) {
-    if (data === undefined) {
+      if (pressure == undefined || pressure <= 0) return;
-      setTimeout(() => Bangle.getPressure().then(baroHandler), 500);
-    } else {
-      lastPressure = Math.round(data.pressure);
-      if (lastPressure == undefined || lastPressure <= 0) return;
 
       const ts = Math.round(Date.now() / 1000); // seconds
       const d = {
         "ts": ts,
-        "p": lastPressure
+        "p": pressure
       };
 
       // delete entries older than 3h
@@ -63,18 +59,12 @@
       // write data to storage
       storage.writeJSON(LOG_FILE, history3);
 
-      // we need at least three entries for reliable detection
+      if (setting("lowalarm") && pressure <= setting("min")) {
-      if (history3.length >= 3) {
+        showAlarm("Pressure low: " + Math.round(pressure) + " hPa");
-
-        // calculate average of recent three entries
-        avrPressure = (history3[history3.length - 1]["p"] + history3[history3.length - 2]["p"] + history3[history3.length - 3]["p"]) / 3;
-
-        if (setting("lowalarm") && avrPressure <= setting("min")) {
-          showAlarm("Pressure low: " + Math.round(avrPressure) + " hPa");
         alreadyWarned = true;
       }
-        if (setting("highalarm") && avrPressure >= setting("max")) {
+      if (setting("highalarm") && pressure >= setting("max")) {
-          showAlarm("Pressure high: " + Math.round(avrPressure) + " hPa");
+        showAlarm("Pressure high: " + Math.round(pressure) + " hPa");
         alreadyWarned = true;
       }
 
@@ -88,27 +78,24 @@
             return;
           }
 
-            // Average of oldest three entries
+          // Get oldest entry:
-            const oldestAvgPressure = (history3[0]["p"] + history3[1]["p"] + history3[2]["p"]) / 3;
+          const oldestPressure = history3[0]["p"];
-            if (oldestAvgPressure != undefined && oldestAvgPressure > 0) {
+          if (oldestPressure != undefined && oldestPressure > 0) {
-              const diff = oldestAvgPressure - avrPressure;
+            const diff = oldestPressure - pressure;
 
             // drop alarm
-              if (drop3halarm > 0 && oldestAvgPressure > avrPressure) {
+            if (drop3halarm > 0 && oldestPressure > pressure) {
               if (Math.abs(diff) > drop3halarm) {
                 showAlarm((Math.round(Math.abs(diff) * 10) / 10) + " hPa/3h from " +
-                    Math.round(oldestAvgPressure) + " to " + Math.round(avrPressure) + " hPa",
+                  Math.round(oldestPressure) + " to " + Math.round(pressure) + " hPa", "Pressure drop");
-                    "Pressure drop"));
             }
           }
 
           // raise alarm
-              if (raise3halarm > 0 && oldestAvgPressure < avrPressure) {
+          if (raise3halarm > 0 && oldestPressure < pressure) {
             if (Math.abs(diff) > raise3halarm) {
               showAlarm((Math.round(Math.abs(diff) * 10) / 10) + " hPa/3h from " +
-                    Math.round(oldestAvgPressure) + " to " + Math.round(avrPressure) + " hPa",
+                Math.round(oldestPressure) + " to " + Math.round(pressure) + " hPa", "Pressure raise");
-                    "Pressure raise"));
-                }
           }
         }
       }
@@ -122,10 +109,45 @@
   }
   threeHourAvrPressure = sum / history3.length;
 }
+
+
+
+function baroHandler(data) {
+  if (data) {
+    const pressure = Math.round(data.pressure);
+    if (pressure == undefined || pressure <= 0) return;
+    currentPressures.push(pressure);
+  }
 }
 
+/*
+ turn on barometer power
+ take 5 measurements
+ sort the results
+ take the middle one (median)
+ turn off barometer power
+*/
 function check() {
+  Bangle.setBarometerPower(true, "widbaroalarm");
+  setTimeout(function() {
+    currentPressures = [];
+
     Bangle.getPressure().then(baroHandler);
+    Bangle.getPressure().then(baroHandler);
+    Bangle.getPressure().then(baroHandler);
+    Bangle.getPressure().then(baroHandler);
+    Bangle.getPressure().then(baroHandler);
+
+    setTimeout(function() {
+      Bangle.setBarometerPower(false, "widbaroalarm");
+
+      currentPressures.sort();
+
+      // take median value
+      medianPressure = currentPressures[3];
+      checkForAlarms(medianPressure);
+    }, 1000);
+  }, 500);
 }
 
 function reload() {
@@ -134,9 +156,9 @@
 
 function draw() {
   g.reset();
-    if (setting("show") && lastPressure != undefined) {
+  if (setting("show") && medianPressure != undefined) {
     g.setFont("6x8", 1).setFontAlign(1, 0);
-      g.drawString(Math.round(lastPressure), this.x + 24, this.y + 6);
+    g.drawString(Math.round(medianPressure), this.x + 24, this.y + 6);
     if (threeHourAvrPressure != undefined && threeHourAvrPressure > 0) {
       g.drawString(Math.round(threeHourAvrPressure), this.x + 24, this.y + 6 + 10);
     }
@@ -158,6 +180,6 @@
 if (interval > 0) {
   setInterval(check, interval * 60000);
 }
-  }, 10000);
+}, 5000);
 
 })();