Some steps towards only publishing measurements when significant changes occur.

src/Data/DataController.cpp

@@ -135,18 +135,52 @@ void DataController::_sample()
         _ui->suspend();
 
         // Take a sample.
+        Measurement m;
         switch (_sampleType)
         {
         case SAMPLE_TEMPERATURE:
-            _temperatureMeasurements.add(_sensors->readTemperature());
+            m = _sensors->readTemperature();
+            _temperatureMeasurements.add(m);
+            if (_temperatureLastPublished.ok && m.ok && _temperatureLastPublished.value != m.value)
+            {
+                if (m.value == _temperatureMeasurements.getAverage().value ||
+                    abs(_temperatureLastPublished.value - m.value) > TEMPERATURE_SIGNIFICANT_CHANGE) {
+                    _publishTemperature();
+                }
+            }
+            else if (_temperatureLastPublished.ok == false && m.ok) {
+                _publishTemperature();
+            }
             _sampleType = SAMPLE_HUMIDITY;
             break;
         case SAMPLE_HUMIDITY:
-            _humidityMeasurements.add(_sensors->readHumidity());
+            m = _sensors->readHumidity();
+            _humidityMeasurements.add(m);
+            if (_humidityLastPublished.ok && m.ok && _humidityLastPublished.value != m.value)
+            {
+                if (m.value == _humidityMeasurements.getAverage().value ||
+                    abs(_humidityLastPublished.value - m.value) > HUMIDITY_SIGNIFICANT_CHANGE) {
+                    _publishHumidity();
+                }
+            }
+            else if (_humidityLastPublished.ok == false && m.ok) {
+                _publishHumidity();
+            }
             _sampleType = SAMPLE_DISTANCE;
             break;
         case SAMPLE_DISTANCE:
-            _distanceMeasurements.add(_sensors->readDistance());
+            m = _sensors->readDistance();
+            _distanceMeasurements.add(m);
+            if (_distanceLastPublished.ok && m.ok && _distanceLastPublished.value != m.value)
+            {
+                if (m.value == _distanceMeasurements.getAverage().value ||
+                    abs(_distanceLastPublished.value - m.value) > DISTANCE_SIGNIFICANT_CHANGE) {
+                    _publishDistance();
+                }
+            }
+            else if (_distanceLastPublished.ok == false && m.ok) {
+                _publishDistance();
+            }
             break;
         }
 
@@ -166,14 +200,36 @@ void DataController::_publish()
     if (_lastPublish == 0 || millis() - _lastPublish > PUBLISH_INTERVAL)
     {
         _lastPublish = millis();
-
-        _mqtt->publish("temperature", _temperatureMeasurements.getLast());
-        _mqtt->publish("temperature/average", _temperatureMeasurements.getAverage());
-        _mqtt->publish("humidity", _humidityMeasurements.getLast());
-        _mqtt->publish("humidity/average", _humidityMeasurements.getAverage());
-        _mqtt->publish("distance", _distanceMeasurements.getLast());
-        _mqtt->publish("distance/average", _distanceMeasurements.getAverage());
-
+        _publishTemperature();
+        _publishHumidity();
+        _publishDistance();
         _ui->led1.dip()->fast();
     }
 }
+
+void DataController::_publishTemperature()
+{
+    auto m = _temperatureMeasurements.getLast();
+    _temperatureLastPublished.ok = m.ok;
+    _temperatureLastPublished.value = m.value;
+    _mqtt->publish("temperature", m);
+    _mqtt->publish("temperature/average", _temperatureMeasurements.getAverage());
+}
+
+void DataController::_publishHumidity()
+{
+    auto m = _humidityMeasurements.getLast();
+    _humidityLastPublished.ok = m.ok;
+    _humidityLastPublished.value = m.value;
+    _mqtt->publish("humidity", _humidityMeasurements.getLast());
+    _mqtt->publish("humidity/average", _humidityMeasurements.getAverage());
+}
+
+void DataController::_publishDistance()
+{
+    auto m = _distanceMeasurements.getLast();
+    _distanceLastPublished.ok = m.ok;
+    _distanceLastPublished.value = m.value;
+    _mqtt->publish("distance", _distanceMeasurements.getLast());
+    _mqtt->publish("distance/average", _distanceMeasurements.getAverage());
+}

src/Data/DataController.h

@@ -10,13 +10,19 @@
 #define SAMPLE_CYCLE_LENGTH 30 // 1 temperature + 1 humidity + 28 distance samples
 
 // Two different values are published per sensor: a recent value and an average
-// value. These definition define the number of measurements to include in the
-// average computation.
-#define TEMPERATURE_AVG_LOOKBACK 10      // making this a 5 minute average
-#define HUMIDITY_AVG_LOOKBACK 10         // making this a 5 minute average
+// value. These definition define the number of recent measurements to include
+// in the average computation.
+#define TEMPERATURE_AVG_LOOKBACK 6       // making this a 3 minute average
+#define HUMIDITY_AVG_LOOKBACK 6          // making this a 3 minute average
 #define DISTANCE_AVG_LOOKBACK 28 * 2 * 5 // making this a 5 minute average
 
-// The minimal interval at which to publish measurements to the MQTT broker.
+// When significant changes occur in the sensor measurements, they are
+// published to MQTT. These definitions specify what is considered significant.
+#define TEMPERATURE_SIGNIFICANT_CHANGE 2 // to dampen flapping between two values on transition
+#define HUMIDITY_SIGNIFICANT_CHANGE 2    // also to dampen flapping behavior.
+#define DISTANCE_SIGNIFICANT_CHANGE 3    // based on the sensor specification of 3mm resolution
+
+// The minimal interval at which to forcibly publish measurements to the MQTT broker.
 // When significant changes occur in the measurements, then these will be published
 // to the MQTT broker at all times, independent from this interval.
 #define PUBLISH_INTERVAL 4000
@@ -57,8 +63,14 @@ private:
     DataController();
     static DataController* _instance;
     Measurements _temperatureMeasurements;
+    Measurement _temperatureLastPublished;
+    void _publishTemperature();
     Measurements _humidityMeasurements;
+    Measurement _humidityLastPublished;
+    void _publishHumidity();
     Measurements _distanceMeasurements;
+    Measurement _distanceLastPublished;
+    void _publishDistance();
     DoughLogger _logger;
     DoughUI* _ui;
     DoughSensors* _sensors;

src/config_local.example.h

@@ -9,7 +9,7 @@
 #define MQTT_PASSWORD "<mqtt password>"
 
 // The prefix to use for the MQTT publishing topic.
-#define MQTT_TOPIC_PREFIX "sensors/doughboy"
+//#define MQTT_TOPIC_PREFIX "sensors/doughboy"
 
 // Define this one to not use the WiFi MAC address as the device ID
 // in the publish topics (sensors/doughboy/<MQTT_DEVICE_ID>/...)