Feature: know and use SoC precision

the Victron SmartShunt communicates the SoC value in permille. this
should be displayed in the web UI accordingly. this is a good excuse to
fully move ownership of the SoC value to the BatteryStats base class and
add a precision indicator variable. this is required to be set each time
a derived class (a battery provider) wants to update the SoC value. the
precision is then used when populating the JSON data for the web UI
(live view).

related to #573.

include/BatteryStats.h

@@ -17,7 +17,7 @@ class BatteryStats {
         uint32_t getAgeSeconds() const { return (millis() - _lastUpdate) / 1000; }
         bool updateAvailable(uint32_t since) const { return _lastUpdate > since; }
 
-        uint8_t getSoC() const { return _SoC; }
+        uint8_t getSoC() const { return _soc; }
         uint32_t getSoCAgeSeconds() const { return (millis() - _lastUpdateSoC) / 1000; }
 
         float getVoltage() const { return _voltage; }
@@ -36,18 +36,26 @@ class BatteryStats {
 
     protected:
         virtual void mqttPublish() const;
+
+        void setSoC(float soc, uint8_t precision, uint32_t timestamp) {
+            _soc = soc;
+            _socPrecision = precision;
+            _lastUpdateSoC = timestamp;
+        }
+
         void setVoltage(float voltage, uint32_t timestamp) {
             _voltage = voltage;
             _lastUpdateVoltage = timestamp;
         }
 
         String _manufacturer = "unknown";
-        uint8_t _SoC = 0;
-        uint32_t _lastUpdateSoC = 0;
         uint32_t _lastUpdate = 0;
 
     private:
         uint32_t _lastMqttPublish = 0;
+        float _soc = 0;
+        uint8_t _socPrecision = 0; // decimal places
+        uint32_t _lastUpdateSoC = 0;
         float _voltage = 0; // total battery pack voltage
         uint32_t _lastUpdateVoltage = 0;
 };
@@ -61,7 +69,6 @@ class PylontechBatteryStats : public BatteryStats {
 
     private:
         void setManufacturer(String&& m) { _manufacturer = std::move(m); }
-        void setSoC(uint8_t SoC) { _SoC = SoC; _lastUpdateSoC = millis(); }
         void setLastUpdate(uint32_t ts) { _lastUpdate = ts; }
 
         float _chargeVoltage;
@@ -155,9 +162,7 @@ class MqttBatteryStats : public BatteryStats {
         // we do NOT publish the same data under a different topic.
         void mqttPublish() const final { }
 
-        // the SoC is the only interesting value in this case, which is already
+        // if the voltage is subscribed to at all, it alone does not warrant a
-        // displayed at the top of the live view. do not generate a card.
+        // card in the live view, since the SoC is already displayed at the top
         void getLiveViewData(JsonVariant& root) const final { }
-
-        void setSoC(uint8_t SoC) { _SoC = SoC; _lastUpdateSoC = _lastUpdate = millis(); }
 };

src/BatteryStats.cpp

@@ -56,7 +56,7 @@ void BatteryStats::getLiveViewData(JsonVariant& root) const
     root[F("manufacturer")] = _manufacturer;
     root[F("data_age")] = getAgeSeconds();
 
-    addLiveViewValue(root, "SoC", _SoC, "%", 0);
+    addLiveViewValue(root, "SoC", _soc, "%", _socPrecision);
     addLiveViewValue(root, "voltage", _voltage, "V", 2);
 }
 
@@ -212,7 +212,7 @@ void BatteryStats::mqttPublish() const
 {
     MqttSettings.publish(F("battery/manufacturer"), _manufacturer);
     MqttSettings.publish(F("battery/dataAge"), String(getAgeSeconds()));
-    MqttSettings.publish(F("battery/stateOfCharge"), String(_SoC));
+    MqttSettings.publish(F("battery/stateOfCharge"), String(_soc));
     MqttSettings.publish(F("battery/voltage"), String(_voltage));
 }
 
@@ -334,9 +334,9 @@ void JkBmsBatteryStats::updateFrom(JkBms::DataPointContainer const& dp)
 
     auto oSoCValue = dp.get<Label::BatterySoCPercent>();
     if (oSoCValue.has_value()) {
-        _SoC = *oSoCValue;
         auto oSoCDataPoint = dp.getDataPointFor<Label::BatterySoCPercent>();
-        _lastUpdateSoC = oSoCDataPoint->getTimestamp();
+        BatteryStats::setSoC(*oSoCValue, 0/*precision*/,
+                oSoCDataPoint->getTimestamp());
     }
 
     auto oVoltage = dp.get<Label::BatteryVoltageMilliVolt>();
@@ -367,8 +367,8 @@ void JkBmsBatteryStats::updateFrom(JkBms::DataPointContainer const& dp)
 
 void VictronSmartShuntStats::updateFrom(VeDirectShuntController::veShuntStruct const& shuntData) {
     BatteryStats::setVoltage(shuntData.V, millis());
+    BatteryStats::setSoC(static_cast<float>(shuntData.SOC) / 10, 1/*precision*/, millis());
 
-    _SoC = shuntData.SOC / 10;
     _current = shuntData.I;
     _modelName = shuntData.getPidAsString().data();
     _chargeCycles = shuntData.H4;
@@ -387,7 +387,6 @@ void VictronSmartShuntStats::updateFrom(VeDirectShuntController::veShuntStruct c
     _alarmHighTemperature = shuntData.AR & 64;
 
     _lastUpdate = VeDirectShunt.getLastUpdate();
-    _lastUpdateSoC = VeDirectShunt.getLastUpdate();
 }
 
 void VictronSmartShuntStats::getLiveViewData(JsonVariant& root) const {

src/MqttBattery.cpp

@@ -82,7 +82,7 @@ void MqttBattery::onMqttMessageSoC(espMqttClientTypes::MessageProperties const&
         return;
     }
 
-    _stats->setSoC(static_cast<uint8_t>(*soc));
+    _stats->setSoC(*soc, 0/*precision*/, millis());
 
     if (_verboseLogging) {
         MessageOutput.printf("MqttBattery: Updated SoC to %d from '%s'\r\n",

src/PylontechCanReceiver.cpp

@@ -136,7 +136,7 @@ void PylontechCanReceiver::loop()
         }
 
         case 0x355: {
-            _stats->setSoC(static_cast<uint8_t>(this->readUnsignedInt16(rx_message.data)));
+            _stats->setSoC(static_cast<uint8_t>(this->readUnsignedInt16(rx_message.data)), 0/*precision*/, millis());
             _stats->_stateOfHealth = this->readUnsignedInt16(rx_message.data + 2);
 
             if (_verboseLogging) {
@@ -282,7 +282,7 @@ void PylontechCanReceiver::dummyData()
     };
 
     _stats->setManufacturer("Pylontech US3000C");
-    _stats->setSoC(42);
+    _stats->setSoC(42, 0/*precision*/, millis());
     _stats->_chargeVoltage = dummyFloat(50);
     _stats->_chargeCurrentLimitation = dummyFloat(33);
     _stats->_dischargeCurrentLimitation = dummyFloat(12);