JK BMS: Support for MQTT (#432)

* JK BMS: avoid trailing whitespace in debug output

* JK BMS: publish data points through MQTT

* JK BMS: updateFrom: skip data points with equal value

this changes the interpretation of the timestamp in data containers that
are merely updated from other data containers: this is the oldest
timestamp known where the value was as recorded by the data point in its
respective container.

the data container constructed from an answer will -- naturally -- have
the timetamps of its data points set to the time they were constructed.

* JK BMS: only publish changed values to MQTT broker

all values are still published once every minute if the MQTT retain flag
is NOT set. otherwise, the constant values are only published once on
startup.

include/BatteryStats.h

@@ -95,4 +95,6 @@ class JkBmsBatteryStats : public BatteryStats {
 
     private:
         JkBms::DataPointContainer _dataPoints;
+        mutable uint32_t _lastMqttPublish = 0;
+        mutable uint32_t _lastFullMqttPublish = 0;
 };

include/JkBmsDataPoints.h

@@ -185,6 +185,10 @@ class DataPoint {
         std::string const& getUnitText() const { return _strUnit; }
         uint32_t getTimestamp() const { return _timestamp; }
 
+        bool operator==(DataPoint const& other) const {
+            return _value == other._value;
+        }
+
     private:
         std::string _strLabel;
         std::string _strValue;

src/BatteryStats.cpp

@@ -1,5 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
+#include <vector>
+#include <algorithm>
 #include "BatteryStats.h"
+#include "Configuration.h"
 #include "MqttSettings.h"
 #include "JkBmsDataPoints.h"
 
@@ -145,6 +148,34 @@ void PylontechBatteryStats::mqttPublish() const
 void JkBmsBatteryStats::mqttPublish() const
 {
     BatteryStats::mqttPublish();
+
+    using Label = JkBms::DataPointLabel;
+
+    static std::vector<Label> mqttSkip = {
+        Label::CellsMilliVolt, // complex data format
+        Label::ModificationPassword, // sensitive data
+        Label::BatterySoCPercent // already published by base class
+    };
+
+    CONFIG_T& config = Configuration.get();
+
+    // publish all topics every minute, unless the retain flag is enabled
+    bool fullPublish = _lastFullMqttPublish + 60 * 1000 < millis();
+    fullPublish &= !config.Mqtt_Retain;
+
+    for (auto iter = _dataPoints.cbegin(); iter != _dataPoints.cend(); ++iter) {
+        // skip data points that did not change since last published
+        if (!fullPublish && iter->second.getTimestamp() < _lastMqttPublish) { continue; }
+
+        auto skipMatch = std::find(mqttSkip.begin(), mqttSkip.end(), iter->first);
+        if (skipMatch != mqttSkip.end()) { continue; }
+
+        String topic((std::string("battery/") + iter->second.getLabelText()).c_str());
+        MqttSettings.publish(topic, iter->second.getValueText().c_str());
+    }
+
+    _lastMqttPublish = millis();
+    if (fullPublish) { _lastFullMqttPublish = _lastMqttPublish; }
 }
 
 void JkBmsBatteryStats::updateFrom(JkBms::DataPointContainer const& dp)

src/JkBmsController.cpp

@@ -312,9 +312,9 @@ void Controller::frameComplete()
             ts, _buffer.size());
         for (size_t ctr = 0; ctr < _buffer.size(); ++ctr) {
             if (ctr % 16 == 0) {
-                MessageOutput.printf("\r\n[%11.3f] JK BMS: ", ts);
+                MessageOutput.printf("\r\n[%11.3f] JK BMS:", ts);
             }
-            MessageOutput.printf("%02x ", _buffer[ctr]);
+            MessageOutput.printf(" %02x", _buffer[ctr]);
         }
         MessageOutput.println();
     }

src/JkBmsDataPoints.cpp

@@ -48,7 +48,14 @@ std::string dataPointValueToStr(tCells const& v) {
 void DataPointContainer::updateFrom(DataPointContainer const& source)
 {
     for (auto iter = source.cbegin(); iter != source.cend(); ++iter) {
-        _dataPoints.erase(iter->first);
+        auto pos = _dataPoints.find(iter->first);
+
+        if (pos != _dataPoints.end()) {
+            // do not update existing data points with the same value
+            if (pos->second == iter->second) { continue; }
+
+            _dataPoints.erase(pos);
+        }
         _dataPoints.insert(*iter);
     }
 }