Feature: support JSON payload in MQTT power meter

the MQTT power meter can now process the messages published at the
respective topics as JSON and extract a power value using a JSON path
(same as in HTTP+JSON power meter). additionally, selecting a unit for
the power value as well as an option to invert the value's sign was
added as well, similar to the HTTPS+JSON power meter.

include/Configuration.h

@@ -79,6 +79,12 @@ using HttpRequestConfig = struct HTTP_REQUEST_CONFIG_T;
 
 struct POWERMETER_MQTT_VALUE_T {
     char Topic[MQTT_MAX_TOPIC_STRLEN + 1];
+    char JsonPath[POWERMETER_HTTP_JSON_MAX_PATH_STRLEN + 1];
+
+    enum Unit { Watts = 0, MilliWatts = 1, KiloWatts = 2 };
+    Unit PowerUnit;
+
+    bool SignInverted;
 };
 using PowerMeterMqttValue = struct POWERMETER_MQTT_VALUE_T;
 

include/PowerMeterMqtt.h

@@ -6,6 +6,7 @@
 #include <espMqttClient.h>
 #include <vector>
 #include <mutex>
+#include <array>
 
 class PowerMeterMqtt : public PowerMeterProvider {
 public:
@@ -23,13 +24,12 @@ private:
     using MsgProperties = espMqttClientTypes::MessageProperties;
     void onMessage(MsgProperties const& properties, char const* topic,
             uint8_t const* payload, size_t len, size_t index,
-            size_t total, float* targetVariable);
+            size_t total, float* targetVariable, PowerMeterMqttValue const* cfg);
 
     PowerMeterMqttConfig const _cfg;
 
-    float _powerValueOne = 0;
+    using power_values_t = std::array<float, POWERMETER_MQTT_MAX_VALUES>;
-    float _powerValueTwo = 0;
+    power_values_t _powerValues;
-    float _powerValueThree = 0;
 
     std::vector<String> _mqttSubscriptions;
 

src/Configuration.cpp

@@ -36,6 +36,9 @@ void ConfigurationClass::serializePowerMeterMqttConfig(PowerMeterMqttConfig cons
         PowerMeterMqttValue const& s = source.Values[i];
 
         t["topic"] = s.Topic;
+        t["json_path"] = s.JsonPath;
+        t["unit"] = s.PowerUnit;
+        t["sign_inverted"] = s.SignInverted;
     }
 }
 
@@ -301,10 +304,14 @@ void ConfigurationClass::deserializeHttpRequestConfig(JsonObject const& source,
 
 void ConfigurationClass::deserializePowerMeterMqttConfig(JsonObject const& source, PowerMeterMqttConfig& target)
 {
-    JsonArray s = source["values"].as<JsonArray>();
     for (size_t i = 0; i < POWERMETER_MQTT_MAX_VALUES; ++i) {
         PowerMeterMqttValue& t = target.Values[i];
-        strlcpy(t.Topic, s[i]["topic"] | "", sizeof(t.Topic));
+        JsonObject s = source["values"][i];
+
+        strlcpy(t.Topic, s["topic"] | "", sizeof(t.Topic));
+        strlcpy(t.JsonPath, s["json_path"] | "", sizeof(t.JsonPath));
+        t.PowerUnit = s["unit"] | PowerMeterMqttValue::Unit::Watts;
+        t.SignInverted = s["sign_inverted"] | false;
     }
 }
 

src/PowerMeterMqtt.cpp

@@ -2,24 +2,27 @@
 #include "PowerMeterMqtt.h"
 #include "MqttSettings.h"
 #include "MessageOutput.h"
+#include "ArduinoJson.h"
+#include "Utils.h"
 
 bool PowerMeterMqtt::init()
 {
-    auto subscribe = [this](char const* topic, float* targetVariable) {
+    auto subscribe = [this](PowerMeterMqttValue const& val, float* targetVariable) {
+        char const* topic = val.Topic;
         if (strlen(topic) == 0) { return; }
         MqttSettings.subscribe(topic, 0,
                 std::bind(&PowerMeterMqtt::onMessage,
                     this, std::placeholders::_1, std::placeholders::_2,
                     std::placeholders::_3, std::placeholders::_4,
                     std::placeholders::_5, std::placeholders::_6,
-                    targetVariable)
+                    targetVariable, &val)
                 );
         _mqttSubscriptions.push_back(topic);
     };
 
-    subscribe(_cfg.Values[0].Topic, &_powerValueOne);
+    for (size_t i = 0; i < _powerValues.size(); ++i) {
-    subscribe(_cfg.Values[1].Topic, &_powerValueTwo);
+        subscribe(_cfg.Values[i], &_powerValues[i]);
-    subscribe(_cfg.Values[2].Topic, &_powerValueThree);
+    }
 
     return _mqttSubscriptions.size() > 0;
 }
@@ -32,22 +35,63 @@ PowerMeterMqtt::~PowerMeterMqtt()
 
 void PowerMeterMqtt::onMessage(PowerMeterMqtt::MsgProperties const& properties,
         char const* topic, uint8_t const* payload, size_t len, size_t index,
-        size_t total, float* targetVariable)
+        size_t total, float* targetVariable, PowerMeterMqttValue const* cfg)
 {
     std::string value(reinterpret_cast<char const*>(payload), len);
+    std::string logValue = value.substr(0, 32);
+    if (value.length() > logValue.length()) { logValue += "..."; }
+
+    auto log= [topic](char const* format, auto&&... args) -> void {
+        MessageOutput.printf("[PowerMeterMqtt] Topic '%s': ", topic);
+        MessageOutput.printf(format, args...);
+        MessageOutput.println();
+    };
+
+    if (strlen(cfg->JsonPath) == 0) {
         try {
             std::lock_guard<std::mutex> l(_mutex);
             *targetVariable = std::stof(value);
         }
         catch (std::invalid_argument const& e) {
-        MessageOutput.printf("[PowerMeterMqtt] cannot parse payload of topic "
+            return log("cannot parse payload '%s' as float", logValue.c_str());
-                "'%s' as float: %s\r\n", topic, value.c_str());
+        }
-        return;
+    }
+    else {
+        JsonDocument json;
+
+        const DeserializationError error = deserializeJson(json, value);
+        if (error) {
+            return log("cannot parse payload '%s' as JSON", logValue.c_str());
         }
 
+        if (json.overflowed()) {
+            return log("payload too large to process as JSON");
+        }
+
+        auto pathResolutionResult = Utils::getJsonValueByPath<float>(json, cfg->JsonPath);
+        if (!pathResolutionResult.second.isEmpty()) {
+            return log("%s", pathResolutionResult.second.c_str());
+        }
+
+        *targetVariable = pathResolutionResult.first;
+    }
+
+    using Unit_t = PowerMeterMqttValue::Unit;
+    switch (cfg->PowerUnit) {
+        case Unit_t::MilliWatts:
+            *targetVariable /= 1000;
+            break;
+        case Unit_t::KiloWatts:
+            *targetVariable *= 1000;
+            break;
+        default:
+            break;
+    }
+
+    if (cfg->SignInverted) { *targetVariable *= -1; }
+
     if (_verboseLogging) {
-        MessageOutput.printf("[PowerMeterMqtt] Updated from '%s', TotalPower: %5.2f\r\n",
+        log("new value: %5.2f, total: %5.2f", *targetVariable, getPowerTotal());
-                topic, getPowerTotal());
     }
 
     gotUpdate();
@@ -55,14 +99,16 @@ void PowerMeterMqtt::onMessage(PowerMeterMqtt::MsgProperties const& properties,
 
 float PowerMeterMqtt::getPowerTotal() const
 {
-    std::lock_guard<std::mutex> l(_mutex);
+    float sum = 0.0;
-    return _powerValueOne + _powerValueTwo + _powerValueThree;
+    std::unique_lock<std::mutex> lock(_mutex);
+    for (auto v: _powerValues) { sum += v; }
+    return sum;
 }
 
 void PowerMeterMqtt::doMqttPublish() const
 {
     std::lock_guard<std::mutex> l(_mutex);
-    mqttPublish("power1", _powerValueOne);
+    mqttPublish("power1", _powerValues[0]);
-    mqttPublish("power2", _powerValueTwo);
+    mqttPublish("power2", _powerValues[1]);
-    mqttPublish("power3", _powerValueThree);
+    mqttPublish("power3", _powerValues[2]);
 }

webapp/src/locales/de.json

@@ -566,6 +566,7 @@
         "typeHTTP_SML": "HTTP(S) + SML (z.B. Tibber Pulse via Tibber Bridge)",
         "MqttValue": "Konfiguration Wert {valueNumber}",
         "MqttTopic": "MQTT Topic",
+        "mqttJsonPath": "Optional: JSON-Pfad",
         "SDM": "SDM-Stromzähler Konfiguration",
         "sdmaddress": "Modbus Adresse",
         "HTTP_JSON": "HTTP(S) + JSON - Allgemeine Konfiguration",
@@ -575,11 +576,11 @@
         "jsonPathExamplesExplanation": "Die folgenden Pfade finden jeweils den Wert '123.4' im jeweiligen Beispiel-JSON.",
         "httpValue": "Konfiguration Wert {valueNumber}",
         "httpEnabled": "Wert aktiviert",
-        "httpJsonPath": "JSON-Pfad",
+        "valueJsonPath": "JSON-Pfad",
-        "httpJsonPathDescription": "Anwendungsspezifischer JSON-Pfad um den Leistungswert in the HTTP(S) Antwort zu finden, z.B. 'power/total/watts' oder nur 'total'.",
+        "valueJsonPathDescription": "Anwendungsspezifischer JSON-Pfad um den Leistungswert in den JSON Nutzdatzen zu finden, z.B. 'power/total/watts' oder nur 'total'.",
-        "httpUnit": "Einheit",
+        "valueUnit": "Einheit",
-        "httpSignInverted": "Vorzeichen umkehren",
+        "valueSignInverted": "Vorzeichen umkehren",
-        "httpSignInvertedHint": "Positive Werte werden als Leistungsabnahme aus dem Netz interpretiert. Diese Option muss aktiviert werden, wenn das Vorzeichen des Wertes die gegenteilige Bedeutung hat.",
+        "valueSignInvertedHint": "Positive Werte werden als Leistungsabnahme aus dem Netz interpretiert. Diese Option muss aktiviert werden, wenn das Vorzeichen des Wertes die gegenteilige Bedeutung hat.",
         "testHttpJsonHeader": "Konfiguration testen",
         "testHttpJsonRequest": "HTTP(S)-Anfrage(n) senden und Antwort(en) verarbeiten",
         "testHttpSmlHeader": "Konfiguration testen",

webapp/src/locales/en.json

@@ -567,6 +567,7 @@
         "typeSMAHM2": "SMA Homemanager 2.0",
         "typeHTTP_SML": "HTTP(S) + SML (e.g. Tibber Pulse via Tibber Bridge)",
         "MqttValue": "Value {valueNumber} Configuration",
+        "mqttJsonPath": "Optional: JSON Path",
         "MqttTopic": "MQTT Topic",
         "SDM": "SDM-Power Meter Parameter",
         "sdmaddress": "Modbus Address",
@@ -577,11 +578,11 @@
         "jsonPathExamplesExplanation": "The following paths each find the value '123.4' in the respective example JSON.",
         "httpValue": "Value {valueNumber} Configuration",
         "httpEnabled": "Value Enabled",
-        "httpJsonPath": "JSON Path",
+        "valueJsonPath": "JSON Path",
-        "httpJsonPathDescription": "Application specific JSON path to find the power value in the HTTP(S) response, e.g., 'power/total/watts' or simply 'total'.",
+        "valueJsonPathDescription": "Application specific JSON path to find the power value in the JSON payload, e.g., 'power/total/watts' or simply 'total'.",
-        "httpUnit": "Unit",
+        "valueUnit": "Unit",
-        "httpSignInverted": "Change Sign",
+        "valueSignInverted": "Change Sign",
-        "httpSignInvertedHint": "Is is expected that positive values denote power usage from the grid. Check this option if the sign of this value has the opposite meaning.",
+        "valueSignInvertedHint": "Is is expected that positive values denote power usage from the grid. Check this option if the sign of this value has the opposite meaning.",
         "testHttpJsonHeader": "Test Configuration",
         "testHttpJsonRequest": "Send HTTP(S) request(s) and process response(s)",
         "testHttpSmlHeader": "Test Configuration",

webapp/src/types/PowerMeterConfig.ts

@@ -2,6 +2,9 @@ import type { HttpRequestConfig } from '@/types/HttpRequestConfig';
 
 export interface PowerMeterMqttValue {
     topic: string;
+    json_path: string;
+    unit: number;
+    sign_inverted: boolean;
 }
 
 export interface PowerMeterMqttConfig {

webapp/src/views/PowerMeterAdminView.vue

@@ -30,6 +30,18 @@
             </CardElement>
 
             <div v-if="powerMeterConfigList.enabled">
+                <div v-if="powerMeterConfigList.source === 0 || powerMeterConfigList.source === 3">
+                    <div class="alert alert-secondary mt-5" role="alert">
+                        <h2>{{ $t('powermeteradmin.jsonPathExamplesHeading') }}:</h2>
+                        {{ $t('powermeteradmin.jsonPathExamplesExplanation') }}
+                        <ul>
+                            <li><code>power/total/watts</code> &mdash; <code>{ "power": { "phase1": { "factor": 0.98, "watts": 42 }, "total": { "watts": 123.4 } } }</code></li>
+                            <li><code>data/[1]/power</code> &mdash; <code>{ "data": [ { "factor": 0.98, "power": 42 }, { "factor": 1.0, "power": 123.4 } ] } }</code></li>
+                            <li><code>total</code> &mdash; <code>{ "othervalue": 66, "total": 123.4 }</code></li>
+                        </ul>
+                    </div>
+                </div>
+
                 <CardElement v-if="powerMeterConfigList.source === 0"
                         v-for="(mqtt, index) in powerMeterConfigList.mqtt.values"
                         :text="$t('powermeteradmin.MqttValue', { valueNumber: index + 1})"
@@ -41,6 +53,33 @@
                         type="text"
                         maxlength="256"
                         wide />
+
+                    <InputElement :label="$t('powermeteradmin.mqttJsonPath')"
+                        v-model="mqtt.json_path"
+                        type="text"
+                        maxlength="256"
+                        :tooltip="$t('powermeteradmin.valueJsonPathDescription')"
+                        wide />
+
+                    <div class="row mb-3">
+                        <label for="mqtt_power_unit" class="col-sm-4 col-form-label">
+                            {{ $t('powermeteradmin.valueUnit') }}
+                        </label>
+                        <div class="col-sm-8">
+                            <select id="mqtt_power_unit" class="form-select" v-model="mqtt.unit">
+                                <option v-for="u in unitTypeList" :key="u.key" :value="u.key">
+                                    {{ u.value }}
+                                </option>
+                            </select>
+                        </div>
+                    </div>
+
+                    <InputElement
+                        :label="$t('powermeteradmin.valueSignInverted')"
+                        v-model="mqtt.sign_inverted"
+                        :tooltip="$t('powermeteradmin.valueSignInvertedHint')"
+                        type="checkbox"
+                        wide />
                 </CardElement>
 
                 <CardElement v-if="(powerMeterConfigList.source === 1 || powerMeterConfigList.source === 2)"
@@ -63,6 +102,16 @@
                 </CardElement>
 
                 <div v-if="powerMeterConfigList.source === 3">
+                    <div class="alert alert-secondary mt-5" role="alert">
+                        <h2>{{ $t('powermeteradmin.urlExamplesHeading') }}:</h2>
+                        <ul>
+                            <li>http://shelly3em.home/status</li>
+                            <li>https://shelly3em.home/status</li>
+                            <li>http://tasmota-123.home/cm?cmnd=status%208</li>
+                            <li>http://12.34.56.78:8080/emeter/0</li>
+                        </ul>
+                    </div>
+
                     <CardElement :text="$t('powermeteradmin.HTTP')"
                             textVariant="text-bg-primary"
                             add-space>
@@ -80,24 +129,6 @@
                             wide />
                     </CardElement>
 
-                    <div class="alert alert-secondary mt-5" role="alert">
-                        <h2>{{ $t('powermeteradmin.urlExamplesHeading') }}:</h2>
-                        <ul>
-                            <li>http://shelly3em.home/status</li>
-                            <li>https://shelly3em.home/status</li>
-                            <li>http://tasmota-123.home/cm?cmnd=status%208</li>
-                            <li>http://12.34.56.78:8080/emeter/0</li>
-                        </ul>
-
-                        <h2>{{ $t('powermeteradmin.jsonPathExamplesHeading') }}:</h2>
-                        {{ $t('powermeteradmin.jsonPathExamplesExplanation') }}
-                        <ul>
-                            <li><code>power/total/watts</code> &mdash; <code>{ "power": { "phase1": { "factor": 0.98, "watts": 42 }, "total": { "watts": 123.4 } } }</code></li>
-                            <li><code>data/[1]/power</code> &mdash; <code>{ "data": [ { "factor": 0.98, "power": 42 }, { "factor": 1.0, "power": 123.4 } ] } }</code></li>
-                            <li><code>total</code> &mdash; <code>{ "othervalue": 66, "total": 123.4 }</code></li>
-                        </ul>
-                    </div>
-
                     <CardElement
                             v-for="(httpJson, index) in powerMeterConfigList.http_json.values"
                             :key="index"
@@ -114,17 +145,17 @@
 
                             <HttpRequestSettings :cfg="httpJson.http_request" v-if="index == 0 || powerMeterConfigList.http_json.individual_requests"/>
 
-                            <InputElement :label="$t('powermeteradmin.httpJsonPath')"
+                            <InputElement :label="$t('powermeteradmin.valueJsonPath')"
                                 v-model="httpJson.json_path"
                                 type="text"
                                 maxlength="256"
                                 placeholder="total_power"
-                                :tooltip="$t('powermeteradmin.httpJsonPathDescription')"
+                                :tooltip="$t('powermeteradmin.valueJsonPathDescription')"
                                 wide />
 
                             <div class="row mb-3">
                                 <label for="power_unit" class="col-sm-4 col-form-label">
-                                    {{ $t('powermeteradmin.httpUnit') }}
+                                    {{ $t('powermeteradmin.valueUnit') }}
                                 </label>
                                 <div class="col-sm-8">
                                     <select id="power_unit" class="form-select" v-model="httpJson.unit">
@@ -136,9 +167,9 @@
                             </div>
 
                             <InputElement
-                                :label="$t('powermeteradmin.httpSignInverted')"
+                                :label="$t('powermeteradmin.valueSignInverted')"
                                 v-model="httpJson.sign_inverted"
-                                :tooltip="$t('powermeteradmin.httpSignInvertedHint')"
+                                :tooltip="$t('powermeteradmin.valueSignInvertedHint')"
                                 type="checkbox"
                                 wide />
                         </div>