sunspec: add Fronius vendor with its own control rules

Adds a fronius vendor and a froniusConnection thing class alongside the
generic sunspec and solarEdge ones, following the SolarEdge mechanism but
none of its workarounds - no proprietary battery block and no PV
production computed by difference, since the GEN24 exposes model 160.

FroniusRules holds the vendor decisions as pure functions:

  - discovery only keeps devices announcing Fronius as manufacturer;
  - the byte order is the SunSpec default, not the forced big endian that
    is specific to SolarEdge, and no endianness parameter is exposed;
  - meterSlaveId defaults to 200, 0 meaning no meter on this connection;
  - a hard 7 s floor on the poll interval. Polling faster can push the
    inverter offline towards the vendor portal, and recovery needs an
    AC+DC power cycle on site, so this is a guard in the code rather than
    a configurable default;
  - the registers the inverter accepts and then silently ignores are
    refused before anything reaches the wire;
  - the six HEMS battery modes map onto ChaGriSet, StorCtl_Mod, InWRte and
    OutWRte, negative meaning charge;
  - model 160 blocks are classified by IDStr, never by index: on a three
    or four MPPT inverter the battery blocks are not in position 3 and 4.

Storages under a Fronius connection default revertTime to 300 s.

Setpoints now reread the scale factor before writing and read the written
registers back afterwards, reporting a mismatch through a new
controlHealthy state - the only defence against writes that are accepted
and then ignored without a Modbus exception.

Byte order and the revert timer semantics on model 124 are inferences, not
measurements; see specs/fronius-sunspec.md, H-2 and H-3.

sunspec/froniusrules.cpp

@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+*
+* Copyright (C) 2026, ETM-PowerSync
+*
+* This file is part of nymea.
+*
+* nymea is free software: you can redistribute it and/or modify it under the
+* terms of the GNU General Public License as published by the Free Software
+* Foundation, either version 3 of the License, or (at your option) any later
+* version.
+*
+* nymea is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License along with
+* nymea. If not, see <https://www.gnu.org/licenses/>.
+*
+* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+#include "froniusrules.h"
+
+using namespace SunSpecStorageLogic;
+
+namespace FroniusRules {
+
+bool matchesManufacturer(const QStringList &manufacturers)
+{
+    foreach (const QString &name, manufacturers) {
+        if (name.contains(QStringLiteral("fronius"), Qt::CaseInsensitive))
+            return true;
+    }
+    return false;
+}
+
+SunSpecDataPoint::ByteOrder byteOrder()
+{
+    return SunSpecDataPoint::ByteOrderLittleEndian;
+}
+
+int clampUpdateInterval(int requestedSeconds)
+{
+    return qMax(requestedSeconds, MinimumUpdateIntervalSeconds);
+}
+
+bool isWriteForbidden(const QString &registerName)
+{
+    static const QStringList forbidden = {
+        QStringLiteral("WChaMax"),
+        QStringLiteral("WChaGra"),
+        QStringLiteral("WDisChaGra"),
+        QStringLiteral("InOutWRte_WinTms"),
+        QStringLiteral("InOutWRte_RmpTms"),
+        /* VAChaMax is doubly unusable: the write is ignored and its scale
+         * factor is not supported either. */
+        QStringLiteral("VAChaMax")
+    };
+
+    foreach (const QString &name, forbidden) {
+        if (registerName.compare(name, Qt::CaseInsensitive) == 0)
+            return true;
+    }
+    return false;
+}
+
+SetpointPlan planBatteryMode(BatteryMode mode, double chargeLimit, double dischargeLimit, quint16 revertTime)
+{
+    /* StorCtl_Mod is a bitfield: bit 0 CHARGE, bit 1 DISCHARGE. ChaGriSet is
+     * 0 PV, 1 GRID. A register absent from the vector below is deliberately not
+     * written for that mode.
+     *
+     * planSetpoint() puts these in the mandated order and appends the revert
+     * timer, so the order they are listed in here does not matter. */
+    QVector<Write> setpoints;
+
+    switch (mode) {
+    case BatteryModeNormal:
+        setpoints.append({RegisterStorCtlMod, 0});
+        setpoints.append({RegisterOutWRte, 100});
+        break;
+
+    case BatteryModeNoDischarge:
+        setpoints.append({RegisterStorCtlMod, 2});
+        setpoints.append({RegisterOutWRte, 0});
+        break;
+
+    case BatteryModeNoCharge:
+        setpoints.append({RegisterStorCtlMod, 1});
+        setpoints.append({RegisterInWRte, 0});
+        break;
+
+    case BatteryModeFrozen:
+        setpoints.append({RegisterStorCtlMod, 3});
+        setpoints.append({RegisterInWRte, 0});
+        setpoints.append({RegisterOutWRte, 0});
+        break;
+
+    case BatteryModeForceCharge:
+        /* Charging from the grid has to be allowed on the inverter as well;
+         * ChaGriSet alone is ANDed with a setting of the component
+         * configuration and fails silently if that one is off. */
+        setpoints.append({RegisterChaGriSet, 1});
+        setpoints.append({RegisterStorCtlMod, 2});
+        /* Negative is charging. */
+        setpoints.append({RegisterOutWRte, -chargeLimit});
+        break;
+
+    case BatteryModeLimit:
+        setpoints.append({RegisterStorCtlMod, 3});
+        setpoints.append({RegisterInWRte, chargeLimit});
+        setpoints.append({RegisterOutWRte, dischargeLimit});
+        break;
+    }
+
+    return planSetpoint(setpoints, revertTime);
+}
+
+BlockRole classifyBlock(const QString &inputIdString)
+{
+    const QString id = inputIdString.trimmed();
+    if (id.isEmpty())
+        return BlockRoleUnknown;
+
+    /* Prefix match, not contains: the role is decided by the string, never by
+     * the block index. StDisCha is checked first so that no cascade can ever
+     * swallow it into the charge case. */
+    if (id.startsWith(QStringLiteral("StDisCha"), Qt::CaseInsensitive))
+        return BlockRoleBatteryDischarge;
+
+    if (id.startsWith(QStringLiteral("StCha"), Qt::CaseInsensitive))
+        return BlockRoleBatteryCharge;
+
+    if (id.startsWith(QStringLiteral("MPPT"), Qt::CaseInsensitive))
+        return BlockRolePvString;
+
+    return BlockRoleUnknown;
+}
+
+double pvPower(const QList<ModuleReading> &readings)
+{
+    double total = 0;
+    foreach (const ModuleReading &reading, readings) {
+        if (classifyBlock(reading.inputIdString) == BlockRolePvString)
+            total += reading.dcPower;
+    }
+    return total;
+}
+
+double batteryPower(const QList<ModuleReading> &readings)
+{
+    double charging = 0;
+    double discharging = 0;
+
+    foreach (const ModuleReading &reading, readings) {
+        switch (classifyBlock(reading.inputIdString)) {
+        case BlockRoleBatteryCharge:
+            charging += reading.dcPower;
+            break;
+        case BlockRoleBatteryDischarge:
+            discharging += reading.dcPower;
+            break;
+        default:
+            break;
+        }
+    }
+
+    return discharging - charging;
+}
+
+}

sunspec/froniusrules.h

@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+*
+* Copyright (C) 2026, ETM-PowerSync
+*
+* This file is part of nymea.
+*
+* nymea is free software: you can redistribute it and/or modify it under the
+* terms of the GNU General Public License as published by the Free Software
+* Foundation, either version 3 of the License, or (at your option) any later
+* version.
+*
+* nymea is distributed in the hope that it will be useful, but WITHOUT ANY
+* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License along with
+* nymea. If not, see <https://www.gnu.org/licenses/>.
+*
+* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+#ifndef FRONIUSRULES_H
+#define FRONIUSRULES_H
+
+#include <QList>
+#include <QString>
+#include <QStringList>
+
+#include <sunspecdatapoint.h>
+
+#include "sunspecstoragelogic.h"
+
+/* Vendor specific rules for Fronius GEN24 inverters.
+ *
+ * Everything here is a pure decision: no Modbus, no thing, no timer. The
+ * plugin asks these functions what to do; the answers are what the unit tests
+ * pin down. See specs/fronius-sunspec.md.
+ */
+namespace FroniusRules {
+
+/* Polling. The manufacturer's support recommends staying above seven seconds
+ * for third party applications. Below that, communication load can push the
+ * inverter offline towards the manufacturer's portal, and recovery needs an
+ * AC+DC power cycle on site. This floor is a guard in the code, not a
+ * configurable default. */
+const int MinimumUpdateIntervalSeconds = 7;
+const int DefaultUpdateIntervalSeconds = 10;
+const int DefaultTimeoutMilliSeconds = 2000;
+const int DefaultNumberOfRetries = 3;
+
+/* Revert timer armed with every setpoint, so that a setpoint left behind by a
+ * stopped or crashed HEMS expires instead of holding the battery forever.
+ *
+ * WORKING HYPOTHESIS: the timer semantics are documented in the manual's
+ * general chapter and illustrated on model 123, not on model 124. This must be
+ * verified experimentally on model 124 before being frozen. If it does not
+ * hold, fall back to 0 plus an application level watchdog in the HEMS. */
+const int DefaultRevertTimeSeconds = 300;
+
+/* Default unit IDs. The inverter is fixed at 1 over TCP; the meter defaults to
+ * 200, with 201, 202... for secondary meters. 0 means "no meter on this
+ * connection". */
+const int InverterSlaveId = 1;
+const int DefaultMeterSlaveId = 200;
+
+bool matchesManufacturer(const QStringList &manufacturers);
+
+/* INFERRED: the byte order of the GEN24 is not documented by the manufacturer,
+ * so the SunSpec default is assumed. The forced big endian of the SolarEdge
+ * vendor is an anomaly specific to SolarEdge and must not be extended here.
+ * To be confirmed on the bench, then on hardware. */
+SunSpecDataPoint::ByteOrder byteOrder();
+
+int clampUpdateInterval(int requestedSeconds);
+
+/* Registers the GEN24 accepts and then ignores without raising a Modbus
+ * exception. Writing them fails invisibly, so they are refused before being
+ * put on the wire. */
+bool isWriteForbidden(const QString &registerName);
+
+enum BatteryMode {
+    BatteryModeNormal,
+    BatteryModeNoDischarge,
+    BatteryModeNoCharge,
+    BatteryModeFrozen,
+    BatteryModeForceCharge,
+    BatteryModeLimit
+};
+
+/* Sign convention of the manufacturer: negative is charging, positive is
+ * discharging. chargeLimit and dischargeLimit are percentages of WChaMax and
+ * are only used by the modes that need them. */
+SunSpecStorageLogic::SetpointPlan planBatteryMode(BatteryMode mode,
+                                                  double chargeLimit,
+                                                  double dischargeLimit,
+                                                  quint16 revertTime);
+
+/* Model 160 repeating blocks are identified by their IDStr, never by their
+ * index: on a three or four MPPT inverter the battery blocks are not in
+ * position 3 and 4. */
+enum BlockRole {
+    BlockRolePvString,
+    BlockRoleBatteryCharge,
+    BlockRoleBatteryDischarge,
+    BlockRoleUnknown
+};
+
+BlockRole classifyBlock(const QString &inputIdString);
+
+struct ModuleReading {
+    QString inputIdString;
+    double dcPower;
+};
+
+/* Sum of the DC power of the PV string blocks. */
+double pvPower(const QList<ModuleReading> &readings);
+
+/* Discharge minus charge, so positive means discharging. DCW is a uint16 and
+ * therefore always positive: the sign is carried by whichever block is active,
+ * the inactive one reading zero. */
+double batteryPower(const QList<ModuleReading> &readings);
+
+}
+
+#endif // FRONIUSRULES_H

sunspec/integrationpluginsunspec.cpp

@@ -66,21 +66,27 @@ void IntegrationPluginSunSpec::init()
     // SunSpec connection params
     m_connectionDiscoverySlaveIdParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionDiscoverySlaveIdParamTypeId);
     m_connectionDiscoverySlaveIdParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionDiscoverySlaveIdParamTypeId);
+    m_connectionDiscoverySlaveIdParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionDiscoverySlaveIdParamTypeId);
 
     m_connectionMacAddressParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionThingMacAddressParamTypeId);
     m_connectionMacAddressParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionThingMacAddressParamTypeId);
+    m_connectionMacAddressParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionThingMacAddressParamTypeId);
 
     m_connectionHostNameParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionThingHostNameParamTypeId);
     m_connectionHostNameParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionThingHostNameParamTypeId);
+    m_connectionHostNameParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionThingHostNameParamTypeId);
 
     m_connectionAddressParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionThingAddressParamTypeId);
     m_connectionAddressParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionThingAddressParamTypeId);
+    m_connectionAddressParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionThingAddressParamTypeId);
 
     m_connectionPortParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionThingPortParamTypeId);
     m_connectionPortParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionThingPortParamTypeId);
+    m_connectionPortParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionThingPortParamTypeId);
 
     m_connectionSlaveIdParamTypeIds.insert(sunspecConnectionThingClassId, sunspecConnectionThingSlaveIdParamTypeId);
     m_connectionSlaveIdParamTypeIds.insert(solarEdgeConnectionThingClassId, solarEdgeConnectionThingSlaveIdParamTypeId);
+    m_connectionSlaveIdParamTypeIds.insert(froniusConnectionThingClassId, froniusConnectionThingSlaveIdParamTypeId);
 
     // Params for sunspec things
     m_modelIdParamTypeIds.insert(sunspecSinglePhaseInverterThingClassId, sunspecSinglePhaseInverterThingModelIdParamTypeId);
@@ -140,6 +146,8 @@ void IntegrationPluginSunSpec::discoverThings(ThingDiscoveryInfo *info)
     SunSpecDataPoint::ByteOrder byteOrder = SunSpecDataPoint::ByteOrderLittleEndian;
     if (info->thingClassId() == solarEdgeConnectionThingClassId)
         byteOrder = SunSpecDataPoint::ByteOrderBigEndian;
+    else if (info->thingClassId() == froniusConnectionThingClassId)
+        byteOrder = FroniusRules::byteOrder();
 
     quint16 discoverySlaveId = info->params().paramValue(m_connectionDiscoverySlaveIdParamTypeIds.value(info->thingClassId())).toUInt();
 
@@ -165,6 +173,12 @@ void IntegrationPluginSunSpec::discoverThings(ThingDiscoveryInfo *info)
                 } else {
                     manufacturer = "SolarEdge";
                 }
+            } else if (info->thingClassId() == froniusConnectionThingClassId) {
+                if (!FroniusRules::matchesManufacturer(result.modelManufacturers)) {
+                    // Only offer devices that actually announce themselves as Fronius.
+                    continue;
+                }
+                manufacturer = "Fronius";
             } else if (info->thingClassId() == sunspecConnectionThingClassId) {
                 // There are some issues regarding the sunspec implementation of kostal.
                 // Full support of meter, inverter and storage will be provided in the kostal plugin which makes
@@ -416,7 +430,7 @@ void IntegrationPluginSunSpec::postSetupThing(Thing *thing)
     // Create the refresh timer if not already set up
     if (!m_refreshTimer) {
         qCDebug(dcSunSpec()) << "Starting refresh timer";
-        int refreshTime = configValue(sunSpecPluginUpdateIntervalParamTypeId).toInt();
+        int refreshTime = effectiveUpdateInterval();
         m_refreshTimer = hardwareManager()->pluginTimerManager()->registerTimer(refreshTime);
         connect(m_refreshTimer, &PluginTimer::timeout, this, &IntegrationPluginSunSpec::onRefreshTimer);
     }
@@ -509,6 +523,36 @@ void IntegrationPluginSunSpec::executeAction(ThingActionInfo *info)
     }
 }
 
+/* The refresh timer is plugin wide, not per connection, so the Fronius polling
+ * floor has to be applied to it: as soon as one Fronius connection is
+ * configured, the whole plugin stops polling faster than the floor.
+ *
+ * Going below it can push the inverter offline towards the manufacturer's
+ * portal, and recovery then needs an AC+DC power cycle on site. This is a guard
+ * in the code on purpose, not a configurable default - including in debug. */
+int IntegrationPluginSunSpec::effectiveUpdateInterval()
+{
+    const int configured = configValue(sunSpecPluginUpdateIntervalParamTypeId).toInt();
+
+    if (myThings().filterByThingClassId(froniusConnectionThingClassId).isEmpty())
+        return configured;
+
+    const int clamped = FroniusRules::clampUpdateInterval(configured);
+    if (clamped != configured) {
+        qCWarning(dcSunSpec()) << "Update interval of" << configured << "s is below the"
+                               << FroniusRules::MinimumUpdateIntervalSeconds
+                               << "s floor required while a Fronius connection is configured. Using"
+                               << clamped << "s instead.";
+    }
+    return clamped;
+}
+
+bool IntegrationPluginSunSpec::isFroniusChild(const ThingId &parentId)
+{
+    Thing *parent = myThings().findById(parentId);
+    return parent && parent->thingClassId() == froniusConnectionThingClassId;
+}
+
 QModbusReply *IntegrationPluginSunSpec::writeSetpointRegister(SunSpecStorageModel *storage, const SunSpecStorageLogic::Write &write)
 {
     switch (write.reg) {
@@ -533,12 +577,32 @@ QModbusReply *IntegrationPluginSunSpec::writeSetpointRegister(SunSpecStorageMode
 void IntegrationPluginSunSpec::executeSetpointWrite(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan, int index)
 {
     if (index >= plan.writes.count()) {
-        info->finish(Thing::ThingErrorNoError);
+        if (plan.verifyReadback.isEmpty()) {
+            info->finish(Thing::ThingErrorNoError);
+            return;
+        }
+
+        refreshStorageBlock(info, storage, [this, info, storage, plan]() {
+            verifySetpointPlan(info, storage, plan);
+        });
         return;
     }
 
     const SunSpecStorageLogic::Write write = plan.writes.at(index);
 
+    /* Defence in depth: a Fronius inverter accepts some writes and then ignores
+     * them without raising a Modbus exception, so the failure is invisible.
+     * Those registers are refused before anything goes on the wire rather than
+     * silently pretending to have worked. */
+    if (isFroniusChild(info->thing()->parentId())
+        && FroniusRules::isWriteForbidden(SunSpecStorageLogic::registerName(write.reg))) {
+        qCWarning(dcSunSpec()) << "Refusing to write" << SunSpecStorageLogic::registerName(write.reg)
+                               << "on" << info->thing()
+                               << "- this register is ignored by the inverter without raising an exception.";
+        info->finish(Thing::ThingErrorHardwareFailure);
+        return;
+    }
+
     QModbusReply *reply = writeSetpointRegister(storage, write);
     if (!reply) {
         qCWarning(dcSunSpec()) << "Could not write" << SunSpecStorageLogic::registerName(write.reg) << "on" << info->thing();
@@ -559,9 +623,95 @@ void IntegrationPluginSunSpec::executeSetpointWrite(ThingActionInfo *info, SunSp
     });
 }
 
+double IntegrationPluginSunSpec::readSetpointRegister(SunSpecStorageModel *storage, SunSpecStorageLogic::Register reg)
+{
+    switch (reg) {
+    case SunSpecStorageLogic::RegisterChaGriSet:
+        return storage->chaGriSet();
+    case SunSpecStorageLogic::RegisterStorCtlMod:
+        return int(storage->storCtlMod());
+    case SunSpecStorageLogic::RegisterInWRte:
+        return storage->inWRte();
+    case SunSpecStorageLogic::RegisterOutWRte:
+        return storage->outWRte();
+    case SunSpecStorageLogic::RegisterRvrtTms:
+        return storage->inOutWRteRvrtTms();
+    }
+    return 0;
+}
+
+/* Reads the model block again and calls the continuation once the fresh values
+ * are in. The guard timer keeps a lost or unanswered read from stranding the
+ * action forever; the continuation then runs on stale values, which is why it
+ * warns. */
+void IntegrationPluginSunSpec::refreshStorageBlock(ThingActionInfo *info, SunSpecStorageModel *storage, const std::function<void()> &continuation)
+{
+    QObject *context = new QObject(info);
+    QSharedPointer<bool> fired = QSharedPointer<bool>::create(false);
+
+    auto proceed = [context, fired, continuation](bool timedOut) {
+        if (*fired)
+            return;
+        *fired = true;
+        if (timedOut)
+            qCWarning(dcSunSpec()) << "Timed out waiting for a fresh storage block; continuing on the previous values.";
+        context->deleteLater();
+        continuation();
+    };
+
+    connect(storage, &SunSpecModel::blockUpdated, context, [proceed]() { proceed(false); });
+
+    QTimer *guard = new QTimer(context);
+    guard->setSingleShot(true);
+    guard->setInterval(FroniusRules::DefaultTimeoutMilliSeconds * (FroniusRules::DefaultNumberOfRetries + 1));
+    connect(guard, &QTimer::timeout, context, [proceed]() { proceed(true); });
+    guard->start();
+
+    storage->readBlockData();
+}
+
+/* Write, read back, compare. An inverter may accept a write and then ignore it
+ * without raising a Modbus exception - control not enabled on the device, grid
+ * charging not allowed, an IP restriction, or another controller overwriting
+ * the setpoints. An unverified setpoint is an unapplied setpoint. */
+void IntegrationPluginSunSpec::verifySetpointPlan(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan)
+{
+    bool healthy = true;
+
+    foreach (const SunSpecStorageLogic::Write &write, plan.writes) {
+        if (!plan.verifyReadback.contains(write.reg))
+            continue;
+
+        const double readBack = readSetpointRegister(storage, write.reg);
+
+        /* The rates carry a scale factor of -2, so anything within a hundredth
+         * is the same value. The enums and the bitfield compare exactly. */
+        const double tolerance = SunSpecStorageLogic::isScaledRate(write.reg) ? 0.011 : 0.0001;
+        if (qAbs(readBack - write.value) > tolerance) {
+            qCWarning(dcSunSpec()) << "Setpoint not applied on" << info->thing() << ":"
+                                   << SunSpecStorageLogic::registerName(write.reg)
+                                   << "was written as" << write.value << "but reads back as" << readBack;
+            healthy = false;
+        }
+    }
+
+    info->thing()->setStateValue(sunspecStorageControlHealthyStateTypeId, healthy);
+    info->finish(Thing::ThingErrorNoError);
+}
+
 void IntegrationPluginSunSpec::executeSetpointPlan(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan)
 {
-    executeSetpointWrite(info, storage, plan, 0);
+    if (!plan.rereadScaleFactor) {
+        executeSetpointWrite(info, storage, plan, 0);
+        return;
+    }
+
+    /* Scale factors are not guaranteed static: they may change with firmware
+     * and at runtime. A factor cached during an earlier poll can put the
+     * setpoint an order of magnitude off, so refresh it right before writing. */
+    refreshStorageBlock(info, storage, [this, info, storage, plan]() {
+        executeSetpointWrite(info, storage, plan, 0);
+    });
 }
 
 Thing *IntegrationPluginSunSpec::getThingForSunSpecModel(uint modelId, uint modbusAddress, const ThingId &parentId)
@@ -716,6 +866,9 @@ SunSpecConnection *IntegrationPluginSunSpec::createConnection(Thing *thing)
         // Note: for some reason, solar edge is using big endian register order instead
         // of little endian as specified in sunspec and even solar edge documentation
         connection = new SunSpecConnection(address, port, slaveId, SunSpecDataPoint::ByteOrderBigEndian, this);
+    } else if (thing->thingClassId() == froniusConnectionThingClassId) {
+        // No endianness parameter here: the byte order is imposed, not chosen.
+        connection = new SunSpecConnection(address, port, slaveId, FroniusRules::byteOrder(), this);
     } else {
         SunSpecDataPoint::ByteOrder endianness = SunSpecDataPoint::ByteOrderLittleEndian;
         QString endiannessParam = thing->paramValue("endianness").toString();
@@ -724,8 +877,14 @@ SunSpecConnection *IntegrationPluginSunSpec::createConnection(Thing *thing)
 
         connection = new SunSpecConnection(address, port, slaveId, endianness, this);
     }
-    connection->setTimeout(configValue(sunSpecPluginTimeoutParamTypeId).toUInt());
+
-    connection->setNumberOfRetries(configValue(sunSpecPluginNumberOfRetriesParamTypeId).toUInt());
+    if (thing->thingClassId() == froniusConnectionThingClassId) {
+        connection->setTimeout(FroniusRules::DefaultTimeoutMilliSeconds);
+        connection->setNumberOfRetries(FroniusRules::DefaultNumberOfRetries);
+    } else {
+        connection->setTimeout(configValue(sunSpecPluginTimeoutParamTypeId).toUInt());
+        connection->setNumberOfRetries(configValue(sunSpecPluginNumberOfRetriesParamTypeId).toUInt());
+    }
 
     // Reconnect on monitor reachable changed
     NetworkDeviceMonitor *monitor = m_monitors.value(thing);
@@ -979,6 +1138,15 @@ void IntegrationPluginSunSpec::autocreateSunSpecModelThing(const ThingClassId &t
     params.append(Param(m_manufacturerParamTypeIds.value(descriptor.thingClassId()), model->commonModelInfo().manufacturerName));
     params.append(Param(m_deviceModelParamTypeIds.value(descriptor.thingClassId()), model->commonModelInfo().modelName));
     params.append(Param(m_serialNumberParamTypeIds.value(descriptor.thingClassId()), model->commonModelInfo().serialNumber));
+
+    /* A storage created under a Fronius connection arms the revert timer by
+     * default, where the generic vendor leaves it disabled. A setpoint left
+     * behind by a stopped HEMS would otherwise hold the customer's battery
+     * indefinitely. */
+    if (thingClassId == sunspecStorageThingClassId && isFroniusChild(parentId)) {
+        params.append(Param(sunspecStorageThingRevertTimeParamTypeId, FroniusRules::DefaultRevertTimeSeconds));
+    }
+
     descriptor.setParams(params);
     emit autoThingsAppeared({descriptor});
 }
@@ -1236,7 +1404,7 @@ void IntegrationPluginSunSpec::onPluginConfigurationChanged(const ParamTypeId &p
     if (paramTypeId == sunSpecPluginUpdateIntervalParamTypeId) {
         qCDebug(dcSunSpec()) << "Update interval has changed" << value.toInt();
         if (m_refreshTimer) {
-            int refreshTime = value.toInt();
+            int refreshTime = effectiveUpdateInterval();
             m_refreshTimer->stop();
             hardwareManager()->pluginTimerManager()->unregisterTimer(m_refreshTimer);
             m_refreshTimer = hardwareManager()->pluginTimerManager()->registerTimer(refreshTime);

sunspec/integrationpluginsunspec.h

@@ -34,6 +34,7 @@
 
 #include "sunspecthing.h"
 #include "sunspecstoragelogic.h"
+#include "froniusrules.h"
 #include "extern-plugininfo.h"
 
 #include <QUuid>
@@ -109,10 +110,17 @@ private:
     bool hasManufacturer(const QStringList &manufacturers, const QString &manufacturer);
     void markThingStatesDisconnected(Thing *thing);
 
+    // Fronius
+    bool isFroniusChild(const ThingId &parentId);
+    int effectiveUpdateInterval();
+
     // Storage setpoints
     void executeSetpointPlan(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan);
     void executeSetpointWrite(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan, int index);
     QModbusReply *writeSetpointRegister(SunSpecStorageModel *storage, const SunSpecStorageLogic::Write &write);
+    double readSetpointRegister(SunSpecStorageModel *storage, SunSpecStorageLogic::Register reg);
+    void refreshStorageBlock(ThingActionInfo *info, SunSpecStorageModel *storage, const std::function<void()> &continuation);
+    void verifySetpointPlan(ThingActionInfo *info, SunSpecStorageModel *storage, const SunSpecStorageLogic::SetpointPlan &plan);
 
 private slots:
     void onRefreshTimer();

sunspec/integrationpluginsunspec.json

@@ -1472,6 +1472,14 @@
                             "writable": true,
                             "displayNameAction": "Set discharging rate"
                         },
+                        {
+                            "id": "ed738d23-4bea-40e9-a41e-ce6f37f1a3e2",
+                            "name": "controlHealthy",
+                            "displayName": "Control healthy",
+                            "displayNameEvent": "Control healthy changed",
+                            "type": "bool",
+                            "defaultValue": true
+                        },
                         {
                             "id": "47035ac0-d054-491a-969d-b2aaa9168b0a",
                             "name": "chargeGradient",
@@ -1751,6 +1759,91 @@
                     ]
                 }
             ]
+        },
+        {
+            "name": "fronius",
+            "displayName": "Fronius",
+            "id": "8504de60-2625-4ad4-8889-623a8d0453ff",
+            "thingClasses": [
+                {
+                    "name": "froniusConnection",
+                    "displayName": "Fronius",
+                    "id": "a4312ee8-ed15-4378-85e2-0372cef7de03",
+                    "createMethods": [ "discovery", "user" ],
+                    "interfaces": [ "gateway", "networkdevice" ],
+                    "providedInterfaces": [ "solarinverter", "energymeter", "energystorage" ],
+                    "discoveryParamTypes": [
+                        {
+                            "id": "c1d4df93-cc65-4766-a1b3-7c26edf986c0",
+                            "name":"slaveId",
+                            "displayName": "Slave ID",
+                            "type": "int",
+                            "defaultValue": 1
+                        }
+                    ],
+                    "paramTypes": [
+                        {
+                            "id": "bc8c1825-000b-401f-90c8-e70547041fca",
+                            "name": "address",
+                            "displayName": "Host address",
+                            "type": "QString",
+                            "inputType": "IPv4Address",
+                            "defaultValue": ""
+                        },
+                        {
+                            "id": "5882b8a7-2c83-4601-9dd4-e4cc5b5baed7",
+                            "name": "hostName",
+                            "displayName": "Host name",
+                            "type": "QString",
+                            "inputType": "TextLine",
+                            "defaultValue": ""
+                        },
+                        {
+                            "id": "9f16596f-1695-4112-bdca-df7207b4e30b",
+                            "name":"macAddress",
+                            "displayName": "MAC address",
+                            "type": "QString",
+                            "inputType": "MacAddress",
+                            "defaultValue": ""
+                        },
+                        {
+                            "id": "70ea61e2-18c3-4f82-a66c-6ed6876d3567",
+                            "name":"port",
+                            "displayName": "Port",
+                            "type": "int",
+                            "defaultValue": 502
+                        },
+                        {
+                            "id": "e8876609-cfad-4ebd-b998-d0b1b2dc5434",
+                            "name":"slaveId",
+                            "displayName": "Slave ID",
+                            "type": "int",
+                            "readOnly": true,
+                            "defaultValue": 1
+                        },
+                        {
+                            "id": "ad2ad84f-8513-4337-b7cf-fa45a9914a15",
+                            "name":"meterSlaveId",
+                            "displayName": "Smart Meter slave ID",
+                            "type": "int",
+                            "minValue": 0,
+                            "maxValue": 247,
+                            "defaultValue": 200
+                        }
+                    ],
+                    "stateTypes":[
+                        {
+                            "id": "d4cf07e1-6b53-47b6-9cab-7c7764023453",
+                            "name": "connected",
+                            "displayName": "Connected",
+                            "displayNameEvent": "Connected changed",
+                            "type": "bool",
+                            "defaultValue": false,
+                            "cached": false
+                        }
+                    ]
+                }
+            ]
         }
     ]
 }

sunspec/sunspec.pro

@@ -2,6 +2,7 @@ include(../plugins.pri)
 include(../sunspec.pri)
 
 SOURCES += \
+    froniusrules.cpp \
     integrationpluginsunspec.cpp \
     solaredgebattery.cpp \
     sunspecdiscovery.cpp \
@@ -9,6 +10,7 @@ SOURCES += \
     sunspecthing.cpp
 
 HEADERS += \
+    froniusrules.h \
     integrationpluginsunspec.h \
     solaredgebattery.h \
     sunspecdiscovery.h \