Fix Sending Wrong Values on Failed Conversion to DPT

src/knx/group_object.cpp

@@ -226,8 +226,11 @@ GroupObjectUpdatedHandler GroupObject::callback()
 
 void GroupObject::value(const KNXValue& value, const Dpt& type)
 {
-    valueNoSend(value, type);
-    objectWritten();
+    if (_valueNoSend(value, type))
+    {
+        // write on successful conversion/setting value only
+        objectWritten();
+    }
 }
 
 
@@ -282,26 +285,40 @@ void GroupObject::valueNoSend(const KNXValue& value)
 
 void GroupObject::valueNoSend(const KNXValue& value, const Dpt& type)
 {
-    if (_commFlagEx.uninitialized)
+    // ignore actual updating TODO check replacing valueNoSend with _valueNoSend
+    _valueNoSend(value, type);
+}
+
+bool GroupObject::_valueNoSend(const KNXValue& value, const Dpt& type)
+{
+    const bool encodingDone = KNX_Encode_Value(value, _data, _dataLength, type);
+
+    // initialize on succesful conversion only
+    if (encodingDone && _commFlagEx.uninitialized)
         commFlag(Ok);
 
-    KNX_Encode_Value(value, _data, _dataLength, type);
+    return encodingDone;
 }
 
 bool GroupObject::valueNoSendCompare(const KNXValue& value, const Dpt& type)
 {
     if (_commFlagEx.uninitialized)
     {
         // always set first value
-        this->valueNoSend(value, type);
-        return true;
+        return _valueNoSend(value, type);
     }
     else
     {
-        // convert new value to given dtp
+        // convert new value to given DPT
         uint8_t newData[_dataLength];
         memset(newData, 0, _dataLength);
-        KNX_Encode_Value(value, newData, _dataLength, type);
+        const bool encodingDone = KNX_Encode_Value(value, newData, _dataLength, type);
+        if (!encodingDone)
+        {
+            // value conversion to DPT failed
+            // do NOT update the value of the KO!
+            return false;
+        }
 
         // check for change in converted value / update value on change only
         const bool dataChanged = memcmp(_data, newData, _dataLength);

src/knx/group_object.h

@@ -284,4 +284,15 @@ class GroupObject
     GroupObjectUpdatedHandler _updateHandler;
     Dpt _datapointType;
 #endif
+
+    /**
+     * set the current value of the group object and show success.
+     * @param value the value the group object is set to
+     * @param type the datapoint type used for the conversion.
+     * 
+     * The parameters must fit the group object. Otherwise it will stay unchanged.
+     * 
+     * @returns true if the value of the group object was updated after successful conversion.
+     */
+    bool _valueNoSend(const KNXValue& value, const Dpt& type);
 };