diff --git a/knx-linux/main.cpp b/knx-linux/main.cpp
index 200c5c1..0a0bae9 100644
--- a/knx-linux/main.cpp
+++ b/knx-linux/main.cpp
@@ -1,6 +1,7 @@
 #include "knx_facade.h"
 #include "knx/bau57B0.h"
 #include "knx/group_object_table_object.h"
+#include "knx/bits.h"
 #include <time.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -9,9 +10,6 @@ LinuxPlatform platfrom;
 Bau57B0 bau(platfrom);
 KnxFacade knx(bau);
 
-float currentValue = 0;
-float maxValue = 0;
-float minValue = RAND_MAX;
 long lastsend = 0;
 
 #define CURR knx.getGroupObject(1)
@@ -22,35 +20,32 @@ long lastsend = 0;
 void measureTemp()
 {
     long now = platfrom.millis();
-    if ((now - lastsend) < 2000)
+    if ((now - lastsend) < 10000)
         return;
 
     lastsend = now;
     int r = rand();
-    currentValue = (r * 1.0) / (RAND_MAX * 1.0);
-    currentValue *= 100 * 100;
+    float currentValue = (r * 1.0) / (RAND_MAX * 1.0);
+    currentValue *= (670433.28 + 273);
+    currentValue -= 273;
+    println(currentValue);
+    CURR.value(currentValue);
 
-    CURR.objectWrite(currentValue);
+    double max = MAX.value();
+    if (currentValue > max)
+        MAX.value(currentValue);
 
-    if (currentValue > maxValue)
-    {
-        maxValue = currentValue;
-        MAX.objectWrite(maxValue);
-    }
-
-    if (currentValue < minValue)
-    {
-        minValue = currentValue;
-        MIN.objectWrite(minValue);
-    }
+    double min = MIN.value();
+    if (currentValue < MIN.value().doubleValue())
+        MIN.value(currentValue);
 }
 
 void resetCallback(GroupObject& go)
 {
-    if (go.objectReadBool())
+    if (go.value().boolValue())
     {
-        maxValue = 0;
-        minValue = 10000;
+        MAX.valueNoSend(-273.0);
+        MIN.valueNoSend(670433.28);
     }
 }
 
@@ -72,6 +67,12 @@ void setup()
 
     if (knx.configured())
     {
+        CURR.dataPointType(Dpt(9, 1));
+        MIN.dataPointType(Dpt(9, 1));
+        MIN.value(670433.28);
+        MAX.dataPointType(Dpt(9, 1));
+        MAX.valueNoSend(-273.0);
+        RESET.dataPointType(Dpt(1, 15));
         RESET.callback(resetCallback);
         printf("Timeout: %d\n", bau.parameters().getWord(0));
         printf("Zykl. senden: %d\n", bau.parameters().getByte(2));
diff --git a/src/knx/dptconvert.cpp b/src/knx/dptconvert.cpp
index e0d34cd..799e048 100644
--- a/src/knx/dptconvert.cpp
+++ b/src/knx/dptconvert.cpp
@@ -6,9 +6,10 @@
 #define ASSERT_PAYLOAD(x)      \
     if (payload_length != (x)) \
     return false
-#define ENSURE_PAYLOAD(x)            \
-    for (int pi = 0; pi < (x); ++pi) \
-    payload[pi] = 0
+#define ENSURE_PAYLOAD(x) 
+//\
+//    for (int pi = 0; pi < (x); ++pi) \
+//    payload[pi] = 0
 
 int KNX_Decode_Value(uint8_t* payload, int payload_length, const Dpt& datatype, KNXValue& value)
 {
@@ -1116,83 +1117,49 @@ int valueToBusValueTimeDelta(const KNXValue& value, uint8_t* payload, int payloa
 int valueToBusValueFloat16(const KNXValue& value, uint8_t* payload, int payload_length, const Dpt& datatype)
 {
     double numValue = value;
+
+    // bigger values like 670760.0 result in 0x7FFF which denotes invalid data.
+    // I'm not sure if the GO shouldn't be updated to this value instead
+    if (numValue > 670433.28)
+        return false;
+
+    if (numValue < -671088.64)
+        return false;
+
     switch (datatype.subGroup)
     {
         case 1:
-            if (numValue < -273.0 || numValue > 670760.0)
+            if (numValue < -273.0)
                 return false;
             break;
-        case 4:
-        case 7:
-        case 8:
-            if (numValue < 0.0 || numValue > 670760.0)
-                return false;
-            break;
-        case 5:
-        {
-            if (numValue < 0.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
-        case 6:
-        {
-            if (numValue < 0.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
-        case 10:
-        {
-            if (numValue < -670760.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
-        case 11:
-        {
-            if (numValue < -670760.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
-        case 20:
-        {
-            if (numValue < -670760.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
-        case 21:
-        {
-            if (numValue < -670760.0 || numValue > 670760.0)
-                return false;
-            break;
-        }
         case 2:
         case 3:
+        case 10:
+        case 11:
+        case 20:
+        case 21:
         case 22:
         case 23:
         case 24:
-            if (numValue < -670760.0 || numValue > 670760.0)
-                return false;
-            break;
         case 25:
-        {
-            if (numValue < -670760.0 || numValue > 670760.0)
+            if (numValue < -670760.0)
                 return false;
             break;
-        }
-        case 27:
-        {
-            if (numValue < -459.6)
-                return false;
-            break;
-        }
+        case 4:
+        case 5:
+        case 6:
+        case 7:
+        case 8:
         case 28:
             if (numValue < 0.0)
                 return false;
             break;
+        case 27:
+            if (numValue < -459.6)
+                return false;
+            break;
     }
 
-    if (numValue < -671088.64 || numValue > 670760.96)
-        return false;
-
     float16ToPayload(payload, payload_length, 0, numValue, 0xFFFF);
     return true;
 }
@@ -1819,9 +1786,20 @@ void signed32ToPayload(uint8_t* payload, int payload_length, int index, int32_t
 
 void float16ToPayload(uint8_t* payload, int payload_length, int index, double value, uint16_t mask)
 {
+    bool wasNegative = false;
+    if (value < 0)
+    {
+        wasNegative = true;
+        value *= -1;
+    }
+
     value *= 100.0;
-    unsigned short exponent = ceil(log2(value) - 10.0);
+    unsigned short exponent = ceil(log2(value) - 11.0);
     short mantissa = roundf(value / (1 << exponent));
+
+    if (wasNegative)
+        mantissa *= -1;
+
     signed16ToPayload(payload, payload_length, index, mantissa, mask);
     unsigned8ToPayload(payload, payload_length, index, exponent << 3, 0x78 & (mask >> 8));
 }
diff --git a/src/knx/dptconvert.h b/src/knx/dptconvert.h
index 83e6f34..219916f 100644
--- a/src/knx/dptconvert.h
+++ b/src/knx/dptconvert.h
@@ -35,7 +35,7 @@ class Dpt
 {
   public:
     Dpt() {}
-    Dpt(short mainGroup, short subGroup, short index) 
+    Dpt(short mainGroup, short subGroup, short index = 0) 
     {
         this->mainGroup = mainGroup;
         this->subGroup = subGroup;
diff --git a/src/knx/group_object.cpp b/src/knx/group_object.cpp
index 38fb85d..e1b9ef7 100644
--- a/src/knx/group_object.cpp
+++ b/src/knx/group_object.cpp
@@ -274,7 +274,7 @@ GroupObjectUpdatedHandler GroupObject::callback()
 
 void GroupObject::value(const KNXValue& value, const Dpt& type)
 {
-    KNX_Encode_Value(value, _data, _dataLength, type);
+    valueNoSend(value, type);
     objectWritten();
 }
 
@@ -320,3 +320,15 @@ KNXValue GroupObject::value()
 {
     return value(_datapointType);
 }
+
+
+void GroupObject::valueNoSend(const KNXValue& value)
+{
+    valueNoSend(value, _datapointType);
+}
+
+
+void GroupObject::valueNoSend(const KNXValue& value, const Dpt& type)
+{
+    KNX_Encode_Value(value, _data, _dataLength, type);
+}
diff --git a/src/knx/group_object.h b/src/knx/group_object.h
index 4ce1059..4734ddc 100644
--- a/src/knx/group_object.h
+++ b/src/knx/group_object.h
@@ -121,11 +121,14 @@ public:
     GroupObjectUpdatedHandler callback();
 
     KNXValue value(const Dpt& type);
-    void value(const KNXValue& value, const Dpt& type);
-    bool tryValue(KNXValue& value, const Dpt& type);
     KNXValue value();
+    void value(const KNXValue& value, const Dpt& type);
     void value(const KNXValue& value);
+    void valueNoSend(const KNXValue& value, const Dpt& type);
+    void valueNoSend(const KNXValue& value);
+    bool tryValue(KNXValue& value, const Dpt& type);
     bool tryValue(KNXValue& value);
+
     Dpt dataPointType();
     void dataPointType(Dpt value);
 
diff --git a/src/linux_platform.cpp b/src/linux_platform.cpp
index 541f7b5..ed763fd 100644
--- a/src/linux_platform.cpp
+++ b/src/linux_platform.cpp
@@ -488,6 +488,11 @@ void println(double num)
     printf("%f\n", num);
 }
 
+void println(double num, int places)
+{
+    printf("%f\n", num);
+}
+
 void println(void)
 {
     printf("\n");