Add float type support to Parameters

All 3 encodings supported.

src/knx/application_program_object.cpp

@@ -47,3 +47,26 @@ uint32_t ApplicationProgramObject::getInt(uint32_t addr)
 {
     return ::getInt(TableObject::data() + addr);
 }
+
+double ApplicationProgramObject::getFloat(uint32_t addr, ParameterFloatEncodings encoding)
+{
+    uint8_t buffer[8];
+    switch (encoding)
+    {
+        case Float_Enc_DPT9:
+            memcpyInverted(buffer, TableObject::data() + addr, 2);
+            return Decode_DPT9_Float(*(uint16_t*)buffer);
+            break;
+        case Float_Enc_IEEE754Single:
+            memcpyInverted(buffer, TableObject::data() + addr, 4);
+            return *(float*)(buffer);
+            break;
+        case Float_Enc_IEEE754Double:
+            memcpyInverted(buffer, TableObject::data() + addr, 8);
+            return *(double*)(buffer);
+            break;
+        default:
+            return 0;
+            break;
+    }
+}

src/knx/application_program_object.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "table_object.h"
+#include "bits.h"
 
 class ApplicationProgramObject : public TableObject
 {
@@ -10,4 +11,5 @@ class ApplicationProgramObject : public TableObject
     uint8_t getByte(uint32_t addr);
     uint16_t getWord(uint32_t addr);
     uint32_t getInt(uint32_t addr);
+    double getFloat(uint32_t addr, ParameterFloatEncodings encoding);
 };

src/knx/bits.cpp

@@ -107,6 +107,31 @@ uint64_t sixBytesToUInt64(uint8_t* data)
     return l;
 }
 
+const uint16_t eMask = 0x7800; //01111000 00000000
+const uint16_t mMask = 0x87FF; //10000111 11111111
+const uint16_t sMask = 0x8000; //10000000 00000000
+
+float Decode_DPT9_Float(uint16_t n)
+{
+    uint16_t e = n & eMask;
+    uint16_t m = n & mMask;
+    int16_t sm = m;
+    if (m & sMask)
+    {
+        m = (~m & mMask) + 1;
+        sm = -(int)m;
+    }
+    return (0.01 * (float)sm) * pow(2, e);
+}
+
+void memcpyInverted(uint8_t* dst, uint8_t* src, size_t length)
+{
+    for (int i = 0; i < length; i++)
+    {
+        dst[i] = src[length - i - 1];
+    }
+}
+
 // The CRC of the Memory Control Block Table Property is a CRC16-CCITT with the following
 // parameters:
 // Width = 16 bit

src/knx/bits.h

@@ -92,3 +92,13 @@ void sixBytesFromUInt64(uint64_t num, uint8_t* toByteArray);
 uint64_t sixBytesToUInt64(uint8_t* data);
 
 uint16_t crc16Ccitt(uint8_t* input, uint16_t length);
+
+enum ParameterFloatEncodings
+{
+    Float_Enc_DPT9 = 0,          // 2 Byte. See Chapter 3.7.2 section 3.10 (Datapoint Types “2-Octet Float Value”)
+    Float_Enc_IEEE754Single = 1, // 4 Byte. C++ float
+    Float_Enc_IEEE754Double = 2, // 8 Byte. C++ double
+};
+
+float Decode_DPT9_Float(uint16_t n);
+void memcpyInverted(uint8_t* dst, uint8_t* src, size_t length);

src/knx_facade.h

@@ -268,6 +268,14 @@ template <class P, class B> class KnxFacade : private SaveRestore
         return _bau.parameters().getInt(addr);
     }
 
+    double paramFloat(uint32_t addr, ParameterFloatEncodings enc)
+    {
+        if (!_bau.configured())
+            return 0;
+
+        return _bau.parameters().getFloat(addr, enc);
+    }
+    
 #if (MASK_VERSION == 0x07B0) || (MASK_VERSION == 0x27B0) || (MASK_VERSION == 0x57B0)
     GroupObject& getGroupObject(uint16_t goNr)
     {