IEEE 754 floating numbers from Visual Basic to PIC microcont

[mabusoe]

ieee 754 vb6

I am trying to send a floating point number from VB to my C program runing on 16f876. In C I converted the IEE754 to a 4byte array, yet the Visual Basic does not have the same functions (UNION) is there some solution to transfer floating point number in byte format that is better?

Mabusoe

 

[kef]

ieee754 vb

Does VB have pointers? I think yes. Then try to convert
this

float a;

char a1,a2,a3,a4;

a1=*(char*)&a;
a2=*((char*)&a +1);
a3=*((char*)&a +2);
a4=*((char*)&a +3);

Compiled for little endian cpu a1 will contain lowest bits of mantissa and
a4 mantissa sign+7msb of biased exponent.

kef

 

[mabusoe]

visual basic convert double ieee binary

This is what I figured out for VB:


Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)

Private Sub SingleToIEEE754()

Dim bBytes(0 To 3) As Byte
Dim rMyNumber As Single
Dim i As Integer

rMyNumber = 333.7
Call CopyMemory(bBytes(0), rMyNumber, 4)

Debug.Print Hex$(bBytes(3)); " "; Hex$(bBytes(2)); " "; Hex$(bBytes(1)); " "; Hex$(bBytes(0))
End Sub

 

[mabusoe]

vb ieee 754

This is for C:

union FloatToChar
{
double fr; // 4 bytes as a long 32 bits.
unsigned char br[4]; // 4 bytes as 4 chars
};

union FloatToChar y;


Very nifty, luckily VB and the C compiler for the microcontroller use the same format for the 32bit floating point numbers