Hi

I need to move "floats" (single precision) between a C# application in
a PC and a C++ program running on an embedded system. The C++ program
has been compiled with Rowley Associates CrossStudio 1.7 build 4,
which uses GNU C/C++ compiler GCC, and runs on an NXP LPC2103 with
ARM7 core.

On the C++ side, I have no problems sending/receiving floats. It is on
the C# side, where I have problems trying to imitate what in C++ is a
union.

I have tried the following:
// ...................................................
// These "using" are the C# equivalent ones to "typedef" in C++.
using u08        =System.Byte;
using u16        =System.UInt16;
using u32        =System.UInt32;
using u64        =System.UInt64;

using i08        =System.SByte;
using i16        =System.Int16;
using i32        =System.Int32;
using i64        =System.Int64;
// ...................................................
[StructLayout(LayoutKind.Explicit)]
public    struct S_u08_flo
{
    [FieldOffset(0)]
    public float            flo;
    [FieldOffset(0)]
    public u08[]            u08_array;
}
// ...................................................
// float  = single precision IEEE floating point (4 bytes)
public    float ReadData_flo()
{
    S_u08_flo                u;
    u.u08_array                =new u08[4];
    u.flo                    =0.0F;
    for (int i=0;i<4;i++)
    {
        u.u08_array[i]=u08_data[u16_idx++];
    } // for
    return(u.flo);
}
// ...................................................
// float  = single precision IEEE floating point (4 bytes)
public    void WriteData_flo(float flo_data)
{
    S_u08_flo                u;
    u.u08_array                =new u08[4];
    u.flo                    =flo_data;
    for (int i=0;i<4;i++)
    {
        u08_data[u16_idx++]=u.u08_array[i];
    } // for
}
// ...................................................

and it compiles ok but, at run time, it says

// ...................................................
System.TypeLoadException was unhandled
 Message="Could not load type 'S_u08_flo' from assembly 'Pyramid_USB,
Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' because it
contains an object field at offset 0 that is incorrectly aligned or
overlapped by a non-object field."
 Source="Pyramid_USB"
 TypeName="S_u08_flo"
 StackTrace:
      at N_Pyramid.C_PKT2.ReadData_flo()
// ...................................................

Any hint on what may I be doing wrong? It looks like it is complaining
about the overlapping between the two fields in the structure, but I
do need that overlapping to simulate a union.

Or, is there any other way in C# to convert {4 bytes} <---> {1 float}
?

Thank you very much,
Jon