Pass PByte to a DLL from vb..net - c++

Question

I having troubles to calling a function inside a C DLL (dont know if C or C++)
Basically, I m trying to make a wrapper for the SDK DLL of Gigabyte RGB Fusion API.
I m working in VB.NET with Visual Studio 2013 (if you answer in C# is good too)
Declaring functions with DLLImport
for Ex. This function works fine.
C++
int dllexp_GetMaxDivision(void)
VB.NET
<DllImport("GLedApi.dll", SetLastError:=False, callingConvention:=CallingConvention.Cdecl)> _
Public Shared Function dllexp_GetMaxDivision() As UInt32
EndFunction
calling dllexp_GetMaxDivision works like a charm. The trouble starts when i pass parameters:
DWORD dllexp_GetLedLayout(PBYTE bytArray, int arySize)
Parameters
Name / Type / Description
bytArray / Output / Pointer to a buffer that receives the LED layout on motherboard. The values of the elements in the array are as follows:
Value Meaning
0(NA) No implement LED
1(A_LED) Analog LED
2(D_LED_TYPE1) Digital LED Type 1
3(D_LED_TYPE2) Digital LED Type 2
arySize / Input / Size, in byte of the buffer indicated by bytArray. This value must be a dllexp_GetMaxDivision return value.
DWORD dllexp_SetLedData(PBYTE bytArray, int arySize)
Parameters
Name / Type / Description
bytArray / Input / Pointer to a byte array converted from the LEDSETTING
structure array.
arySize / Input / Size, in bytes, of the buffer indicated by bytArray.
typedef struct _LEDSETTING {
BYTE Reserve0;
BYTE LedMode;
BYTE MaxBrightness;
BYTE MinBrightness;
DWORD dwColor;
WORD wTime0;
WORD wTime1;
WORD wTime2;
BYTE CtrlVal0;
BYTE CtrlVal1;
} LEDSETTING, *PLEDSETTING
This is what I try. I dont get to test with dllexp_SetLedData yet, so I will focus in dllexp_GetLedLayout
<DllImport("GLedApi.dll", setLastError:=False, CallingConvention:=CallingConvention.Cdecl)> _
Public Shared Function dllexp_GetLedLayout(ByRef bytArray As IntPtr, arySize As Int32) As UInt32
End Function
Tried with a byte array, but didn't work. And This:
Dim Param(iMaxDivs - 1) As Byte
For A As Integer = 0 To iMaxDivs - 1
Param(A) = CByte(0)
Next
Dim Tama As Integer = Marshal.SizeOf(Param(0)) * Param.Length
Dim buffer As IntPtr = Marshal.AllocHGlobal(Tama)
Marshal.Copy(Param, 0, buffer, Param.Length)
resp2 = GLed.dllexp_GetLedLayout(buffer, Param.Length)
Marshal.Copy(buffer, Param, 0, Param.Length) '<===== AccessViolationException
Marshal.FreeHGlobal(buffer)
The line of code that retrieve the buffer to the array throw an exception:
'System.AccessViolationException' en mscorlib.dll Attempted to read or
write protected memory. This is often an indication that other memory
is corrupt.
In some other tests, i had PinvokeImbalance sort of... , I guess it was a type mismatch.
The weird thing is that sometimes, the code doesnt throw an exception and proceed, but return the zero-filled array. even when the buffer contains data.
I also try with AllocCoTaskMem but the process crash...,
Can somebody please point me in the right way to do this??
Thanks!