C# and C++ DLL file

Question

Hi,
I am currently trying to write a flash programmer uisng the SiUtil.dll file from Silicon Labs.
I am having problems when trying to read the scratchpad memory.
C++ Prototype: extern "C" __declspec(dllimport) int__stdcall GetScratchPadMemory(
BYTE * ptrMem, DWORD wStartAddress, unsigned int nLength);
C#
[DllImport(@"C:	emp\SiUtil.dll")]
public static extern int GetScratchPadMemory(ref byte Data, uint AddressToRead, uint Lenght);
I am sure there is some problems with how I declare this, but I do not know how to fix it.
I hope someone can guide me towards the correct way to do this.
Regards
John-Ove

John Larsen · Answer

Hi Vulpes,
I will try this first thing in the morning.

John Larsen · Answer

Hi,
Are you sure that there is a method GetScratchPadMemory with same signature what you have specified here?
Hi,
Well, I am not 100% sure because the datasheet does not talk about this function BUT in the source code they have supplied the function is there with the same signature. And I do not get an error when building the solution.
If the function had not been there I guess I would get an error message saying that this function has not been found in given DLL file?
Regards
John-Ove

Vulpes · Answer

I'm not familiar with that particular function but I'm guessing that you're specifying an offset into scratchpad memory (wStartAddress) and then asking the function to read nLength bytes from that address.
The function then passes back a pointer to the block of bytes to be read in the first parameter.
If that's the case, then I'd define your function as follows:
[DllImport(@"C:	emp\SiUtil.dll")] public static extern int GetScratchPadMemory(out IntPtr Data, uint AddressToRead, uint Length);
and call it like this:
IntPtr Data; uint AddressToRead = 0; // say int Length = 256; // say GetScratchPadMemory(out Data, AddressToRead, (uint)Length); byte[] bytes = new byte[Length]; Marshal.Copy(Data, bytes, 0, Length);

Jaganathan Bantheswaran · Answer

Hi,
Are you sure that there is a method GetScratchPadMemory with same signature what you have specified here?