Win32Api USB SetupDiGetDeviceInterfaceDetail fail

Question

I am attempting to connect to a USB GPS device. I can successfully connect to the device if I manually create a file via CreateFile WinApi (using the path specified in Devi

Answer 1

I believe I found the problem.

After poking around pinvoke.net, I found the following

// build a Device Interface Detail Data structure
 SP_DEVICE_INTERFACE_DETAIL_DATA didd = new SP_DEVICE_INTERFACE_DETAIL_DATA();
 if (IntPtr.Size == 8) // for 64 bit operating systems
     didd.cbSize = 8; 
 else  didd.cbSize = 4 + Marshal.SystemDefaultCharSize; // for 32 bit systems

Changing this in my code allows me to obtain the DevicePath properly.

Reference for those interested.

http://pinvoke.net/default.aspx/setupapi.SetupDiGetDeviceInterfaceDetail

Answer 2

Congratulations, it is working. You'll get a Unicode string, it's twice as long. And a FALSE return is correct. You just need to call Marshal.GetLastWin32Error() and verify that you got ERROR_INSUFFICIENT_BUFFER. Your C code is broken, probably because you forgot to initialize theBytesReturned to zero.