How can I create a pointer to a structure with more than 3 elements?

Hello to eveyone. I am trying to write a MATLAB code able to use the DLL library of WaveVision5 from Texas Instruments, in order to control my ADC Development board. I am just trying now to call a function from the DLL, in order to see if the library is up and working.

Of course there is a little bit to have a look at what kind of data I will need, for example the function which I am trying to call is taking in input some kind of data defined inside the library header.

Now my function is taking in input: * A pointer to a ulong (which on my MATLAB should be a int32) * A pointer to a null terminated string * A pointer to a structure composed by four ulong.

typedef struct {
    /** Major */
    WvWord Major;

      /** Minor */
      WvWord Minor;

      /** Release */
      WvWord Release;

      /** Build */
      WvWord Build;
  } WvVersionNumber;

Now the problem is that I have created the first two pointers without problems, but it seems like I am not able to create a pointer to a structure containing more than 3 elements, for instance:

sm = struct('p1', int32(0), 'p2', int32(0), 'p3', int32(0), 'p4', int32(0));

sp = libpointer('c_struct',sm);

I receive the followind error:

A field does not match one in the struct.

Error in libpointer (line 18)
 ptr=lib.pointer(varargin{:});

Error in ADC_test (line 34)
sp = libpointer('c_struct',sm);

Instead if I just get rid of one of those fields inside the structure, everything looks fine.

I suppose that using c_struct is not the best way to do this, how can I create the wanted pointer? Any ideas?

Best Regards, Giovanni

[dpb]

I've not used libpointer but it says in the doc that

P = libpointer('TYPE') returns an empty pointer to the given TYPE.

TYPE can be any MATLAB numeric type, or a structure or enum defined in a loaded library.

From that I infer that the problem is that your sm is a Matlab structure and not one from a loaded library. Looks to me like you need

doc loadlibrary
doc libstruct

Answer 1

[Philip Borghesani]

dpb is correct the code should be something like:

% call loadlibrary to load mylib
sm = struct('Major', 0, 'Minor', 0, 'Release', 0, 'Build', 0) %let MATLAB worry about data types

verStruct=libstruct('WvVersionNumber',sm);
calllib('mylib','myfun', 0 ,'the string',verStruc);