Managed dll import complaining about string marshalling

Hi Alex,

I just ran into the same issue when trying to use a managegd DAQ library (MccDaq/Meilhaus) inside of Unity. Have you made any progress on this issue?

Kind regards, claus

I never got the managed dll to work. I don't remember why, it was either because Unity doesn't like even managed dlls calling other dlls or something to do with the compiler they used. I ended up using the native 64 bit dll. This is the class I used to wrap it:

 using UnityEngine;
 using System.Collections;
 using System.Runtime.InteropServices;
 
 // This class wraps up the MCDAQ dll.  This is the library that lets us set the 
 // voltage of our device
 
 //TODO error checking for cb calls
 
 public class MCDAQ
 {    
 //------------------------------------------------------------------------CONSTANTS:
 
     private const string LOG_TAG = "MCDAQ";
     private const bool VERBOSE = false;
 
     // Types of configuration
     private static int GLOBALINFO = 1;
     private static int BOARDINFO = 2;
 
     // Types of board configuration info
     private static int BIRANGE    = 6;    // Switch selectable range
     private static int BICLOCK    = 5;    // Switch selectable range
 
     // Available ranges
     private static int BIP10VOLTS = 1;        // -10 to +10 Volts
     private static int BIP5VOLTS  = 0;        // -5 to +5 Volts
     private static int UNI10VOLTS = 100;    // 0 to +10 Volts
 
     // Types of error reporting
     private static int DONTPRINT = 0;
     private static int PRINTALL  = 3;     
 
     // Types of error handling
     private static int DONTSTOP = 0;
     private static int STOPALL = 2;       
 
     private static float CURRENT_REVISION_NUMBER = 6.51f;
     private static int BOARD_NUMBER = 0;
     private static int RANGE         = BIP10VOLTS;
     private static int CHANNEL         = 0;
 
 //---------------------------------------------------------EXTERNAL METHODS IMPORTS:
 
     [DllImport( "cbw64" )]
     private static extern int cbDeclareRevision( ref float revisionNumber );
 
     [DllImport( "cbw64" )]
     private static extern int cbAOut( int boardNumber, 
                                       int channel, 
                                       int gain, 
                                       ushort dataValue );
 
     [DllImport( "cbw64" )]
     private static extern int cbErrHandling( int reporting, int handling );
 
     [DllImport( "cbw64" )]
     private static extern int cbFlashLED( int boardNumber );
 
     [DllImport( "cbw64" )]
     private static extern int cbFromEngUnits( int boardNumber, 
                                               int range,
                                               float engineeringUnits,
                                               out ushort dataValue );
 
     [DllImport( "cbw64" )]
     private static extern int cbGetConfig( int infoType,
                                            int boardNumber,
                                            int deviceNumber,
                                            int configurationItem,
                                            out int configurationValue );
     
     [DllImport( "cbw64" )]
     private static extern int cbSetConfig( int infoType,
                                            int boardNumber,
                                            int deviceNumber,
                                            int configurationItem,
                                            int configurationValue );
     
     [DllImport( "cbw64" )]
     private static extern int cbVOut( int boardNumber, 
                                       int channel, 
                                       int range, 
                                       float dataValue,
                                       int options );
     
 //---------------------------------------------------------------------------FIELDS:    
     
     private static bool isInitialized;
 
 //--------------------------------------------------------------------------METHODS:
 
     public static void flashLED()
     {
         cbFlashLED( BOARD_NUMBER );
     }
         
     public static void init()
     {
         // Declare the current software version
         float revisionNum = CURRENT_REVISION_NUMBER;
         cbDeclareRevision( ref revisionNum );
         // Specify internal error handling
         cbErrHandling( PRINTALL, DONTSTOP );
         
         isInitialized = true;
     }
 
     public static void writeVolts( float volts )
     {
         ushort dataValue;
         if( VERBOSE )
         {
             Utility.print(LOG_TAG, "Writing Volts: " + volts);
         }
         // Go from pos/neg volts to unsigned int
         cbFromEngUnits( BOARD_NUMBER, RANGE, volts, out dataValue );
         // Send signal to actuate
         cbAOut( BOARD_NUMBER, CHANNEL, RANGE, dataValue );
     }
 }