real time programming

i'm writing the code for real time computation of the supply for harmonics using dft.

to compute dft i have to take samples of the supply voltage but im not getting proper samples...can u help me with the part to take samples,this is the code

#include "xyz2cfg.h"
#include "c:\ccstudio_v3.1\c6000\dsk6713\include\dsk6713.h"
#include "c:\ccstudio_v3.1\c6000\dsk6713\include\dsk6713_aic23.h"

DSK6713_AIC23_Config config = { \
    0x0017,  /* 0 DSK6713_AIC23_LEFTINVOL  Left line input channel volume */ \
    0x0017,  /* 1 DSK6713_AIC23_RIGHTINVOL Right line input channel volume */\
    0x00d8,  /* 2 DSK6713_AIC23_LEFTHPVOL  Left channel headphone volume */  \
    0x00d8,  /* 3 DSK6713_AIC23_RIGHTHPVOL Right channel headphone volume */ \
    0x0011,  /* 4 DSK6713_AIC23_ANAPATH    Analog audio path control */      \
    0x0000,  /* 5 DSK6713_AIC23_DIGPATH    Digital audio path control */     \
    0x0000,  /* 6 DSK6713_AIC23_POWERDOWN  Power down control */             \
    0x0043,  /* 7 DSK6713_AIC23_DIGIF      Digital audio interface format */ \
    0x0081,  /* 8 DSK6713_AIC23_SAMPLERATE Sample rate control */            \
    0x0001   /* 9 DSK6713_AIC23_DIGACT     Digital interface activation */   \
};


/*
 *  main() - Main code routine, initializes BSL and generates tone
 */

void main()
{
 	int n=0,i=0;
	int a[8]={0,0,0,0,0,0,0,0};
    DSK6713_AIC23_CodecHandle hCodec;
  
    Uint32 l_input, r_input,l_output, r_output;
    
    /* Initialize the board support library, must be called first */
    DSK6713_init();
     
    /* Start the codec */
    hCodec = DSK6713_AIC23_openCodec(0, &config);
    	
    DSK6713_AIC23_setFreq(hCodec, 1);

    
       while(1)
        {	/* Read a sample to the left channel */
			while (!DSK6713_AIC23_read(hCodec, &l_input));
			
			if(n%25==0)
			{
			a[i++]=l_input;
				l_output=l_input;
				printf("\n%d",a[i-1]);
 		 	
			/* Send a sample to the left channel */
            while (!DSK6713_AIC23_write(hCodec, l_output));
			}
			
			if(i==7)
		{
		for(i=0;i<7;i++)
		{a[i]=a[i+1];
			i++;
}}			
			/* Read a sample to the right channel */
			while (!DSK6713_AIC23_read(hCodec, &r_input));          
				
			
        n++;

        }
   
    /* Close the codec */
    DSK6713_AIC23_closeCodec(hCodec);
}