#dsk_app.c#

详细的OFDM设计过程

	    		DSK6713_LED_off(1);
	      		DSK6713_LED_off(0);
			}	
			break;
		case 2: 
			DSK6713_LED_toggle(0);
			if(nextFrame<(BUFFSIZE-FRAMELEN)){
				copyData(&databuf[startindex[0]+48], framebuffer, FRAMELEN);
				extractFrame(framebuffer, frameNumber, FRAMELEN);
				nextFrame = nextFrame+FRAMELEN;
				frameNumber++;
				state_r = 2;
			} else {  // Fucking bastards! The frame overlaps the buffer borders..
				copyData(&databuf[startindex[0]+48], framebuffer, (BUFFSIZE-startindex[0]-48));
				nextFrame = FRAMELEN-(BUFFSIZE-nextFrame);	
				state_r = 3;
			}
			break;
		
		case 3: 		// Buffer begins with a half frame..
			DSK6713_LED_toggle(0);
			copyData(databuf, &framebuffer[FRAMELEN-nextFrame], (nextFrame-1));
			extractFrame(framebuffer, frameNumber, FRAMELEN);
			frameNumber++;
			state_r = 2;
			break;
		case 4:
			DSK6713_LED_toggle(0);
			// All frames are recieved.. Kill all..
			break;
	}
	
	state_r=1;


	framesync(databuf, startindex, length);
	
//	energydetect(databuf, startindex, length);
//	slask = startindex[0] - loopIndex;
	
	if(startindex[0] != 0)
	{
		if((RefIndex+10)==startindex[0]) 
		   	DSK6713_LED_toggle(1);
	
		//if(((loopIndex-10)<startindex[0]) && ((loopIndex+40)>startindex[0]))
    	if((loopIndex+17)==startindex[0]) 
    		DSK6713_LED_toggle(0);
/*    DSK6713_LED_on(1);
	while(1){
		DSK6713_LED_toggle(0);
//		 createTrig(ProcessBuffer, BUFFSIZE);      
        /* Copy receive PING buffer to transmit PING buffer */
//	     copyData2x2(ProcessBuffer, gBufferXmtPong, BUFFSIZE);		


//	}	*/
		RefIndex = startindex[0];
	} else {
	      DSK6713_LED_off(1);
	      DSK6713_LED_off(0);
	}	
	

	// Call next syncronization funktion
//	sync(float *in , const float *training_seq)	
	
	// Decode the frame here:
	// Call downsample
	// Call demodulation
	// Call deinterleaving
	// Call deconvolution
	
	   		
}

void extractFrame(short *framebuffer, short frameNumber, short length)
{
	state_r = 1;

}

/*
 *  copy2Data() - Copy one buffer with length elements to another.
 *  And remove every second value. 
 */
void copy2Data(short *inbuf, short *outbuf, short length)
{	// length is length of outbuffer, == 1/2 inbuf
    short i = 0;
    
    for (i = 0; i < length; i++) {                      
        outbuf[i]  = inbuf[i*2];
    }
}
/*
 *  copyData2x2() - Copy one buffer with length elements to another.
 *  And remove every second value. 
 */
void copyData2x2(short *inbuf, short *outbuf, short length)
{	// length is length of inbuffer, == 1/2 outbuf
    short i = 0;
    
    for (i = 0; i < length; i++) {                      
        outbuf[i*2]  = inbuf[i];
    }
}

void createTrig(short *databuf, const short length)
{

	short i, k=0;
	
	// Length of sine wave table *
	const short sin_size = 48; //  72

	// Pre-generated sine wave data, 16-bit signed samples *
	short sinetable[ ] = {
    	0x0000, 0x10b4, 0x2120, 0x30fb, 0x3fff, 0x4dea, 0x5a81, 0x658b,
    	0x6ed8, 0x763f, 0x7ba1, 0x7ee5, 0x7ffd, 0x7ee5, 0x7ba1, 0x76ef,
    	0x6ed8, 0x658b, 0x5a81, 0x4dea, 0x3fff, 0x30fb, 0x2120, 0x10b4,
    	0x0000, 0xef4c, 0xdee0, 0xcf06, 0xc002, 0xb216, 0xa57f, 0x9a75,
    	0x9128, 0x89c1, 0x845f, 0x811b, 0x8002, 0x811b, 0x845f, 0x89c1,
    	0x9128, 0x9a76, 0xa57f, 0xb216, 0xc002, 0xcf06, 0xdee0, 0xef4c
	};  
	
/*	short sinetable[ ] = {
		0, 		5328, 	10714, 	15982, 	20926, 	25317, 	28906, 	31441, 
		32681, 	32412, 	30479, 	26805, 	21422, 	14496, 	6346, 	-2546, 
		-11545, -19888, -26739, -31270, -32762, -30732, -25057, -16084, 
		-4688, 	7733, 	19377, 	28262, 	32571, 	31054, 	23444, 	10743, 
		-4705, 	-19503, -29864, -32600, -26223, -11813, 6756, 	23554, 
		32371, 	29125, 	14059, 	-7402, 	-26064, -32705, -22915, -579
	};
*/
/*	short sinetable[ ] = {
	0,		2207,	4404,	6580,8,	8727,7,	10835,	12892,	14891,
	16822,	18676,	20445,	22121,	23696,	25163,	26515,	27746,
	28851,	29824,	30661,	31358,	31912,	32321,	32582,	32695,
	32659,	32473,	32140,	31660,	31035,	30269,	29366,	28328,
	27160,	25870,	24461,	22940,	21315,	19593,	17781,	15888,
	13923,	11894,	9811,3,	7683,6,	5520,9,	3332,9,	1129,8,	-1078,5  };
*/
/*	short sinetable[ ] = {
		0,	3701,	7460,	11222,	14924,	18495,	21857,	24925,
		27612,	29828,	31481,	32485,	32760,	32237,	30865,	28614,
		25478,	21486,	16703,	11233,	5222,	-1138,	-7616,	-13944,
		-19826,	-24949,	-29001,	-31688,	-32758,	-32026,	-29398,	-24897,
		-18676,	-11038,	-2431,	6564,	15258,	22902,	28751,	32136,
		32554,	29747,	23777,	15077,	4456,	-6939,	-17721,	-26420,
		-31684,	-32509,	-28463,	-19847,	-7777,	5894,	18799,	28440,
		32688,	30302,	21350,	7416,	-8547,	-22744,	-31409,	-31852,
		-23414,	-7985,	10178,	25468,	32625,	28651,	14279,	0			};
*/
	
//	int j;
	loopIndex += 10;
	if(loopIndex>400)
		loopIndex=100;

	for(i=0; i<BUFFSIZE; i++)
		databuf[i]=0;
	for(i=loopIndex; i<(loopIndex+sin_size); i++)
		{
			databuf[i]=sinetable[k];
			k++;
		}
}

void energydetect(const short *databuf, short *startindex, const short length)
{
	short i,k;
	int sum;
	startindex[0] = 0;
	for(i=0; i<length-10; i+=5)
	{
		sum = 0;
		for(k=0; k<10; k++)
			sum += databuf[k+i]*databuf[k+i];
		if(sum>treshold){					// Find a good detection threshold. 
			startindex[0]=i;	
			break;
		}
	}
}

void framesync(short *databuf, short *startindex, short length)
{
	// The databuf might contain a trigger signal, the same as the defined sinetable here. 

	/* Length of sine wave table */
	const short sin_size = 48;   // 72

	/* Pre-generated sine wave data, 16-bit signed samples */
	const short sinetable[ ] = {
    	0x0000, 0x10b4, 0x2120, 0x30fb, 0x3fff, 0x4dea, 0x5a81, 0x658b,
    	0x6ed8, 0x763f, 0x7ba1, 0x7ee5, 0x7ffd, 0x7ee5, 0x7ba1, 0x76ef,
    	0x6ed8, 0x658b, 0x5a81, 0x4dea, 0x3fff, 0x30fb, 0x2120, 0x10b4, 
    	0x0000, 0xef4c, 0xdee0, 0xcf06, 0xc002, 0xb216, 0xa57f, 0x9a75,
    	0x9128, 0x89c1, 0x845f, 0x811b, 0x8002, 0x811b, 0x845f, 0x89c1,
    	0x9128, 0x9a76, 0xa57f, 0xb216, 0xc002, 0xcf06, 0xdee0, 0xef4c 	};

/*	short sinetable[ ] = {
	0,		2207,	4404,	6580,8,	8727,7,	10835,	12892,	14891,
	16822,	18676,	20445,	22121,	23696,	25163,	26515,	27746,
	28851,	29824,	30661,	31358,	31912,	32321,	32582,	32695,
	32659,	32473,	32140,	31660,	31035,	30269,	29366,	28328,
	27160,	25870,	24461,	22940,	21315,	19593,	17781,	15888,
	13923,	11894,	9811,3,	7683,6,	5520,9,	3332,9,	1129,8,	-1078,5  };
*/

/*	short sinetable[ ] = {
		0, 		5328, 	10714, 	15982, 	20926, 	25317, 	28906, 	31441, 
		32681, 	32412, 	30479, 	26805, 	21422, 	14496, 	6346, 	-2546, 
		-11545, -19888, -26739, -31270, -32762, -30732, -25057, -16084, 
		-4688, 	7733, 	19377, 	28262, 	32571, 	31054, 	23444, 	10743, 
		-4705, 	-19503, -29864, -32600, -26223, -11813, 6756, 	23554, 
		32371, 	29125, 	14059, 	-7402, 	-26064, -32705, -22915, -579	};
*/
/*	short sinetable[ ] = {
		0,	3701,	7460,	11222,	14924,	18495,	21857,	24925,
		27612,	29828,	31481,	32485,	32760,	32237,	30865,	28614,
		25478,	21486,	16703,	11233,	5222,	-1138,	-7616,	-13944,
		-19826,	-24949,	-29001,	-31688,	-32758,	-32026,	-29398,	-24897,
		-18676,	-11038,	-2431,	6564,	15258,	22902,	28751,	32136,
		32554,	29747,	23777,	15077,	4456,	-6939,	-17721,	-26420,
		-31684,	-32509,	-28463,	-19847,	-7777,	5894,	18799,	28440,
		32688,	30302,	21350,	7416,	-8547,	-22744,	-31409,	-31852,
		-23414,	-7985,	10178,	25468,	32625,	28651,	14279,	0			};
*/
	
	int res[2];
	
	correlation(sinetable, databuf, sin_size, length, res);
	
	startindex[0] = res[1];
	
	if(res[0] < 1000000)		// is the correlation over minimum treshold. 
		startindex[0] = 0;
}

void correlation(const short *reference, const short *input, const short len_ref, const short len_inp, int *res)
{
	short i,k;
	int sum;
	res[0]=0;
	for (i = 0; i < (len_inp - len_ref); i++){
		sum = 0;
//		slask=0;
		for (k = i; k < (len_ref+i); k++){
			sum = sum + (((input[k]/0x10) * (reference[k-i]/0x10)));
			if(sum<-10000)
				break;
		}
		if(res[0]<(sum))			// Find and store the point with largest correlation. 
		{
			res[0] = (sum);
			res[1] = i;
		}
	}
}

/*
 *  blinkLED() - Periodic thread (PRD) that toggles LED #0 every 500ms if 
 *               DIP switch #0 is depressed.  The thread is configured
 *               in the DSP/BIOS configuration tool under Scheduling -->
 *               PRD --> PRD_blinkLed.  The period is set there at 500
 *               ticks, with each tick corresponding to 1ms in real
 *               time.
 */
void blinkLED(void)
{
    /* Toggle LED #0 if DIP switch #0 is off (depressed) */
    if (!DSK6713_DIP_get(0))
        DSK6713_LED_toggle(0);
}


/*
 *  load() - PRD that simulates a 20-25% dummy load on a 225MHz 6713 if
 *           DIP switch #1 is depressed.  The thread is configured in
 *           the DSP/BIOS configuration tool under Scheduling --> PRD
 *           PRD_load.  The period is set there at 10 ticks, which each tick
 *           corresponding to 1ms in real time.
 */
void load(void)
{
    volatile Uint32 i;  

    if (!DSK6713_DIP_get(1))
        for (i = 0; i < 30000; i++);
}