estoy usando el ejemplo de microchip para una FFT, soy nuevo en este asunto de los dsp, y segun el codigo, el resultado es guardado en la direccion 0x1C00 de la ram del dspic, hize una onda senoidal con el dspworks, y los resultados que salen los comparo con matlab, salen muy parecidos, ej, en matlab me sale 3.xxx en el dspic sale 1, luego en matlab sale 6, en el dsp sale 5, pero luego dan numeros inmensos que ya no entiendo porque salen, segun matlab debio de salir un numero cercano al 100, y en el dspic me sale 1070, tengo que realizar alguna conversion?, aqui esta el codigo fuente
#include <p30Fxxxx.h>
#include "dsp.h"
#include "fft.h"
/* Device configuration register macros for building the hex file */
_FOSC(CSW_FSCM_OFF & XT_PLL8); /* XT with 8xPLL oscillator, Failsafe clock off */
_FWDT(WDT_OFF); /* Watchdog timer disabled */
_FBORPOR(PBOR_OFF & MCLR_EN); /* Brown-out reset disabled, MCLR reset enabled */
_FGS(CODE_PROT_OFF); /* Code protect disabled */
/* Extern definitions */
extern fractcomplex sigCmpx[FFT_BLOCK_LENGTH] /* Typically, the input signal to an FFT */
__attribute__ ((section (".ydata, data, ymemory"), /* routine is a complex array containing samples */
aligned (FFT_BLOCK_LENGTH * 2 *2))); /* of an input signal. For this example, */
/* we will provide the input signal in an */
/* array declared in Y-data space. */
/* Global Definitions */
#ifndef FFTTWIDCOEFFS_IN_PROGMEM
fractcomplex twiddleFactors[FFT_BLOCK_LENGTH/2] /* Declare Twiddle Factor array in X-space*/
__attribute__ ((section (".xbss, bss, xmemory"), aligned (FFT_BLOCK_LENGTH*2)));
#else
extern const fractcomplex twiddleFactors[FFT_BLOCK_LENGTH/2] /* Twiddle Factor array in Program memory */
__attribute__ ((space(auto_psv), aligned (FFT_BLOCK_LENGTH*2)));
#endif
float salida;
int peakFrequencyBin = 0; /* Declare post-FFT variables to compute the */
unsigned long peakFrequency = 0; /* frequency of the largest spectral component */
int main(void)
{
int i = 0;
fractional *p_real = &sigCmpx[0].real ;
fractcomplex *p_cmpx = &sigCmpx[0] ;
#ifndef FFTTWIDCOEFFS_IN_PROGMEM /* Generate TwiddleFactor Coefficients */
TwidFactorInit (LOG2_BLOCK_LENGTH, &twiddleFactors[0], 0); /* We need to do this only once at start-up */
#endif
for ( i = 0; i < FFT_BLOCK_LENGTH; i++ )/* The FFT function requires input data */
{ /* to be in the fractional fixed-point range [-0.5, +0.5]*/
*p_real = *p_real >>1 ; /* So, we shift all data samples by 1 bit to the right. */
*p_real++; /* Should you desire to optimize this process, perform */
} /* data scaling when first obtaining the time samples */
/* Or within the BitReverseComplex function source code */
p_real = &sigCmpx[(FFT_BLOCK_LENGTH/2)-1].real ; /* Set up pointers to convert real array */
p_cmpx = &sigCmpx[FFT_BLOCK_LENGTH-1] ; /* to a complex array. The input array initially has all */
/* the real input samples followed by a series of zeros */
for ( i = FFT_BLOCK_LENGTH; i > 0; i-- ) /* Convert the Real input sample array */
{ /* to a Complex input sample array */
(*p_cmpx).real = (*p_real--); /* We will simpy zero out the imaginary */
(*p_cmpx--).imag = 0x0000; /* part of each data sample */
}
/* Perform FFT operation */
#ifndef FFTTWIDCOEFFS_IN_PROGMEM
FFTComplexIP (LOG2_BLOCK_LENGTH, &sigCmpx[0], &twiddleFactors[0], COEFFS_IN_DATA);
#else
FFTComplexIP (LOG2_BLOCK_LENGTH, &sigCmpx[0], (fractcomplex *) __builtin_psvoffset(&twiddleFactors[0]), (int) __builtin_psvpage(&twiddleFactors[0]));
#endif
/* Store output samples in bit-reversed order of their addresses */
BitReverseComplex (LOG2_BLOCK_LENGTH, &sigCmpx[0]);
/* Compute the square magnitude of the complex FFT output array so we have a Real output vetor */
SquareMagnitudeCplx(FFT_BLOCK_LENGTH, &sigCmpx[0], &sigCmpx[0].real);// <---- segun yo eso ya te lo convertia y te lo arrojaba en 0x1C00 por lo que indica el
puntero
while (1); /* Place a breakpoint here and observe the watch window variables */
}
