dsp.h

dsPIC33F单片机的ADC采样以及IIR数字滤波的应用范例代码

   					/* (y[n], 0 <= n < N) */
   fractional* srcSamps,		/* ptr to input samples */
   					/* (x[n], 0 <= n < N) */
   IIRTransposedStruct* filter		/* Transposed biquad filter structure */

   					/* returns dstSamps */
);

extern void IIRTransposedInit (		/* Initialize filter structure */
   IIRTransposedStruct* filter		/* Transposed biquad filter structure */
);

/* ....................................................................... */

typedef struct {
   int order;				/* filter order (M) */
   					/* M <= N (see IIRLattice for N) */
   fractional* kappaVals;		/* ptr to lattice coefficients */
   					/* (k[m], 0 <= m <= M) */
					/* either in X-Data or P-MEM */
   fractional* gammaVals;		/* ptr to ladder coeficients */
   					/* (g[m], 0 <= m <= M) */
					/* either in X-Data or P-MEM */
   					/* NULL for all pole implementation */
   int coeffsPage;			/* page number of program memory if */
					/* coefficients are in program memory */
					/* COEFFS_IN_DATA if not */
   fractional* delay;			/* ptr to delay */
   					/* (d[m], 0 <= m <= M) */
					/* only in Y-Data */
} IIRLatticeStruct;			/* IIR Lattice filter structure */

extern fractional* IIRLattice (		/* IIR Lattice filtering */
   int numSamps,			/* number of input samples (N) */
   fractional* dstSamps,		/* ptr to output samples */
   					/* (y[n], 0 <= n < N) */
   fractional* srcSamps,		/* ptr to input samples */
   					/* (x[n], 0 <= n < N) */
   IIRLatticeStruct* filter		/* filter structure */

   					/* returns dstSamps */
);

extern void IIRLatticeInit (		/* Zero out dealy in filter structure */
   IIRLatticeStruct* filter		/* Lattice filter structure */
);

/* ....................................................................... */

/****************************************************************************
*
* Interface to transform operations.
*
* A set of linear discrete signal transformations (and some of the inverse
* transforms) are prototyped below. The first set applies a Discrete Fourier
* transform (or its inverse) to a complex data set. The second set applies
* a Type II Discrete Cosine Transform (DCT) to a real valued sequence.
*
* A complex valued sequence is represented by a vector in which every pair
* of values corresponds with a sequence element. The first value in the pair
* is the real part of the element, and the second its imaginary part (see
* the declaration of the 'fractcomplex' structure at the beginning of this
* file for further details). Both, the real and imaginary parts, are stored
* in memory using one word (two bytes) each, and must be interpreted as Q.15
* fractionals.
*
* The following transforms have been designed to either operate out-of-place,
* or in-place. The former type populates an output sequence with the results
* of the transformation. In the latter, the input sequence is (physically)
* replaced by the transformed sequence. For out-of-place operations, the user
* must provide with enough memory to accept the results of the computation.
* The input and output sequences to the FFT family of transforms must be
* allocated in Y-Data memopry.
*
* The transforms here described make use of transform factors which must be
* supplied to the transforming function during its invokation. These factors,
* which are complex data sets, are computed in floating point arithmetic,
* and then transformed into fractionals for use by the operations. To avoid
* excessive overhead when applying a transformation, and since for a given
* transform size the values of the factors are fixed, a particular set of
* transform factors could be generated once and used many times during the
* execution of the program. Thus, it is advisable to store the factors
* returned by any of the initialization operations in a permanent (static)
* vector. The factors to a transform may be allocated either in X-Data or
* program memory.
*
* Additional remarks.
*
* A) Operations which return a destination vector can be nested, so that
*    for instance if:
*
*	a = Op1 (b, c), with b = Op2 (d), and c = Op3 (e, f), then
*
*	a = Op1 (Op2 (d), Op3 (e, f))
*
****************************************************************************/

/* Transform operation prototypes. */


extern fractcomplex* TwidFactorInit (	/* Initialize twiddle factors */
					/* WN(k) = exp(i*2*pi*k/N) */
					/* computed in floating point */
					/* converted to fractionals */
   int log2N,				/* log2(N), N complex factors */
   					/* (although only N/2 are computed */
   					/* since only half of twiddle factors */
					/* are used for I/FFT computation) */
   fractcomplex* twidFactors,		/* ptr to twiddle factors */
   int conjFlag				/* indicates whether to generate */
					/* complex conjugates of twiddles */
					/* 0 : no conjugates (default) */
					/* 1 : conjugates */

					/* twidfact returned */
					/* only the first half: */
					/* WN(0)...WN(N/2-1) */
					/* (or their conjugates) */
);

/*...........................................................................*/

extern fractcomplex* BitReverseComplex (	/* Bit Reverse Ordering */
					/* (complex) */
   int log2N,				/* log2(N), N is vector length */
   fractcomplex* srcCV			/* ptr to source complex vector */
					/* MUST be N modulo aligned */

					/* srcCV returned */
);

/*...........................................................................*/

extern fractcomplex* FFTComplex (	/* Fast Fourier Transform */
					/* (complex, out-of-place) */
   int log2N,				/* log2(N), N-point transform */
   fractcomplex* dstCV,			/* ptr to destination complex vector */
   					/* with time samples */
					/* in natural order */
					/* MUST be N modulo aligned */
   fractcomplex* srcCV,			/* ptr to source complex vector */
   					/* with time samples */
					/* in natural order */
   fractcomplex* twidFactors,		/* base address of twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* dstCV returned */
   					/* with frequency components */
					/* in natural order */
					/* and scaled by 1/(1<<log2N) */
);

/*...........................................................................*/

extern fractcomplex* FFTComplexIP (	/* Fast Fourier Transform */
					/* (complex, in-place) */
   int log2N,				/* log2(N), N-point transform */
   fractcomplex* srcCV,			/* ptr to source complex vector */
   					/* with time samples */
					/* in natural order */
   fractcomplex* twidFactors,		/* base address of twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* srcCV returned */
   					/* with frequency components */
					/* in bit reverse order */
					/* and scaled by 1/(1<<log2N) */
);

/*...........................................................................*/

extern fractcomplex* IFFTComplex (	/* Inverse Fast Fourier Transform */
					/* (complex, out-of-place) */
   int log2N,				/* log2(N), N-point transform */
   fractcomplex* dstCV,			/* ptr to destination complex vector */
   fractcomplex* srcCV,			/* ptr to source complex vector */
   					/* with frequency components */
					/* in natural order */
					/* MUST be N modulo aligned */
   fractcomplex* twidFactors,		/* base address of twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* dstCV returned */
   					/* with time samples */
					/* in natural order */
);

/*...........................................................................*/

extern fractcomplex* IFFTComplexIP (	/* Inverse Fast Fourier Transform */
					/* (complex, in-place) */
   int log2N,				/* log2(N), N-point transform */
   fractcomplex* srcCV,			/* ptr to source complex vector */
   					/* with frequency components */
					/* in bit reverse order */
					/* MUST be N modulo aligned */
   fractcomplex* twidFactors,		/* base address of twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* srcCV returned */
   					/* with time samples */
					/* in natural order */
);

/*...........................................................................*/

extern fractcomplex* CosFactorInit (	/* Initialize cosine factors */
					/* CN(k) = exp(i*k*pi/(2*N)) */
					/* computed in floating point */
					/* converted to fractionals */
   int log2N,				/* log2(N), N complex factors */
   					/* (although only N/2 are computed */
   					/* since only half of cosine factors */
					/* are used for DCT computation) */
   fractcomplex* cosFactors		/* ptr to cosine factors */

					/* cosineFactors returned */
					/* only the first half: */
					/* CN(0)...CN(N/2-1) */
);

/*...........................................................................*/

extern fractional* DCT (		/* Type II Discrete Cosine Transform */
					/* (out-of-place) */
   int log2N,				/* log2(N), N is transform length */
   fractional* dstV,			/* ptr to destination vector (2*N) */
   					/* (transform in first N samples) */
					/* MUST be N modulo aligned */
   fractional* srcV,			/* ptr to source vector (N) in Y-Data */
   					/* MUST be zero padded to length 2*N */
   fractcomplex* cosFactors,		/* base address of cosine factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* CN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
					/* a total of N/2 complex values: */
					/* CN(k) = exp(i*k*pi/(2*N)) */
					/* CN(0)...CN(N/2-1) */
   fractcomplex* twidFactors,		/* base address of complex conjugate */
   					/* twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
					/* a total of N/2 complex values: */
					/* WN(k) = exp(-i*2*pi*k/N) */
					/* WN(0)...WN(N/2-1) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* Both, cosine and twiddle factors, */
					/* MUST be allocated in the same */
					/* memory space: both in X-Data, */
					/* or both in program memory */

					/* dstV returned */
					/* Only first N elements represent */
					/* DCT values scaled by 1/sqrt(2*N) */
);

/*...........................................................................*/

extern fractional* DCTIP (		/* Type II Discrete Cosine Transform */
					/* (in-place) */
   int log2N,				/* log2(N), N is transform length */
   fractional* srcV,			/* ptr to source vector in Y-Data */
   					/* MUST be zero padded to length 2*N */
					/* MUST be N modulo aligned */
   fractcomplex* cosFactors,		/* base address of cosine factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* CN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
					/* a total of N/2 complex values: */
					/* CN(k) = exp(i*k*pi/(2*N)) */
					/* CN(0)...CN(N/2-1) */
   fractcomplex* twidFactors,		/* base address of complex conjugate */
   					/* twiddle factors */
					/* either in X data or program memory */
					/* if in X data memory, it points at */
   					/* WN(0).real */
					/* if in program memory, base is the */
					/* offset from program page boundary */
					/* to address where factors located */
					/* (inline assembly psvoffset ()) */
					/* a total of N/2 complex values: */
					/* WN(k) = exp(-i*2*pi*k/N) */
					/* WN(0)...WN(N/2-1) */
   int factPage				/* if in X data memory, set to */
   					/* defined value COEFFS_IN_DATA */
					/* if in program memory, page number */
					/* where factors are located */
					/* (inline assembly psvpage ()) */

					/* Both, cosine and twiddle factors, */
					/* MUST be allocated in the same */
					/* memory space: both in X-Data, */
					/* or both in program memory */

					/* srcV returned */
					/* Only first N elements represent */
					/* DCT values scaled by 1/sqrt(2*N) */
);

/*...........................................................................*/

/***************************************************************************/

#endif	/* ] __DSP_LIB__ */

/***************************************************************************/
/* EOF */