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src/Cortex-M4-M3/FilteringFunctions/arm_biquad_cascade_df1_f32.c@0:1014af42efd9, 2011-03-10 (annotated)

Committer:: simon
Date:: Thu Mar 10 15:07:50 2011 +0000
Revision:: 0:1014af42efd9

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	0:1014af42efd9	1	/* ----------------------------------------------------------------------
simon	0:1014af42efd9	2	* Copyright (C) 2010 ARM Limited. All rights reserved.
simon	0:1014af42efd9	3	*
simon	0:1014af42efd9	4	* $Date: 29. November 2010
simon	0:1014af42efd9	5	* $Revision: V1.0.3
simon	0:1014af42efd9	6	*
simon	0:1014af42efd9	7	* Project: CMSIS DSP Library
simon	0:1014af42efd9	8	* Title: arm_biquad_cascade_df1_f32.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Processing function for the
simon	0:1014af42efd9	11	* floating-point Biquad cascade DirectFormI(DF1) filter.
simon	0:1014af42efd9	12	*
simon	0:1014af42efd9	13	* Target Processor: Cortex-M4/Cortex-M3
simon	0:1014af42efd9	14	*
simon	0:1014af42efd9	15	* Version 1.0.3 2010/11/29
simon	0:1014af42efd9	16	* Re-organized the CMSIS folders and updated documentation.
simon	0:1014af42efd9	17	*
simon	0:1014af42efd9	18	* Version 1.0.2 2010/11/11
simon	0:1014af42efd9	19	* Documentation updated.
simon	0:1014af42efd9	20	*
simon	0:1014af42efd9	21	* Version 1.0.1 2010/10/05
simon	0:1014af42efd9	22	* Production release and review comments incorporated.
simon	0:1014af42efd9	23	*
simon	0:1014af42efd9	24	* Version 1.0.0 2010/09/20
simon	0:1014af42efd9	25	* Production release and review comments incorporated.
simon	0:1014af42efd9	26	*
simon	0:1014af42efd9	27	* Version 0.0.5 2010/04/26
simon	0:1014af42efd9	28	* incorporated review comments and updated with latest CMSIS layer
simon	0:1014af42efd9	29	*
simon	0:1014af42efd9	30	* Version 0.0.3 2010/03/10
simon	0:1014af42efd9	31	* Initial version
simon	0:1014af42efd9	32	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	33
simon	0:1014af42efd9	34	#include "arm_math.h"
simon	0:1014af42efd9	35
simon	0:1014af42efd9	36	/**
simon	0:1014af42efd9	37	* @ingroup groupFilters
simon	0:1014af42efd9	38	*/
simon	0:1014af42efd9	39
simon	0:1014af42efd9	40	/**
simon	0:1014af42efd9	41	* @defgroup BiquadCascadeDF1 Biquad Cascade IIR Filters Using Direct Form I Structure
simon	0:1014af42efd9	42	*
simon	0:1014af42efd9	43	* This set of functions implements arbitrary order recursive (IIR) filters.
simon	0:1014af42efd9	44	* The filters are implemented as a cascade of second order Biquad sections.
simon	0:1014af42efd9	45	* The functions support Q15, Q31 and floating-point data types. Fast version of Q15 and Q31 also supported.
simon	0:1014af42efd9	46	*
simon	0:1014af42efd9	47	* The functions operate on blocks of input and output data and each call to the function
simon	0:1014af42efd9	48	* processes <code>blockSize</code> samples through the filter.
simon	0:1014af42efd9	49	* <code>pSrc</code> points to the array of input data and
simon	0:1014af42efd9	50	* <code>pDst</code> points to the array of output data.
simon	0:1014af42efd9	51	* Both arrays contain <code>blockSize</code> values.
simon	0:1014af42efd9	52	*
simon	0:1014af42efd9	53	* \par Algorithm
simon	0:1014af42efd9	54	* Each Biquad stage implements a second order filter using the difference equation:
simon	0:1014af42efd9	55	* <pre>
simon	0:1014af42efd9	56	* y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
simon	0:1014af42efd9	57	* </pre>
simon	0:1014af42efd9	58	* A Direct Form I algorithm is used with 5 coefficients and 4 state variables per stage.
simon	0:1014af42efd9	59	* \image html Biquad.gif "Single Biquad filter stage"
simon	0:1014af42efd9	60	* Coefficients <code>b0, b1 and b2 </code> multiply the input signal <code>x[n]</code> and are referred to as the feedforward coefficients.
simon	0:1014af42efd9	61	* Coefficients <code>a1</code> and <code>a2</code> multiply the output signal <code>y[n]</code> and are referred to as the feedback coefficients.
simon	0:1014af42efd9	62	* Pay careful attention to the sign of the feedback coefficients.
simon	0:1014af42efd9	63	* Some design tools use the difference equation
simon	0:1014af42efd9	64	* <pre>
simon	0:1014af42efd9	65	* y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] - a1 * y[n-1] - a2 * y[n-2]
simon	0:1014af42efd9	66	* </pre>
simon	0:1014af42efd9	67	* In this case the feedback coefficients <code>a1</code> and <code>a2</code> must be negated when used with the CMSIS DSP Library.
simon	0:1014af42efd9	68	*
simon	0:1014af42efd9	69	* \par
simon	0:1014af42efd9	70	* Higher order filters are realized as a cascade of second order sections.
simon	0:1014af42efd9	71	* <code>numStages</code> refers to the number of second order stages used.
simon	0:1014af42efd9	72	* For example, an 8th order filter would be realized with <code>numStages=4</code> second order stages.
simon	0:1014af42efd9	73	* \image html BiquadCascade.gif "8th order filter using a cascade of Biquad stages"
simon	0:1014af42efd9	74	* A 9th order filter would be realized with <code>numStages=5</code> second order stages with the coefficients for one of the stages configured as a first order filter (<code>b2=0</code> and <code>a2=0</code>).
simon	0:1014af42efd9	75	*
simon	0:1014af42efd9	76	* \par
simon	0:1014af42efd9	77	* The <code>pState</code> points to state variables array.
simon	0:1014af42efd9	78	* Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.
simon	0:1014af42efd9	79	* The state variables are arranged in the <code>pState</code> array as:
simon	0:1014af42efd9	80	* <pre>
simon	0:1014af42efd9	81	* {x[n-1], x[n-2], y[n-1], y[n-2]}
simon	0:1014af42efd9	82	* </pre>
simon	0:1014af42efd9	83	*
simon	0:1014af42efd9	84	* \par
simon	0:1014af42efd9	85	* The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
simon	0:1014af42efd9	86	* The state array has a total length of <code>4*numStages</code> values.
simon	0:1014af42efd9	87	* The state variables are updated after each block of data is processed, the coefficients are untouched.
simon	0:1014af42efd9	88	*
simon	0:1014af42efd9	89	* \par Instance Structure
simon	0:1014af42efd9	90	* The coefficients and state variables for a filter are stored together in an instance data structure.
simon	0:1014af42efd9	91	* A separate instance structure must be defined for each filter.
simon	0:1014af42efd9	92	* Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
simon	0:1014af42efd9	93	* There are separate instance structure declarations for each of the 3 supported data types.
simon	0:1014af42efd9	94	*
simon	0:1014af42efd9	95	* \par Init Functions
simon	0:1014af42efd9	96	* There is also an associated initialization function for each data type.
simon	0:1014af42efd9	97	* The initialization function performs following operations:
simon	0:1014af42efd9	98	* - Sets the values of the internal structure fields.
simon	0:1014af42efd9	99	* - Zeros out the values in the state buffer.
simon	0:1014af42efd9	100	*
simon	0:1014af42efd9	101	* \par
simon	0:1014af42efd9	102	* Use of the initialization function is optional.
simon	0:1014af42efd9	103	* However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
simon	0:1014af42efd9	104	* To place an instance structure into a const data section, the instance structure must be manually initialized.
simon	0:1014af42efd9	105	* Set the values in the state buffer to zeros before static initialization.
simon	0:1014af42efd9	106	* The code below statically initializes each of the 3 different data type filter instance structures
simon	0:1014af42efd9	107	* <pre>
simon	0:1014af42efd9	108	* arm_biquad_casd_df1_inst_f32 S1 = {numStages, pState, pCoeffs};
simon	0:1014af42efd9	109	* arm_biquad_casd_df1_inst_q15 S2 = {numStages, pState, pCoeffs, postShift};
simon	0:1014af42efd9	110	* arm_biquad_casd_df1_inst_q31 S3 = {numStages, pState, pCoeffs, postShift};
simon	0:1014af42efd9	111	* </pre>
simon	0:1014af42efd9	112	* where <code>numStages</code> is the number of Biquad stages in the filter; <code>pState</code> is the address of the state buffer;
simon	0:1014af42efd9	113	* <code>pCoeffs</code> is the address of the coefficient buffer; <code>postShift</code> shift to be applied.
simon	0:1014af42efd9	114	*
simon	0:1014af42efd9	115	* \par Fixed-Point Behavior
simon	0:1014af42efd9	116	* Care must be taken when using the Q15 and Q31 versions of the Biquad Cascade filter functions.
simon	0:1014af42efd9	117	* Following issues must be considered:
simon	0:1014af42efd9	118	* - Scaling of coefficients
simon	0:1014af42efd9	119	* - Filter gain
simon	0:1014af42efd9	120	* - Overflow and saturation
simon	0:1014af42efd9	121	*
simon	0:1014af42efd9	122	* \par
simon	0:1014af42efd9	123	* <b>Scaling of coefficients: </b>
simon	0:1014af42efd9	124	* Filter coefficients are represented as fractional values and
simon	0:1014af42efd9	125	* coefficients are restricted to lie in the range <code>[-1 +1)</code>.
simon	0:1014af42efd9	126	* The fixed-point functions have an additional scaling parameter <code>postShift</code>
simon	0:1014af42efd9	127	* which allow the filter coefficients to exceed the range <code>[+1 -1)</code>.
simon	0:1014af42efd9	128	* At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits.
simon	0:1014af42efd9	129	* \image html BiquadPostshift.gif "Fixed-point Biquad with shift by postShift bits after accumulator"
simon	0:1014af42efd9	130	* This essentially scales the filter coefficients by <code>2^postShift</code>.
simon	0:1014af42efd9	131	* For example, to realize the coefficients
simon	0:1014af42efd9	132	* <pre>
simon	0:1014af42efd9	133	* {1.5, -0.8, 1.2, 1.6, -0.9}
simon	0:1014af42efd9	134	* </pre>
simon	0:1014af42efd9	135	* set the pCoeffs array to:
simon	0:1014af42efd9	136	* <pre>
simon	0:1014af42efd9	137	* {0.75, -0.4, 0.6, 0.8, -0.45}
simon	0:1014af42efd9	138	* </pre>
simon	0:1014af42efd9	139	* and set <code>postShift=1</code>
simon	0:1014af42efd9	140	*
simon	0:1014af42efd9	141	* \par
simon	0:1014af42efd9	142	* <b>Filter gain: </b>
simon	0:1014af42efd9	143	* The frequency response of a Biquad filter is a function of its coefficients.
simon	0:1014af42efd9	144	* It is possible for the gain through the filter to exceed 1.0 meaning that the filter increases the amplitude of certain frequencies.
simon	0:1014af42efd9	145	* This means that an input signal with amplitude < 1.0 may result in an output > 1.0 and these are saturated or overflowed based on the implementation of the filter.
simon	0:1014af42efd9	146	* To avoid this behavior the filter needs to be scaled down such that its peak gain < 1.0 or the input signal must be scaled down so that the combination of input and filter are never overflowed.
simon	0:1014af42efd9	147	*
simon	0:1014af42efd9	148	* \par
simon	0:1014af42efd9	149	* <b>Overflow and saturation: </b>
simon	0:1014af42efd9	150	* For Q15 and Q31 versions, it is described separately as part of the function specific documentation below.
simon	0:1014af42efd9	151	*/
simon	0:1014af42efd9	152
simon	0:1014af42efd9	153	/**
simon	0:1014af42efd9	154	* @addtogroup BiquadCascadeDF1
simon	0:1014af42efd9	155	* @{
simon	0:1014af42efd9	156	*/
simon	0:1014af42efd9	157
simon	0:1014af42efd9	158	/**
simon	0:1014af42efd9	159	* @param[in] *S points to an instance of the floating-point Biquad cascade structure.
simon	0:1014af42efd9	160	* @param[in] *pSrc points to the block of input data.
simon	0:1014af42efd9	161	* @param[out] *pDst points to the block of output data.
simon	0:1014af42efd9	162	* @param[in] blockSize number of samples to process per call.
simon	0:1014af42efd9	163	* @return none.
simon	0:1014af42efd9	164	*
simon	0:1014af42efd9	165	*/
simon	0:1014af42efd9	166
simon	0:1014af42efd9	167	void arm_biquad_cascade_df1_f32(
simon	0:1014af42efd9	168	const arm_biquad_casd_df1_inst_f32 * S,
simon	0:1014af42efd9	169	float32_t * pSrc,
simon	0:1014af42efd9	170	float32_t * pDst,
simon	0:1014af42efd9	171	uint32_t blockSize)
simon	0:1014af42efd9	172	{
simon	0:1014af42efd9	173	float32_t pIn = pSrc; / source pointer */
simon	0:1014af42efd9	174	float32_t pOut = pDst; / destination pointer */
simon	0:1014af42efd9	175	float32_t pState = S->pState; / pState pointer */
simon	0:1014af42efd9	176	float32_t pCoeffs = S->pCoeffs; / coefficient pointer */
simon	0:1014af42efd9	177	float32_t acc; /* Simulates the accumulator */
simon	0:1014af42efd9	178	float32_t b0, b1, b2, a1, a2; /* Filter coefficients */
simon	0:1014af42efd9	179	float32_t Xn1, Xn2, Yn1, Yn2; /* Filter pState variables */
simon	0:1014af42efd9	180	float32_t Xn; /* temporary input */
simon	0:1014af42efd9	181	uint32_t sample, stage = S->numStages; /* loop counters */
simon	0:1014af42efd9	182
simon	0:1014af42efd9	183
simon	0:1014af42efd9	184	do
simon	0:1014af42efd9	185	{
simon	0:1014af42efd9	186	/* Reading the coefficients */
simon	0:1014af42efd9	187	b0 = *pCoeffs++;
simon	0:1014af42efd9	188	b1 = *pCoeffs++;
simon	0:1014af42efd9	189	b2 = *pCoeffs++;
simon	0:1014af42efd9	190	a1 = *pCoeffs++;
simon	0:1014af42efd9	191	a2 = *pCoeffs++;
simon	0:1014af42efd9	192
simon	0:1014af42efd9	193	/* Reading the pState values */
simon	0:1014af42efd9	194	Xn1 = pState[0];
simon	0:1014af42efd9	195	Xn2 = pState[1];
simon	0:1014af42efd9	196	Yn1 = pState[2];
simon	0:1014af42efd9	197	Yn2 = pState[3];
simon	0:1014af42efd9	198
simon	0:1014af42efd9	199	/* Apply loop unrolling and compute 4 output values simultaneously. */
simon	0:1014af42efd9	200	/* The variable acc hold output values that are being computed:
simon	0:1014af42efd9	201	*
simon	0:1014af42efd9	202	* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
simon	0:1014af42efd9	203	* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
simon	0:1014af42efd9	204	* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
simon	0:1014af42efd9	205	* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
simon	0:1014af42efd9	206	*/
simon	0:1014af42efd9	207
simon	0:1014af42efd9	208	sample = blockSize >> 2u;
simon	0:1014af42efd9	209
simon	0:1014af42efd9	210	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	211	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	212	while(sample > 0u)
simon	0:1014af42efd9	213	{
simon	0:1014af42efd9	214	/* Read the first input */
simon	0:1014af42efd9	215	Xn = *pIn++;
simon	0:1014af42efd9	216
simon	0:1014af42efd9	217	/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
simon	0:1014af42efd9	218	Yn2 = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2);
simon	0:1014af42efd9	219
simon	0:1014af42efd9	220	/* Store the result in the accumulator in the destination buffer. */
simon	0:1014af42efd9	221	*pOut++ = Yn2;
simon	0:1014af42efd9	222
simon	0:1014af42efd9	223	/* Every time after the output is computed state should be updated. */
simon	0:1014af42efd9	224	/* The states should be updated as: */
simon	0:1014af42efd9	225	/* Xn2 = Xn1 */
simon	0:1014af42efd9	226	/* Xn1 = Xn */
simon	0:1014af42efd9	227	/* Yn2 = Yn1 */
simon	0:1014af42efd9	228	/* Yn1 = acc */
simon	0:1014af42efd9	229
simon	0:1014af42efd9	230	/* Read the second input */
simon	0:1014af42efd9	231	Xn2 = *pIn++;
simon	0:1014af42efd9	232
simon	0:1014af42efd9	233	/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
simon	0:1014af42efd9	234	Yn1 = (b0 * Xn2) + (b1 * Xn) + (b2 * Xn1) + (a1 * Yn2) + (a2 * Yn1);
simon	0:1014af42efd9	235
simon	0:1014af42efd9	236	/* Store the result in the accumulator in the destination buffer. */
simon	0:1014af42efd9	237	*pOut++ = Yn1;
simon	0:1014af42efd9	238
simon	0:1014af42efd9	239	/* Every time after the output is computed state should be updated. */
simon	0:1014af42efd9	240	/* The states should be updated as: */
simon	0:1014af42efd9	241	/* Xn2 = Xn1 */
simon	0:1014af42efd9	242	/* Xn1 = Xn */
simon	0:1014af42efd9	243	/* Yn2 = Yn1 */
simon	0:1014af42efd9	244	/* Yn1 = acc */
simon	0:1014af42efd9	245
simon	0:1014af42efd9	246	/* Read the third input */
simon	0:1014af42efd9	247	Xn1 = *pIn++;
simon	0:1014af42efd9	248
simon	0:1014af42efd9	249	/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
simon	0:1014af42efd9	250	Yn2 = (b0 * Xn1) + (b1 * Xn2) + (b2 * Xn) + (a1 * Yn1) + (a2 * Yn2);
simon	0:1014af42efd9	251
simon	0:1014af42efd9	252	/* Store the result in the accumulator in the destination buffer. */
simon	0:1014af42efd9	253	*pOut++ = Yn2;
simon	0:1014af42efd9	254
simon	0:1014af42efd9	255	/* Every time after the output is computed state should be updated. */
simon	0:1014af42efd9	256	/* The states should be updated as: */
simon	0:1014af42efd9	257	/* Xn2 = Xn1 */
simon	0:1014af42efd9	258	/* Xn1 = Xn */
simon	0:1014af42efd9	259	/* Yn2 = Yn1 */
simon	0:1014af42efd9	260	/* Yn1 = acc */
simon	0:1014af42efd9	261
simon	0:1014af42efd9	262	/* Read the forth input */
simon	0:1014af42efd9	263	Xn = *pIn++;
simon	0:1014af42efd9	264
simon	0:1014af42efd9	265	/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
simon	0:1014af42efd9	266	Yn1 = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn2) + (a2 * Yn1);
simon	0:1014af42efd9	267
simon	0:1014af42efd9	268	/* Store the result in the accumulator in the destination buffer. */
simon	0:1014af42efd9	269	*pOut++ = Yn1;
simon	0:1014af42efd9	270
simon	0:1014af42efd9	271	/* Every time after the output is computed state should be updated. */
simon	0:1014af42efd9	272	/* The states should be updated as: */
simon	0:1014af42efd9	273	/* Xn2 = Xn1 */
simon	0:1014af42efd9	274	/* Xn1 = Xn */
simon	0:1014af42efd9	275	/* Yn2 = Yn1 */
simon	0:1014af42efd9	276	/* Yn1 = acc */
simon	0:1014af42efd9	277	Xn2 = Xn1;
simon	0:1014af42efd9	278	Xn1 = Xn;
simon	0:1014af42efd9	279
simon	0:1014af42efd9	280	/* decrement the loop counter */
simon	0:1014af42efd9	281	sample--;
simon	0:1014af42efd9	282
simon	0:1014af42efd9	283	}
simon	0:1014af42efd9	284
simon	0:1014af42efd9	285	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	286	** No loop unrolling is used. */
simon	0:1014af42efd9	287	sample = blockSize & 0x3u;
simon	0:1014af42efd9	288
simon	0:1014af42efd9	289	while(sample > 0u)
simon	0:1014af42efd9	290	{
simon	0:1014af42efd9	291	/* Read the input */
simon	0:1014af42efd9	292	Xn = *pIn++;
simon	0:1014af42efd9	293
simon	0:1014af42efd9	294	/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
simon	0:1014af42efd9	295	acc = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2);
simon	0:1014af42efd9	296
simon	0:1014af42efd9	297	/* Store the result in the accumulator in the destination buffer. */
simon	0:1014af42efd9	298	*pOut++ = acc;
simon	0:1014af42efd9	299
simon	0:1014af42efd9	300	/* Every time after the output is computed state should be updated. */
simon	0:1014af42efd9	301	/* The states should be updated as: */
simon	0:1014af42efd9	302	/* Xn2 = Xn1 */
simon	0:1014af42efd9	303	/* Xn1 = Xn */
simon	0:1014af42efd9	304	/* Yn2 = Yn1 */
simon	0:1014af42efd9	305	/* Yn1 = acc */
simon	0:1014af42efd9	306	Xn2 = Xn1;
simon	0:1014af42efd9	307	Xn1 = Xn;
simon	0:1014af42efd9	308	Yn2 = Yn1;
simon	0:1014af42efd9	309	Yn1 = acc;
simon	0:1014af42efd9	310
simon	0:1014af42efd9	311	/* decrement the loop counter */
simon	0:1014af42efd9	312	sample--;
simon	0:1014af42efd9	313
simon	0:1014af42efd9	314	}
simon	0:1014af42efd9	315
simon	0:1014af42efd9	316	/* Store the updated state variables back into the pState array */
simon	0:1014af42efd9	317	*pState++ = Xn1;
simon	0:1014af42efd9	318	*pState++ = Xn2;
simon	0:1014af42efd9	319	*pState++ = Yn1;
simon	0:1014af42efd9	320	*pState++ = Yn2;
simon	0:1014af42efd9	321
simon	0:1014af42efd9	322	/* The first stage goes from the input wire to the output wire. */
simon	0:1014af42efd9	323	/* Subsequent numStages occur in-place in the output wire */
simon	0:1014af42efd9	324	pIn = pDst;
simon	0:1014af42efd9	325
simon	0:1014af42efd9	326	/* Reset the output pointer */
simon	0:1014af42efd9	327	pOut = pDst;
simon	0:1014af42efd9	328
simon	0:1014af42efd9	329	/* decrement the loop counter */
simon	0:1014af42efd9	330	stage--;
simon	0:1014af42efd9	331
simon	0:1014af42efd9	332	} while(stage > 0u);
simon	0:1014af42efd9	333
simon	0:1014af42efd9	334	}
simon	0:1014af42efd9	335
simon	0:1014af42efd9	336
simon	0:1014af42efd9	337	/**
simon	0:1014af42efd9	338	* @} end of BiquadCascadeDF1 group
simon	0:1014af42efd9	339	*/

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Type:	Library
Created:	10 Mar 2011
Imports:	907
Forks:	1
Commits:	3
Dependents:	5
Dependencies:	0
Followers:	35

src/Cortex-M4-M3/FilteringFunctions/arm_biquad_cascade_df1_f32.c@0:1014af42efd9, 2011-03-10 (annotated)

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