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src/Cortex-M4-M3/FilteringFunctions/arm_fir_lattice_q31.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_fir_lattice_q31.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Q31 FIR lattice filter processing function.
simon	0:1014af42efd9	11	*
simon	0:1014af42efd9	12	* Target Processor: Cortex-M4/Cortex-M3
simon	0:1014af42efd9	13	*
simon	0:1014af42efd9	14	* Version 1.0.3 2010/11/29
simon	0:1014af42efd9	15	* Re-organized the CMSIS folders and updated documentation.
simon	0:1014af42efd9	16	*
simon	0:1014af42efd9	17	* Version 1.0.2 2010/11/11
simon	0:1014af42efd9	18	* Documentation updated.
simon	0:1014af42efd9	19	*
simon	0:1014af42efd9	20	* Version 1.0.1 2010/10/05
simon	0:1014af42efd9	21	* Production release and review comments incorporated.
simon	0:1014af42efd9	22	*
simon	0:1014af42efd9	23	* Version 1.0.0 2010/09/20
simon	0:1014af42efd9	24	* Production release and review comments incorporated
simon	0:1014af42efd9	25	*
simon	0:1014af42efd9	26	* Version 0.0.7 2010/06/10
simon	0:1014af42efd9	27	* Misra-C changes done
simon	0:1014af42efd9	28	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	29
simon	0:1014af42efd9	30	#include "arm_math.h"
simon	0:1014af42efd9	31
simon	0:1014af42efd9	32	/**
simon	0:1014af42efd9	33	* @ingroup groupFilters
simon	0:1014af42efd9	34	*/
simon	0:1014af42efd9	35
simon	0:1014af42efd9	36	/**
simon	0:1014af42efd9	37	* @addtogroup FIR_Lattice
simon	0:1014af42efd9	38	* @{
simon	0:1014af42efd9	39	*/
simon	0:1014af42efd9	40
simon	0:1014af42efd9	41
simon	0:1014af42efd9	42	/**
simon	0:1014af42efd9	43	* @brief Processing function for the Q31 FIR lattice filter.
simon	0:1014af42efd9	44	* @param[in] *S points to an instance of the Q31 FIR lattice structure.
simon	0:1014af42efd9	45	* @param[in] *pSrc points to the block of input data.
simon	0:1014af42efd9	46	* @param[out] *pDst points to the block of output data
simon	0:1014af42efd9	47	* @param[in] blockSize number of samples to process.
simon	0:1014af42efd9	48	* @return none.
simon	0:1014af42efd9	49	*
simon	0:1014af42efd9	50	* @details
simon	0:1014af42efd9	51	* <b>Scaling and Overflow Behavior:</b>
simon	0:1014af42efd9	52	* In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits.
simon	0:1014af42efd9	53	*/
simon	0:1014af42efd9	54
simon	0:1014af42efd9	55	void arm_fir_lattice_q31(
simon	0:1014af42efd9	56	const arm_fir_lattice_instance_q31 * S,
simon	0:1014af42efd9	57	q31_t * pSrc,
simon	0:1014af42efd9	58	q31_t * pDst,
simon	0:1014af42efd9	59	uint32_t blockSize)
simon	0:1014af42efd9	60	{
simon	0:1014af42efd9	61	q31_t pState; / State pointer */
simon	0:1014af42efd9	62	q31_t pCoeffs = S->pCoeffs; / Coefficient pointer */
simon	0:1014af42efd9	63	q31_t px; / temporary state pointer */
simon	0:1014af42efd9	64	q31_t pk; / temporary coefficient pointer */
simon	0:1014af42efd9	65	q31_t fcurr1, fnext1, gcurr1 = 0, gnext1; /* temporary variables for first sample in loop unrolling */
simon	0:1014af42efd9	66	q63_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */
simon	0:1014af42efd9	67	q63_t fcurr3, fnext3, gnext3; /* temporary variables for third sample in loop unrolling */
simon	0:1014af42efd9	68	q63_t fcurr4, fnext4, gnext4; /* temporary variables for fourth sample in loop unrolling */
simon	0:1014af42efd9	69	uint32_t numStages = S->numStages; /* Length of the filter */
simon	0:1014af42efd9	70	uint32_t blkCnt, stageCnt; /* temporary variables for counts */
simon	0:1014af42efd9	71
simon	0:1014af42efd9	72	pState = &S->pState[0];
simon	0:1014af42efd9	73
simon	0:1014af42efd9	74	blkCnt = blockSize >> 2u;
simon	0:1014af42efd9	75
simon	0:1014af42efd9	76	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	77	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	78	while(blkCnt > 0u)
simon	0:1014af42efd9	79	{
simon	0:1014af42efd9	80
simon	0:1014af42efd9	81	/* Read two samples from input buffer */
simon	0:1014af42efd9	82	/* f0(n) = x(n) */
simon	0:1014af42efd9	83	fcurr1 = *pSrc++;
simon	0:1014af42efd9	84	/* f0(n) = x(n) */
simon	0:1014af42efd9	85	fcurr2 = *pSrc++;
simon	0:1014af42efd9	86
simon	0:1014af42efd9	87	/* Initialize coeff pointer */
simon	0:1014af42efd9	88	pk = (pCoeffs);
simon	0:1014af42efd9	89
simon	0:1014af42efd9	90	/* Initialize state pointer */
simon	0:1014af42efd9	91	px = pState;
simon	0:1014af42efd9	92
simon	0:1014af42efd9	93	/* Read g0(n-1) from state */
simon	0:1014af42efd9	94	gcurr1 = *px;
simon	0:1014af42efd9	95
simon	0:1014af42efd9	96	/* Process first sample for first tap */
simon	0:1014af42efd9	97	/* f1(n) = f0(n) + K1 * g0(n-1) */
simon	0:1014af42efd9	98	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	99	/* g1(n) = f0(n) * K1 + g0(n-1) */
simon	0:1014af42efd9	100	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk)) >> 31) + gcurr1;
simon	0:1014af42efd9	101
simon	0:1014af42efd9	102	/* Process second sample for first tap */
simon	0:1014af42efd9	103	/* for sample 2 processing */
simon	0:1014af42efd9	104	fnext2 = (q31_t) (((q63_t) fcurr1 * (*pk)) >> 31) + fcurr2;
simon	0:1014af42efd9	105	gnext2 = (q31_t) (((q63_t) fcurr2 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	106
simon	0:1014af42efd9	107
simon	0:1014af42efd9	108	/* Read next two samples from input buffer */
simon	0:1014af42efd9	109	/* f0(n+2) = x(n+2) */
simon	0:1014af42efd9	110	fcurr3 = *pSrc++;
simon	0:1014af42efd9	111	fcurr4 = *pSrc++;
simon	0:1014af42efd9	112
simon	0:1014af42efd9	113	/* Copy only last input samples into the state buffer
simon	0:1014af42efd9	114	which will be used for next four samples processing */
simon	0:1014af42efd9	115	*px++ = (q31_t) fcurr4;
simon	0:1014af42efd9	116
simon	0:1014af42efd9	117	/* Process third sample for first tap */
simon	0:1014af42efd9	118	fnext3 = (q31_t) (((q63_t) fcurr2 * (*pk)) >> 31) + fcurr3;
simon	0:1014af42efd9	119	gnext3 = (q31_t) (((q63_t) fcurr3 * (*pk)) >> 31) + fcurr2;
simon	0:1014af42efd9	120
simon	0:1014af42efd9	121	/* Process fourth sample for first tap */
simon	0:1014af42efd9	122	fnext4 = (q31_t) (((q63_t) fcurr3 * (*pk)) >> 31) + fcurr4;
simon	0:1014af42efd9	123	gnext4 = (q31_t) (((q63_t) fcurr4 * (*pk++)) >> 31) + fcurr3;
simon	0:1014af42efd9	124
simon	0:1014af42efd9	125	/* save g1(n) in state buffer for next sample processing */
simon	0:1014af42efd9	126	/* px++ = gnext4; /
simon	0:1014af42efd9	127
simon	0:1014af42efd9	128	/* Update of f values for next coefficient set processing */
simon	0:1014af42efd9	129	fcurr1 = fnext1;
simon	0:1014af42efd9	130	fcurr2 = fnext2;
simon	0:1014af42efd9	131	fcurr3 = fnext3;
simon	0:1014af42efd9	132	fcurr4 = fnext4;
simon	0:1014af42efd9	133
simon	0:1014af42efd9	134
simon	0:1014af42efd9	135	/* Loop unrolling. Process 4 taps at a time . */
simon	0:1014af42efd9	136	stageCnt = (numStages - 1u) >> 2u;
simon	0:1014af42efd9	137
simon	0:1014af42efd9	138
simon	0:1014af42efd9	139	/* Loop over the number of taps. Unroll by a factor of 4.
simon	0:1014af42efd9	140	** Repeat until we've computed numStages-3 coefficients. */
simon	0:1014af42efd9	141
simon	0:1014af42efd9	142	/* Process 2nd, 3rd, 4th and 5th taps ... here */
simon	0:1014af42efd9	143	while(stageCnt > 0u)
simon	0:1014af42efd9	144	{
simon	0:1014af42efd9	145	/* Read g1(n-1), g3(n-1) .... from state */
simon	0:1014af42efd9	146	gcurr1 = *px;
simon	0:1014af42efd9	147
simon	0:1014af42efd9	148	/* save g1(n) in state buffer */
simon	0:1014af42efd9	149	*px++ = (q31_t) gnext4;
simon	0:1014af42efd9	150
simon	0:1014af42efd9	151	/* Process first sample for 2nd, 6th .. tap */
simon	0:1014af42efd9	152	/* Sample processing for K2, K6.... */
simon	0:1014af42efd9	153	/* f2(n) = f1(n) + K2 * g1(n-1) */
simon	0:1014af42efd9	154	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	155	/* Process second sample for 2nd, 6th .. tap */
simon	0:1014af42efd9	156	/* for sample 2 processing */
simon	0:1014af42efd9	157	fnext2 = (q31_t) (((q63_t) gnext1 * (*pk)) >> 31) + fcurr2;
simon	0:1014af42efd9	158	/* Process third sample for 2nd, 6th .. tap */
simon	0:1014af42efd9	159	fnext3 = (q31_t) (((q63_t) gnext2 * (*pk)) >> 31) + fcurr3;
simon	0:1014af42efd9	160	/* Process fourth sample for 2nd, 6th .. tap */
simon	0:1014af42efd9	161	fnext4 = (q31_t) (((q63_t) gnext3 * (*pk)) >> 31) + fcurr4;
simon	0:1014af42efd9	162
simon	0:1014af42efd9	163	/* g2(n) = f1(n) * K2 + g1(n-1) */
simon	0:1014af42efd9	164	/* Calculation of state values for next stage */
simon	0:1014af42efd9	165	gnext4 = (q31_t) (((q63_t) fcurr4 * (*pk)) >> 31) + gnext3;
simon	0:1014af42efd9	166	gnext3 = (q31_t) (((q63_t) fcurr3 * (*pk)) >> 31) + gnext2;
simon	0:1014af42efd9	167	gnext2 = (q31_t) (((q63_t) fcurr2 * (*pk)) >> 31) + gnext1;
simon	0:1014af42efd9	168	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	169
simon	0:1014af42efd9	170
simon	0:1014af42efd9	171	/* Read g2(n-1), g4(n-1) .... from state */
simon	0:1014af42efd9	172	gcurr1 = *px;
simon	0:1014af42efd9	173
simon	0:1014af42efd9	174	/* save g2(n) in state buffer */
simon	0:1014af42efd9	175	*px++ = (q31_t) gnext4;
simon	0:1014af42efd9	176
simon	0:1014af42efd9	177	/* Sample processing for K3, K7.... */
simon	0:1014af42efd9	178	/* Process first sample for 3rd, 7th .. tap */
simon	0:1014af42efd9	179	/* f3(n) = f2(n) + K3 * g2(n-1) */
simon	0:1014af42efd9	180	fcurr1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fnext1;
simon	0:1014af42efd9	181	/* Process second sample for 3rd, 7th .. tap */
simon	0:1014af42efd9	182	fcurr2 = (q31_t) (((q63_t) gnext1 * (*pk)) >> 31) + fnext2;
simon	0:1014af42efd9	183	/* Process third sample for 3rd, 7th .. tap */
simon	0:1014af42efd9	184	fcurr3 = (q31_t) (((q63_t) gnext2 * (*pk)) >> 31) + fnext3;
simon	0:1014af42efd9	185	/* Process fourth sample for 3rd, 7th .. tap */
simon	0:1014af42efd9	186	fcurr4 = (q31_t) (((q63_t) gnext3 * (*pk)) >> 31) + fnext4;
simon	0:1014af42efd9	187
simon	0:1014af42efd9	188	/* Calculation of state values for next stage */
simon	0:1014af42efd9	189	/* gnext4 = fnext4 * (pk) + gnext3; /
simon	0:1014af42efd9	190	gnext4 = (q31_t) (((q63_t) fnext4 * (*pk)) >> 31) + gnext3;
simon	0:1014af42efd9	191	gnext3 = (q31_t) (((q63_t) fnext3 * (*pk)) >> 31) + gnext2;
simon	0:1014af42efd9	192	/* gnext2 = fnext2 * (pk) + gnext1; /
simon	0:1014af42efd9	193	gnext2 = (q31_t) (((q63_t) fnext2 * (*pk)) >> 31) + gnext1;
simon	0:1014af42efd9	194
simon	0:1014af42efd9	195	/* g1(n) = f0(n) * K1 + g0(n-1) */
simon	0:1014af42efd9	196	/* gnext1 = fnext1 * (pk++) + gcurr1; /
simon	0:1014af42efd9	197	gnext1 = (q31_t) (((q63_t) fnext1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	198
simon	0:1014af42efd9	199	/* Read g1(n-1), g3(n-1) .... from state */
simon	0:1014af42efd9	200	gcurr1 = *px;
simon	0:1014af42efd9	201
simon	0:1014af42efd9	202	/* save g1(n) in state buffer */
simon	0:1014af42efd9	203	*px++ = (q31_t) gnext4;
simon	0:1014af42efd9	204
simon	0:1014af42efd9	205	/* Sample processing for K4, K8.... */
simon	0:1014af42efd9	206	/* Process first sample for 4th, 8th .. tap */
simon	0:1014af42efd9	207	/* f4(n) = f3(n) + K4 * g3(n-1) */
simon	0:1014af42efd9	208	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	209	/* Process second sample for 4th, 8th .. tap */
simon	0:1014af42efd9	210	/* for sample 2 processing */
simon	0:1014af42efd9	211	fnext2 = (q31_t) (((q63_t) gnext1 * (*pk)) >> 31) + fcurr2;
simon	0:1014af42efd9	212	/* Process third sample for 4th, 8th .. tap */
simon	0:1014af42efd9	213	fnext3 = (q31_t) (((q63_t) gnext2 * (*pk)) >> 31) + fcurr3;
simon	0:1014af42efd9	214	/* Process fourth sample for 4th, 8th .. tap */
simon	0:1014af42efd9	215	fnext4 = (q31_t) (((q63_t) gnext3 * (*pk)) >> 31) + fcurr4;
simon	0:1014af42efd9	216
simon	0:1014af42efd9	217	/* g4(n) = f3(n) * K4 + g3(n-1) */
simon	0:1014af42efd9	218	/* Calculation of state values for next stage */
simon	0:1014af42efd9	219	gnext4 = (q31_t) (((q63_t) fcurr4 * (*pk)) >> 31) + gnext3;
simon	0:1014af42efd9	220	gnext3 = (q31_t) (((q63_t) fcurr3 * (*pk)) >> 31) + gnext2;
simon	0:1014af42efd9	221	gnext2 = (q31_t) (((q63_t) fcurr2 * (*pk)) >> 31) + gnext1;
simon	0:1014af42efd9	222	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	223
simon	0:1014af42efd9	224	/* Read g2(n-1), g4(n-1) .... from state */
simon	0:1014af42efd9	225	gcurr1 = *px;
simon	0:1014af42efd9	226
simon	0:1014af42efd9	227	/* save g4(n) in state buffer */
simon	0:1014af42efd9	228	*px++ = (q31_t) gnext4;
simon	0:1014af42efd9	229
simon	0:1014af42efd9	230	/* Sample processing for K5, K9.... */
simon	0:1014af42efd9	231	/* Process first sample for 5th, 9th .. tap */
simon	0:1014af42efd9	232	/* f5(n) = f4(n) + K5 * g4(n-1) */
simon	0:1014af42efd9	233	fcurr1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fnext1;
simon	0:1014af42efd9	234	/* Process second sample for 5th, 9th .. tap */
simon	0:1014af42efd9	235	fcurr2 = (q31_t) (((q63_t) gnext1 * (*pk)) >> 31) + fnext2;
simon	0:1014af42efd9	236	/* Process third sample for 5th, 9th .. tap */
simon	0:1014af42efd9	237	fcurr3 = (q31_t) (((q63_t) gnext2 * (*pk)) >> 31) + fnext3;
simon	0:1014af42efd9	238	/* Process fourth sample for 5th, 9th .. tap */
simon	0:1014af42efd9	239	fcurr4 = (q31_t) (((q63_t) gnext3 * (*pk)) >> 31) + fnext4;
simon	0:1014af42efd9	240
simon	0:1014af42efd9	241	/* Calculation of state values for next stage */
simon	0:1014af42efd9	242	/* g5(n) = f4(n) * K5 + g4(n-1) */
simon	0:1014af42efd9	243	gnext4 = (q31_t) (((q63_t) fnext4 * (*pk)) >> 31) + gnext3;
simon	0:1014af42efd9	244	gnext3 = (q31_t) (((q63_t) fnext3 * (*pk)) >> 31) + gnext2;
simon	0:1014af42efd9	245	gnext2 = (q31_t) (((q63_t) fnext2 * (*pk)) >> 31) + gnext1;
simon	0:1014af42efd9	246	gnext1 = (q31_t) (((q63_t) fnext1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	247
simon	0:1014af42efd9	248	stageCnt--;
simon	0:1014af42efd9	249	}
simon	0:1014af42efd9	250
simon	0:1014af42efd9	251	/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
simon	0:1014af42efd9	252	stageCnt = (numStages - 1u) % 0x4u;
simon	0:1014af42efd9	253
simon	0:1014af42efd9	254	while(stageCnt > 0u)
simon	0:1014af42efd9	255	{
simon	0:1014af42efd9	256	gcurr1 = *px;
simon	0:1014af42efd9	257
simon	0:1014af42efd9	258	/* save g value in state buffer */
simon	0:1014af42efd9	259	*px++ = (q31_t) gnext4;
simon	0:1014af42efd9	260
simon	0:1014af42efd9	261	/* Process four samples for last three taps here */
simon	0:1014af42efd9	262	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	263	fnext2 = (q31_t) (((q63_t) gnext1 * (*pk)) >> 31) + fcurr2;
simon	0:1014af42efd9	264	fnext3 = (q31_t) (((q63_t) gnext2 * (*pk)) >> 31) + fcurr3;
simon	0:1014af42efd9	265	fnext4 = (q31_t) (((q63_t) gnext3 * (*pk)) >> 31) + fcurr4;
simon	0:1014af42efd9	266
simon	0:1014af42efd9	267	/* g1(n) = f0(n) * K1 + g0(n-1) */
simon	0:1014af42efd9	268	gnext4 = (q31_t) (((q63_t) fcurr4 * (*pk)) >> 31) + gnext3;
simon	0:1014af42efd9	269	gnext3 = (q31_t) (((q63_t) fcurr3 * (*pk)) >> 31) + gnext2;
simon	0:1014af42efd9	270	gnext2 = (q31_t) (((q63_t) fcurr2 * (*pk)) >> 31) + gnext1;
simon	0:1014af42efd9	271	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	272
simon	0:1014af42efd9	273	/* Update of f values for next coefficient set processing */
simon	0:1014af42efd9	274	fcurr1 = fnext1;
simon	0:1014af42efd9	275	fcurr2 = fnext2;
simon	0:1014af42efd9	276	fcurr3 = fnext3;
simon	0:1014af42efd9	277	fcurr4 = fnext4;
simon	0:1014af42efd9	278
simon	0:1014af42efd9	279	stageCnt--;
simon	0:1014af42efd9	280
simon	0:1014af42efd9	281	}
simon	0:1014af42efd9	282
simon	0:1014af42efd9	283	/* The results in the 4 accumulators, store in the destination buffer. */
simon	0:1014af42efd9	284	/* y(n) = fN(n) */
simon	0:1014af42efd9	285	*pDst++ = fcurr1;
simon	0:1014af42efd9	286	*pDst++ = (q31_t) fcurr2;
simon	0:1014af42efd9	287	*pDst++ = (q31_t) fcurr3;
simon	0:1014af42efd9	288	*pDst++ = (q31_t) fcurr4;
simon	0:1014af42efd9	289
simon	0:1014af42efd9	290	blkCnt--;
simon	0:1014af42efd9	291	}
simon	0:1014af42efd9	292
simon	0:1014af42efd9	293	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	294	** No loop unrolling is used. */
simon	0:1014af42efd9	295	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	296
simon	0:1014af42efd9	297	while(blkCnt > 0u)
simon	0:1014af42efd9	298	{
simon	0:1014af42efd9	299	/* f0(n) = x(n) */
simon	0:1014af42efd9	300	fcurr1 = *pSrc++;
simon	0:1014af42efd9	301
simon	0:1014af42efd9	302	/* Initialize coeff pointer */
simon	0:1014af42efd9	303	pk = (pCoeffs);
simon	0:1014af42efd9	304
simon	0:1014af42efd9	305	/* Initialize state pointer */
simon	0:1014af42efd9	306	px = pState;
simon	0:1014af42efd9	307
simon	0:1014af42efd9	308	/* read g2(n) from state buffer */
simon	0:1014af42efd9	309	gcurr1 = *px;
simon	0:1014af42efd9	310
simon	0:1014af42efd9	311	/* for sample 1 processing */
simon	0:1014af42efd9	312	/* f1(n) = f0(n) + K1 * g0(n-1) */
simon	0:1014af42efd9	313	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	314	/* g1(n) = f0(n) * K1 + g0(n-1) */
simon	0:1014af42efd9	315	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	316	/* save g1(n) in state buffer */
simon	0:1014af42efd9	317	*px++ = fcurr1;
simon	0:1014af42efd9	318
simon	0:1014af42efd9	319	/* f1(n) is saved in fcurr1
simon	0:1014af42efd9	320	for next stage processing */
simon	0:1014af42efd9	321	fcurr1 = fnext1;
simon	0:1014af42efd9	322
simon	0:1014af42efd9	323	stageCnt = (numStages - 1u);
simon	0:1014af42efd9	324
simon	0:1014af42efd9	325	/* stage loop */
simon	0:1014af42efd9	326	while(stageCnt > 0u)
simon	0:1014af42efd9	327	{
simon	0:1014af42efd9	328	/* read g2(n) from state buffer */
simon	0:1014af42efd9	329	gcurr1 = *px;
simon	0:1014af42efd9	330
simon	0:1014af42efd9	331	/* save g1(n) in state buffer */
simon	0:1014af42efd9	332	*px++ = gnext1;
simon	0:1014af42efd9	333
simon	0:1014af42efd9	334	/* Sample processing for K2, K3.... */
simon	0:1014af42efd9	335	/* f2(n) = f1(n) + K2 * g1(n-1) */
simon	0:1014af42efd9	336	fnext1 = (q31_t) (((q63_t) gcurr1 * (*pk)) >> 31) + fcurr1;
simon	0:1014af42efd9	337	/* g2(n) = f1(n) * K2 + g1(n-1) */
simon	0:1014af42efd9	338	gnext1 = (q31_t) (((q63_t) fcurr1 * (*pk++)) >> 31) + gcurr1;
simon	0:1014af42efd9	339
simon	0:1014af42efd9	340	/* f1(n) is saved in fcurr1
simon	0:1014af42efd9	341	for next stage processing */
simon	0:1014af42efd9	342	fcurr1 = fnext1;
simon	0:1014af42efd9	343
simon	0:1014af42efd9	344	stageCnt--;
simon	0:1014af42efd9	345
simon	0:1014af42efd9	346	}
simon	0:1014af42efd9	347
simon	0:1014af42efd9	348	/* y(n) = fN(n) */
simon	0:1014af42efd9	349	*pDst++ = fcurr1;
simon	0:1014af42efd9	350
simon	0:1014af42efd9	351	blkCnt--;
simon	0:1014af42efd9	352
simon	0:1014af42efd9	353	}
simon	0:1014af42efd9	354	}
simon	0:1014af42efd9	355
simon	0:1014af42efd9	356	/**
simon	0:1014af42efd9	357	* @} end of FIR_Lattice group
simon	0:1014af42efd9	358	*/

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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_fir_lattice_q31.c@0:1014af42efd9, 2011-03-10 (annotated)

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