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src/Cortex-M4-M3/FilteringFunctions/arm_fir_q7.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_q7.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Q7 FIR 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 0.0.5 2010/04/26
simon	0:1014af42efd9	27	* incorporated review comments and updated with latest CMSIS layer
simon	0:1014af42efd9	28	*
simon	0:1014af42efd9	29	* Version 0.0.3 2010/03/10
simon	0:1014af42efd9	30	* Initial version
simon	0:1014af42efd9	31	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	32
simon	0:1014af42efd9	33	#include "arm_math.h"
simon	0:1014af42efd9	34
simon	0:1014af42efd9	35	/**
simon	0:1014af42efd9	36	* @ingroup groupFilters
simon	0:1014af42efd9	37	*/
simon	0:1014af42efd9	38
simon	0:1014af42efd9	39	/**
simon	0:1014af42efd9	40	* @addtogroup FIR
simon	0:1014af42efd9	41	* @{
simon	0:1014af42efd9	42	*/
simon	0:1014af42efd9	43
simon	0:1014af42efd9	44	/**
simon	0:1014af42efd9	45	* @param[in] *S points to an instance of the Q7 FIR filter structure.
simon	0:1014af42efd9	46	* @param[in] *pSrc points to the block of input data.
simon	0:1014af42efd9	47	* @param[out] *pDst points to the block of output data.
simon	0:1014af42efd9	48	* @param[in] blockSize number of samples to process per call.
simon	0:1014af42efd9	49	* @return none.
simon	0:1014af42efd9	50	*
simon	0:1014af42efd9	51	* <b>Scaling and Overflow Behavior:</b>
simon	0:1014af42efd9	52	* \par
simon	0:1014af42efd9	53	* The function is implemented using a 32-bit internal accumulator.
simon	0:1014af42efd9	54	* Both coefficients and state variables are represented in 1.7 format and multiplications yield a 2.14 result.
simon	0:1014af42efd9	55	* The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
simon	0:1014af42efd9	56	* There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
simon	0:1014af42efd9	57	* The accumulator is converted to 18.7 format by discarding the low 7 bits.
simon	0:1014af42efd9	58	* Finally, the result is truncated to 1.7 format.
simon	0:1014af42efd9	59	*/
simon	0:1014af42efd9	60
simon	0:1014af42efd9	61	void arm_fir_q7(
simon	0:1014af42efd9	62	const arm_fir_instance_q7 * S,
simon	0:1014af42efd9	63	q7_t * pSrc,
simon	0:1014af42efd9	64	q7_t * pDst,
simon	0:1014af42efd9	65	uint32_t blockSize)
simon	0:1014af42efd9	66	{
simon	0:1014af42efd9	67	uint32_t numTaps = S->numTaps; /* Number of taps in the filter */
simon	0:1014af42efd9	68	uint32_t i, blkCnt; /* Loop counters */
simon	0:1014af42efd9	69	q7_t pState = S->pState; / State pointer */
simon	0:1014af42efd9	70	q7_t pCoeffs = S->pCoeffs; / Coefficient pointer */
simon	0:1014af42efd9	71	q7_t px, pb; /* Temporary pointers to state and coeff */
simon	0:1014af42efd9	72	q31_t acc = 0; /* Accumlator */
simon	0:1014af42efd9	73	q31_t input1, input2; /* Temporary variables to store input */
simon	0:1014af42efd9	74	q15_t in1, in2; /* Temporary variables to store input */
simon	0:1014af42efd9	75	q7_t pStateCurnt; / Points to the current sample of the state */
simon	0:1014af42efd9	76
simon	0:1014af42efd9	77
simon	0:1014af42efd9	78	/* S->pState points to state array which contains previous frame (numTaps - 1) samples */
simon	0:1014af42efd9	79	/* pStateCurnt points to the location where the new input data should be written */
simon	0:1014af42efd9	80	pStateCurnt = S->pState + (numTaps - 1u);
simon	0:1014af42efd9	81
simon	0:1014af42efd9	82	i = blockSize >> 2u;
simon	0:1014af42efd9	83
simon	0:1014af42efd9	84	/* Copy four new input samples into the state buffer.
simon	0:1014af42efd9	85	** Use 32-bit SIMD to move the four 8-bit data. Only requires one copy for every four samples. */
simon	0:1014af42efd9	86	while(i > 0u)
simon	0:1014af42efd9	87	{
simon	0:1014af42efd9	88	__SIMD32(pStateCurnt)++ = __SIMD32(pSrc)++;
simon	0:1014af42efd9	89	i--;
simon	0:1014af42efd9	90	}
simon	0:1014af42efd9	91
simon	0:1014af42efd9	92	i = blockSize % 0x4u;
simon	0:1014af42efd9	93
simon	0:1014af42efd9	94	/* Copy remining samples into the state buffer. */
simon	0:1014af42efd9	95	while(i > 0u)
simon	0:1014af42efd9	96	{
simon	0:1014af42efd9	97	pStateCurnt++ = pSrc++;
simon	0:1014af42efd9	98	i--;
simon	0:1014af42efd9	99	}
simon	0:1014af42efd9	100
simon	0:1014af42efd9	101	blkCnt = blockSize;
simon	0:1014af42efd9	102
simon	0:1014af42efd9	103	/* Perform filtering upto BlockSize - BlockSize%4 */
simon	0:1014af42efd9	104	while(blkCnt > 0u)
simon	0:1014af42efd9	105	{
simon	0:1014af42efd9	106	/* Set accumulator to zero */
simon	0:1014af42efd9	107	acc = 0;
simon	0:1014af42efd9	108
simon	0:1014af42efd9	109	/* Initialize state pointer of type q7 */
simon	0:1014af42efd9	110	px = pState;
simon	0:1014af42efd9	111
simon	0:1014af42efd9	112	/* Initialize coeff pointer of type q7 */
simon	0:1014af42efd9	113	pb = pCoeffs;
simon	0:1014af42efd9	114
simon	0:1014af42efd9	115	i = numTaps >> 2u;
simon	0:1014af42efd9	116
simon	0:1014af42efd9	117	/* Loop over the number of taps. Unroll by a factor of 4.
simon	0:1014af42efd9	118	** Repeat until we've computed numTaps-4 coefficients. */
simon	0:1014af42efd9	119	while(i > 0u)
simon	0:1014af42efd9	120	{
simon	0:1014af42efd9	121	/* Reading two inputs of state buffer and packing */
simon	0:1014af42efd9	122	in1 = (q15_t) * px++;
simon	0:1014af42efd9	123	in2 = (q15_t) * px++;
simon	0:1014af42efd9	124	input1 = ((q31_t) in1 & 0x0000FFFF) \| ((q31_t) in2 << 16);
simon	0:1014af42efd9	125
simon	0:1014af42efd9	126	/* Reading two inputs of coefficient buffer and packing */
simon	0:1014af42efd9	127	in1 = (q15_t) * pb++;
simon	0:1014af42efd9	128	in2 = (q15_t) * pb++;
simon	0:1014af42efd9	129	input2 = ((q31_t) in1 & 0x0000FFFF) \| ((q31_t) in2 << 16);
simon	0:1014af42efd9	130
simon	0:1014af42efd9	131	/* Perform Multiply and accumlation of 2 packed inputs and coefficients using SMLALD and store the result in accumlator. */
simon	0:1014af42efd9	132	acc = __SMLAD(input1, input2, acc);
simon	0:1014af42efd9	133
simon	0:1014af42efd9	134	/* Reading two inputs of state buffer and packing */
simon	0:1014af42efd9	135	in1 = (q15_t) * px++;
simon	0:1014af42efd9	136	in2 = (q15_t) * px++;
simon	0:1014af42efd9	137	input1 = ((q31_t) in1 & 0x0000FFFF) \| ((q31_t) in2 << 16);
simon	0:1014af42efd9	138
simon	0:1014af42efd9	139	/* Reading two inputs of coefficient buffer and packing */
simon	0:1014af42efd9	140	in1 = (q15_t) * pb++;
simon	0:1014af42efd9	141	in2 = (q15_t) * pb++;
simon	0:1014af42efd9	142	input2 = ((q31_t) in1 & 0x0000FFFF) \| ((q31_t) in2 << 16);
simon	0:1014af42efd9	143
simon	0:1014af42efd9	144	/* Perform Multiply and accumlation of 2 packed inputs and coefficients using SMLALD and store the result in accumlator. */
simon	0:1014af42efd9	145	acc = __SMLAD(input1, input2, acc);
simon	0:1014af42efd9	146
simon	0:1014af42efd9	147	/* Decrement the tap loop counter */
simon	0:1014af42efd9	148	i--;
simon	0:1014af42efd9	149	}
simon	0:1014af42efd9	150
simon	0:1014af42efd9	151	i = numTaps % 0x4u;
simon	0:1014af42efd9	152
simon	0:1014af42efd9	153	/* If the filter length is not a multiple of 4, compute the remaining filter taps */
simon	0:1014af42efd9	154	while(i > 0u)
simon	0:1014af42efd9	155	{
simon	0:1014af42efd9	156	acc = __SMLAD(px++, pb++, acc);
simon	0:1014af42efd9	157	i--;
simon	0:1014af42efd9	158
simon	0:1014af42efd9	159	}
simon	0:1014af42efd9	160
simon	0:1014af42efd9	161	/* Saturate output */
simon	0:1014af42efd9	162	acc = __SSAT((acc >> 7), 8);
simon	0:1014af42efd9	163
simon	0:1014af42efd9	164	/Store filter output /
simon	0:1014af42efd9	165	*pDst++ = (q7_t) (acc);
simon	0:1014af42efd9	166
simon	0:1014af42efd9	167	/* Advance the state pointer by 1 to process the next sample */
simon	0:1014af42efd9	168	pState = pState + 1;
simon	0:1014af42efd9	169
simon	0:1014af42efd9	170	/* Decrement the loop counter */
simon	0:1014af42efd9	171	blkCnt--;
simon	0:1014af42efd9	172	}
simon	0:1014af42efd9	173
simon	0:1014af42efd9	174	/* Processing is complete.
simon	0:1014af42efd9	175	** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
simon	0:1014af42efd9	176	** This prepares the state buffer for the next function call. */
simon	0:1014af42efd9	177
simon	0:1014af42efd9	178	/* Points to the start of the state buffer */
simon	0:1014af42efd9	179	pStateCurnt = S->pState;
simon	0:1014af42efd9	180
simon	0:1014af42efd9	181	/* Calculation of count for copying integer writes */
simon	0:1014af42efd9	182	i = (numTaps - 1u) >> 2u;
simon	0:1014af42efd9	183
simon	0:1014af42efd9	184	/* Copy four values using integer pointer */
simon	0:1014af42efd9	185	while(i > 0u)
simon	0:1014af42efd9	186	{
simon	0:1014af42efd9	187	__SIMD32(pStateCurnt)++ = __SIMD32(pState)++;
simon	0:1014af42efd9	188
simon	0:1014af42efd9	189	i--;
simon	0:1014af42efd9	190
simon	0:1014af42efd9	191	}
simon	0:1014af42efd9	192
simon	0:1014af42efd9	193	/* Calculation of count for remaining q7_t data */
simon	0:1014af42efd9	194	i = (numTaps - 1u) % 0x4u;
simon	0:1014af42efd9	195
simon	0:1014af42efd9	196	/* Copy of remaining q7_t data */
simon	0:1014af42efd9	197	while(i > 0u)
simon	0:1014af42efd9	198	{
simon	0:1014af42efd9	199	pStateCurnt++ = pState++;
simon	0:1014af42efd9	200	i--;
simon	0:1014af42efd9	201	}
simon	0:1014af42efd9	202
simon	0:1014af42efd9	203	}
simon	0:1014af42efd9	204
simon	0:1014af42efd9	205	/**
simon	0:1014af42efd9	206	* @} end of FIR group
simon	0:1014af42efd9	207	*/

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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_q7.c@0:1014af42efd9, 2011-03-10 (annotated)

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