WebSVN – dashGPS – Blame – /trunk/Drivers/CMSIS/DSP/Source/SupportFunctions/arm_float_to_q15.c

Rev	Author	Line No.	Line
2	mjames	1	/* ----------------------------------------------------------------------
		2	* Project: CMSIS DSP Library
		3	* Title: arm_float_to_q15.c
		4	* Description: Converts the elements of the floating-point vector to Q15 vector
		5	*
		6	* $Date: 27. January 2017
		7	* $Revision: V.1.5.1
		8	*
		9	* Target Processor: Cortex-M cores
		10	* -------------------------------------------------------------------- */
		11	/*
		12	* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
		13	*
		14	* SPDX-License-Identifier: Apache-2.0
		15	*
		16	* Licensed under the Apache License, Version 2.0 (the License); you may
		17	* not use this file except in compliance with the License.
		18	* You may obtain a copy of the License at
		19	*
		20	* www.apache.org/licenses/LICENSE-2.0
		21	*
		22	* Unless required by applicable law or agreed to in writing, software
		23	* distributed under the License is distributed on an AS IS BASIS, WITHOUT
		24	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		25	* See the License for the specific language governing permissions and
		26	* limitations under the License.
		27	*/
		28
		29	#include "arm_math.h"
		30
		31	/**
		32	* @ingroup groupSupport
		33	*/
		34
		35	/**
		36	* @addtogroup float_to_x
		37	* @{
		38	*/
		39
		40	/**
		41	* @brief Converts the elements of the floating-point vector to Q15 vector.
		42	* @param[in] *pSrc points to the floating-point input vector
		43	* @param[out] *pDst points to the Q15 output vector
		44	* @param[in] blockSize length of the input vector
		45	* @return none.
		46	*
		47	* \par Description:
		48	* \par
		49	* The equation used for the conversion process is:
		50	* <pre>
		51	* pDst[n] = (q15_t)(pSrc[n] * 32768); 0 <= n < blockSize.
		52	* </pre>
		53	* \par Scaling and Overflow Behavior:
		54	* \par
		55	* The function uses saturating arithmetic.
		56	* Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
		57	* \note
		58	* In order to apply rounding, the library should be rebuilt with the ROUNDING macro
		59	* defined in the preprocessor section of project options.
		60	*
		61	*/
		62
		63
		64	void arm_float_to_q15(
		65	float32_t * pSrc,
		66	q15_t * pDst,
		67	uint32_t blockSize)
		68	{
		69	float32_t pIn = pSrc; / Src pointer */
		70	uint32_t blkCnt; /* loop counter */
		71
		72	#ifdef ARM_MATH_ROUNDING
		73
		74	float32_t in;
		75
		76	#endif /* #ifdef ARM_MATH_ROUNDING */
		77
		78	#if defined (ARM_MATH_DSP)
		79
		80	/* Run the below code for Cortex-M4 and Cortex-M3 */
		81
		82	/loop Unrolling /
		83	blkCnt = blockSize >> 2U;
		84
		85	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
		86	** a second loop below computes the remaining 1 to 3 samples. */
		87	while (blkCnt > 0U)
		88	{
		89
		90	#ifdef ARM_MATH_ROUNDING
		91	/* C = A * 32768 */
		92	/* convert from float to q15 and then store the results in the destination buffer */
		93	in = *pIn++;
		94	in = (in * 32768.0f);
		95	in += in > 0.0f ? 0.5f : -0.5f;
		96	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		97
		98	in = *pIn++;
		99	in = (in * 32768.0f);
		100	in += in > 0.0f ? 0.5f : -0.5f;
		101	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		102
		103	in = *pIn++;
		104	in = (in * 32768.0f);
		105	in += in > 0.0f ? 0.5f : -0.5f;
		106	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		107
		108	in = *pIn++;
		109	in = (in * 32768.0f);
		110	in += in > 0.0f ? 0.5f : -0.5f;
		111	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		112
		113	#else
		114
		115	/* C = A * 32768 */
		116	/* convert from float to q15 and then store the results in the destination buffer */
		117	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		118	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		119	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		120	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		121
		122	#endif /* #ifdef ARM_MATH_ROUNDING */
		123
		124	/* Decrement the loop counter */
		125	blkCnt--;
		126	}
		127
		128	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
		129	** No loop unrolling is used. */
		130	blkCnt = blockSize % 0x4U;
		131
		132	while (blkCnt > 0U)
		133	{
		134
		135	#ifdef ARM_MATH_ROUNDING
		136	/* C = A * 32768 */
		137	/* convert from float to q15 and then store the results in the destination buffer */
		138	in = *pIn++;
		139	in = (in * 32768.0f);
		140	in += in > 0.0f ? 0.5f : -0.5f;
		141	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		142
		143	#else
		144
		145	/* C = A * 32768 */
		146	/* convert from float to q15 and then store the results in the destination buffer */
		147	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		148
		149	#endif /* #ifdef ARM_MATH_ROUNDING */
		150
		151	/* Decrement the loop counter */
		152	blkCnt--;
		153	}
		154
		155
		156	#else
		157
		158	/* Run the below code for Cortex-M0 */
		159
		160	/* Loop over blockSize number of values */
		161	blkCnt = blockSize;
		162
		163	while (blkCnt > 0U)
		164	{
		165
		166	#ifdef ARM_MATH_ROUNDING
		167	/* C = A * 32768 */
		168	/* convert from float to q15 and then store the results in the destination buffer */
		169	in = *pIn++;
		170	in = (in * 32768.0f);
		171	in += in > 0 ? 0.5f : -0.5f;
		172	*pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
		173
		174	#else
		175
		176	/* C = A * 32768 */
		177	/* convert from float to q15 and then store the results in the destination buffer */
		178	pDst++ = (q15_t) __SSAT((q31_t) (pIn++ * 32768.0f), 16);
		179
		180	#endif /* #ifdef ARM_MATH_ROUNDING */
		181
		182	/* Decrement the loop counter */
		183	blkCnt--;
		184	}
		185
		186	#endif /* #if defined (ARM_MATH_DSP) */
		187
		188	}
		189
		190	/**
		191	* @} end of float_to_x group
		192	*/

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