147 lines
3.6 KiB
C
147 lines
3.6 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_q15_to_q7.c
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* Description: Converts the elements of the Q15 vector to Q7 vector
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*
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* $Date: 18. March 2019
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* $Revision: V1.6.0
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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@ingroup groupSupport
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*/
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/**
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@addtogroup q15_to_x
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@{
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*/
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/**
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@brief Converts the elements of the Q15 vector to Q7 vector.
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@param[in] pSrc points to the Q15 input vector
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@param[out] pDst points to the Q7 output vector
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@param[in] blockSize number of samples in each vector
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@return none
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@par Details
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The equation used for the conversion process is:
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<pre>
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pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize.
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</pre>
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*/
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void arm_q15_to_q7(
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const q15_t * pSrc,
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q7_t * pDst,
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uint32_t blockSize)
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{
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uint32_t blkCnt; /* Loop counter */
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const q15_t *pIn = pSrc; /* Source pointer */
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#if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
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q31_t in1, in2;
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q31_t out1, out2;
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#endif
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#if defined (ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U)
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{
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/* C = (q7_t) A >> 8 */
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/* Convert from q15 to q7 and store result in destination buffer */
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#if defined (ARM_MATH_DSP)
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in1 = read_q15x2_ia ((q15_t **) &pIn);
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in2 = read_q15x2_ia ((q15_t **) &pIn);
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#ifndef ARM_MATH_BIG_ENDIAN
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out1 = __PKHTB(in2, in1, 16);
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out2 = __PKHBT(in2, in1, 16);
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#else
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out1 = __PKHTB(in1, in2, 16);
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out2 = __PKHBT(in1, in2, 16);
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#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
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/* rotate packed value by 24 */
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out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
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/* anding with 0xff00ff00 to get two 8 bit values */
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out1 = out1 & 0xFF00FF00;
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/* anding with 0x00ff00ff to get two 8 bit values */
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out2 = out2 & 0x00FF00FF;
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/* oring two values(contains two 8 bit values) to get four packed 8 bit values */
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out1 = out1 | out2;
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/* store 4 samples at a time to destiantion buffer */
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write_q7x4_ia (&pDst, out1);
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#else
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*pDst++ = (q7_t) (*pIn++ >> 8);
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*pDst++ = (q7_t) (*pIn++ >> 8);
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*pDst++ = (q7_t) (*pIn++ >> 8);
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*pDst++ = (q7_t) (*pIn++ >> 8);
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#endif /* #if defined (ARM_MATH_DSP) */
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U)
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{
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/* C = (q7_t) A >> 8 */
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/* Convert from q15 to q7 and store result in destination buffer */
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*pDst++ = (q7_t) (*pIn++ >> 8);
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/* Decrement loop counter */
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blkCnt--;
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}
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}
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/**
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@} end of q15_to_x group
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*/
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