CMSIS DSP Software Library: arm_q31_to_q15.c Source File
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arm_q31_to_q15.c
Go to the documentation of this file.00001 /* ----------------------------------------------------------------------------
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
00003 *
00004 * $Date: 29. November 2010
00005 * $Revision: V1.0.3
00006 *
00007 * Project: CMSIS DSP Library
00008 * Title: arm_q31_to_q15.c
00009 *
00010 * Description: Processing function for the Conversion from Q31 to Q15
00011 *
00012 * Target Processor: Cortex-M4/Cortex-M3
00013 *
00014 * Version 1.0.3 2010/11/29
00015 * Re-organized the CMSIS folders and updated documentation.
00016 *
00017 * Version 1.0.2 2010/11/11
00018 * Documentation updated.
00019 *
00020 * Version 1.0.1 2010/10/05
00021 * Production release and review comments incorporated.
00022 *
00023 * Version 1.0.0 2010/09/20
00024 * Production release and review comments incorporated.
00025 * ---------------------------------------------------------------------------- */
00026
00027 #include "arm_math.h"
00028
00056 void arm_q31_to_q15(
00057 q31_t * pSrc,
00058 q15_t * pDst,
00059 uint32_t blockSize)
00060 {
00061 q31_t *pIn = pSrc; /* Src pointer */
00062 uint32_t blkCnt; /* loop counter */
00063
00064 /*loop Unrolling */
00065 blkCnt = blockSize >> 2u;
00066
00067 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
00068 ** a second loop below computes the remaining 1 to 3 samples. */
00069 while(blkCnt > 0u)
00070 {
00071 /* C = (q15_t) A >> 16 */
00072 /* convert from q31 to q15 and then store the results in the destination buffer */
00073 *pDst++ = (q15_t) (*pIn++ >> 16);
00074 *pDst++ = (q15_t) (*pIn++ >> 16);
00075 *pDst++ = (q15_t) (*pIn++ >> 16);
00076 *pDst++ = (q15_t) (*pIn++ >> 16);
00077
00078 /* Decrement the loop counter */
00079 blkCnt--;
00080 }
00081
00082 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
00083 ** No loop unrolling is used. */
00084 blkCnt = blockSize % 0x4u;
00085
00086 while(blkCnt > 0u)
00087 {
00088 /* C = (q15_t) A >> 16 */
00089 /* convert from q31 to q15 and then store the results in the destination buffer */
00090 *pDst++ = (q15_t) (*pIn++ >> 16);
00091
00092 /* Decrement the loop counter */
00093 blkCnt--;
00094 }
00095
00096 }
00097
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