CMSIS DSP Software Library: arm_q15_to_q7.c Source File

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# arm_q15_to_q7.c

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    00001 /* ----------------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_q15_to_q7.c
    00009 *
    00010 * Description:  Converts the elements of the Q15 vector to Q7 vector.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated.
    00028 * ---------------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00060 void arm_q15_to_q7(
    00061   q15_t * pSrc,
    00062   q7_t * pDst,
    00063   uint32_t blockSize)
    00064 {
    00065   q15_t *pIn = pSrc;                             /* Src pointer */
    00066   uint32_t blkCnt;                               /* loop counter */
    00067
    00068 #ifndef ARM_MATH_CM0
    00069
    00070   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00071
    00072   /*loop Unrolling */
    00073   blkCnt = blockSize >> 2u;
    00074
    00075   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00076    ** a second loop below computes the remaining 1 to 3 samples. */
    00077   while(blkCnt > 0u)
    00078   {
    00079     /* C = (q7_t) A >> 8 */
    00080     /* convert from q15 to q7 and then store the results in the destination buffer */
    00081     *pDst++ = (q7_t) (*pIn++ >> 8);
    00082     *pDst++ = (q7_t) (*pIn++ >> 8);
    00083     *pDst++ = (q7_t) (*pIn++ >> 8);
    00084     *pDst++ = (q7_t) (*pIn++ >> 8);
    00085
    00086     /* Decrement the loop counter */
    00087     blkCnt--;
    00088   }
    00089
    00090   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00091    ** No loop unrolling is used. */
    00092   blkCnt = blockSize % 0x4u;
    00093
    00094 #else
    00095
    00096   /* Run the below code for Cortex-M0 */
    00097
    00098   /* Loop over blockSize number of values */
    00099   blkCnt = blockSize;
    00100
    00101 #endif /* #ifndef ARM_MATH_CM0 */
    00102
    00103   while(blkCnt > 0u)
    00104   {
    00105     /* C = (q7_t) A >> 8 */
    00106     /* convert from q15 to q7 and then store the results in the destination buffer */
    00107     *pDst++ = (q7_t) (*pIn++ >> 8);
    00108
    00109     /* Decrement the loop counter */
    00110     blkCnt--;
    00111   }
    00112
    00113 }
    00114

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