/* ---------------------------------------------------------------------------- * Copyright (C) 2010 ARM Limited. All rights reserved. * * $Date: 29. November 2010 * $Revision: V1.0.3 * * Project: CMSIS DSP Library * Title: arm_q15_to_q7.c * * Description: Processing function for the Conversion from Q15 to Q7 * * Target Processor: Cortex-M4/Cortex-M3 * * Version 1.0.3 2010/11/29 * Re-organized the CMSIS folders and updated documentation. * * Version 1.0.2 2010/11/11 * Documentation updated. * * Version 1.0.1 2010/10/05 * Production release and review comments incorporated. * * Version 1.0.0 2010/09/20 * Production release and review comments incorporated. * ---------------------------------------------------------------------------- */ #include "arm_math.h" /** * @ingroup groupSupport */ /** * @addtogroup q15_to_x * @{ */ /** * @brief Converts the elements of the Q15 vector to Q7 vector. * @param[in] *pSrc points to the Q15 input vector * @param[out] *pDst points to the Q7 output vector * @param[in] blockSize length of the input vector * @return none. * * \par Description: * * The equation used for the conversion process is: * *
* pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize. ** */ void arm_q15_to_q7( q15_t * pSrc, q7_t * pDst, uint32_t blockSize) { q15_t *pIn = pSrc; /* Src pointer */ uint32_t blkCnt; /* loop counter */ /*loop Unrolling */ blkCnt = blockSize >> 2u; /* First part of the processing with loop unrolling. Compute 4 outputs at a time. ** a second loop below computes the remaining 1 to 3 samples. */ while(blkCnt > 0u) { /* C = (q7_t) A >> 8 */ /* convert from q15 to q7 and then store the results in the destination buffer */ *pDst++ = (q7_t) (*pIn++ >> 8); *pDst++ = (q7_t) (*pIn++ >> 8); *pDst++ = (q7_t) (*pIn++ >> 8); *pDst++ = (q7_t) (*pIn++ >> 8); /* Decrement the loop counter */ blkCnt--; } /* If the blockSize is not a multiple of 4, compute any remaining output samples here. ** No loop unrolling is used. */ blkCnt = blockSize % 0x4u; while(blkCnt > 0u) { /* C = (q7_t) A >> 8 */ /* convert from q15 to q7 and then store the results in the destination buffer */ *pDst++ = (q7_t) (*pIn++ >> 8); /* Decrement the loop counter */ blkCnt--; } } /** * @} end of q15_to_x group */