arm_q15_to_float.c

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_q15_to_float.c  
00009 *  
00010 * Description:  Processing function for the Conversion from Q15 to float  
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  
00029 /**  
00030  * @ingroup groupSupport  
00031  */ 
00032  
00033 /**  
00034  * @defgroup q15_to_x  Convert 16-bit Integer value  
00035  */ 
00036  
00037 /**  
00038  * @addtogroup q15_to_x  
00039  * @{  
00040  */ 
00041  
00042  
00043  
00044  
00045 /**  
00046  * @brief  Converts the elements of the Q15 vector to floating-point vector.   
00047  * @param[in]       *pSrc points to the Q15 input vector  
00048  * @param[out]      *pDst points to the floating-point output vector 
00049  * @param[in]       blockSize length of the input vector  
00050  * @return none.  
00051  *  
00052  * \par Description:  
00053  *  
00054  * The equation used for the conversion process is:  
00055  * 
00056  * <pre>  
00057  *  pDst[n] = (float32_t) pSrc[n] / 32768;   0 <= n < blockSize.  
00058  * </pre>  
00059  * 
00060  */ 
00061  
00062  
00063 void arm_q15_to_float( 
00064   q15_t * pSrc, 
00065   float32_t * pDst, 
00066   uint32_t blockSize) 
00067 { 
00068   q15_t *pIn = pSrc;                             /* Src pointer */ 
00069   uint32_t blkCnt;                               /* loop counter */ 
00070  
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 = (float32_t) A / 32768 */ 
00080     /* convert from q15 to float and then store the results in the destination buffer */ 
00081     *pDst++ = ((float32_t) * pIn++ / 32768.0f); 
00082     *pDst++ = ((float32_t) * pIn++ / 32768.0f); 
00083     *pDst++ = ((float32_t) * pIn++ / 32768.0f); 
00084     *pDst++ = ((float32_t) * pIn++ / 32768.0f); 
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   while(blkCnt > 0u) 
00095   { 
00096     /* C = (float32_t) A / 32768 */ 
00097     /* convert from q15 to float and then store the results in the destination buffer */ 
00098     *pDst++ = ((float32_t) * pIn++ / 32768.0f); 
00099  
00100     /* Decrement the loop counter */ 
00101     blkCnt--; 
00102   } 
00103 } 
00104  
00105 /**  
00106  * @} end of q15_to_x group  
00107  */