arm_q31_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_q31_to_float.c  
00009 *  
00010 * Description:  Processing function for the Conversion from Q31 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 q31_to_x  Convert 32-bit Integer value  
00035  */ 
00036  
00037 /**  
00038  * @addtogroup q31_to_x  
00039  * @{  
00040  */ 
00041  
00042 /**  
00043  * @brief Converts the elements of the Q31 vector to floating-point vector.  
00044  * @param[in]       *pSrc points to the Q31 input vector  
00045  * @param[out]      *pDst points to the floating-point output vector 
00046  * @param[in]       blockSize length of the input vector  
00047  * @return none.  
00048  *  
00049  * \par Description:  
00050  *  
00051  * The equation used for the conversion process is:  
00052  * 
00053  * <pre>  
00054  *  pDst[n] = (float32_t) pSrc[n] / 2147483648;   0 <= n < blockSize.  
00055  * </pre>  
00056  * 
00057  */ 
00058  
00059  
00060 void arm_q31_to_float( 
00061   q31_t * pSrc, 
00062   float32_t * pDst, 
00063   uint32_t blockSize) 
00064 { 
00065   q31_t *pIn = pSrc;                             /* Src pointer */ 
00066   uint32_t blkCnt;                               /* loop counter */ 
00067  
00068  
00069   /*loop Unrolling */ 
00070   blkCnt = blockSize >> 2u; 
00071  
00072   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00073    ** a second loop below computes the remaining 1 to 3 samples. */ 
00074   while(blkCnt > 0u) 
00075   { 
00076     /* C = (float32_t) A / 2147483648 */ 
00077     /* convert from q31 to float and then store the results in the destination buffer */ 
00078     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f); 
00079     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f); 
00080     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f); 
00081     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f); 
00082  
00083     /* Decrement the loop counter */ 
00084     blkCnt--; 
00085   } 
00086  
00087   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00088    ** No loop unrolling is used. */ 
00089   blkCnt = blockSize % 0x4u; 
00090  
00091   while(blkCnt > 0u) 
00092   { 
00093     /* C = (float32_t) A / 2147483648 */ 
00094     /* convert from q31 to float and then store the results in the destination buffer */ 
00095     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f); 
00096  
00097     /* Decrement the loop counter */ 
00098     blkCnt--; 
00099   } 
00100 } 
00101  
00102 /**  
00103  * @} end of q31_to_x group  
00104  */