arm_q31_to_float.c

00001 /* ----------------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015
00005 * $Revision:    V.1.4.5  
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_q31_to_float.c    
00009 *    
00010 * Description:  Converts the elements of the Q31 vector to floating-point vector.      
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.  
00039 * ---------------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupSupport    
00045  */
00046 
00047 /**    
00048  * @defgroup q31_to_x  Convert 32-bit Integer value    
00049  */
00050 
00051 /**    
00052  * @addtogroup q31_to_x    
00053  * @{    
00054  */
00055 
00056 /**    
00057  * @brief Converts the elements of the Q31 vector to floating-point vector.    
00058  * @param[in]       *pSrc points to the Q31 input vector    
00059  * @param[out]      *pDst points to the floating-point output vector   
00060  * @param[in]       blockSize length of the input vector    
00061  * @return none.    
00062  *    
00063  * \par Description:    
00064  *    
00065  * The equation used for the conversion process is:    
00066  *   
00067  * <pre>    
00068  *  pDst[n] = (float32_t) pSrc[n] / 2147483648;   0 <= n < blockSize.    
00069  * </pre>    
00070  *   
00071  */
00072 
00073 
00074 void arm_q31_to_float(
00075   q31_t * pSrc,
00076   float32_t * pDst,
00077   uint32_t blockSize)
00078 {
00079   q31_t *pIn = pSrc;                             /* Src pointer */
00080   uint32_t blkCnt;                               /* loop counter */
00081 
00082 
00083 #ifndef ARM_MATH_CM0_FAMILY
00084 
00085   /* Run the below code for Cortex-M4 and Cortex-M3 */
00086 
00087   /*loop Unrolling */
00088   blkCnt = blockSize >> 2u;
00089 
00090   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
00091    ** a second loop below computes the remaining 1 to 3 samples. */
00092   while(blkCnt > 0u)
00093   {
00094     /* C = (float32_t) A / 2147483648 */
00095     /* convert from q31 to float and then store the results in the destination buffer */
00096     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f);
00097     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f);
00098     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f);
00099     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f);
00100 
00101     /* Decrement the loop counter */
00102     blkCnt--;
00103   }
00104 
00105   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
00106    ** No loop unrolling is used. */
00107   blkCnt = blockSize % 0x4u;
00108 
00109 #else
00110 
00111   /* Run the below code for Cortex-M0 */
00112 
00113   /* Loop over blockSize number of values */
00114   blkCnt = blockSize;
00115 
00116 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
00117 
00118   while(blkCnt > 0u)
00119   {
00120     /* C = (float32_t) A / 2147483648 */
00121     /* convert from q31 to float and then store the results in the destination buffer */
00122     *pDst++ = ((float32_t) * pIn++ / 2147483648.0f);
00123 
00124     /* Decrement the loop counter */
00125     blkCnt--;
00126   }
00127 }
00128 
00129 /**    
00130  * @} end of q31_to_x group    
00131  */