arm_q15_to_float.c

00001 /* ----------------------------------------------------------------------------    
00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        17. January 2013 
00005 * $Revision:    V1.4.1  
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_q15_to_float.c    
00009 *    
00010 * Description:  Converts the elements of the Q15 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 q15_to_x  Convert 16-bit Integer value    
00049  */
00050 
00051 /**    
00052  * @addtogroup q15_to_x    
00053  * @{    
00054  */
00055 
00056 
00057 
00058 
00059 /**    
00060  * @brief  Converts the elements of the Q15 vector to floating-point vector.     
00061  * @param[in]       *pSrc points to the Q15 input vector    
00062  * @param[out]      *pDst points to the floating-point output vector   
00063  * @param[in]       blockSize length of the input vector    
00064  * @return none.    
00065  *    
00066  * \par Description:    
00067  *    
00068  * The equation used for the conversion process is:    
00069  *   
00070  * <pre>    
00071  *  pDst[n] = (float32_t) pSrc[n] / 32768;   0 <= n < blockSize.    
00072  * </pre>    
00073  *   
00074  */
00075 
00076 
00077 void arm_q15_to_float(
00078   q15_t * pSrc,
00079   float32_t * pDst,
00080   uint32_t blockSize)
00081 {
00082   q15_t *pIn = pSrc;                             /* Src pointer */
00083   uint32_t blkCnt;                               /* loop counter */
00084 
00085 
00086 #ifndef ARM_MATH_CM0_FAMILY
00087 
00088   /* Run the below code for Cortex-M4 and Cortex-M3 */
00089 
00090   /*loop Unrolling */
00091   blkCnt = blockSize >> 2u;
00092 
00093   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
00094    ** a second loop below computes the remaining 1 to 3 samples. */
00095   while(blkCnt > 0u)
00096   {
00097     /* C = (float32_t) A / 32768 */
00098     /* convert from q15 to float and then store the results in the destination buffer */
00099     *pDst++ = ((float32_t) * pIn++ / 32768.0f);
00100     *pDst++ = ((float32_t) * pIn++ / 32768.0f);
00101     *pDst++ = ((float32_t) * pIn++ / 32768.0f);
00102     *pDst++ = ((float32_t) * pIn++ / 32768.0f);
00103 
00104     /* Decrement the loop counter */
00105     blkCnt--;
00106   }
00107 
00108   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
00109    ** No loop unrolling is used. */
00110   blkCnt = blockSize % 0x4u;
00111 
00112 #else
00113 
00114   /* Run the below code for Cortex-M0 */
00115 
00116   /* Loop over blockSize number of values */
00117   blkCnt = blockSize;
00118 
00119 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
00120 
00121   while(blkCnt > 0u)
00122   {
00123     /* C = (float32_t) A / 32768 */
00124     /* convert from q15 to float and then store the results in the destination buffer */
00125     *pDst++ = ((float32_t) * pIn++ / 32768.0f);
00126 
00127     /* Decrement the loop counter */
00128     blkCnt--;
00129   }
00130 }
00131 
00132 /**    
00133  * @} end of q15_to_x group    
00134  */