arm_float_to_q15.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_float_to_q15.c    
00009 *    
00010 * Description:  Converts the elements of the floating-point vector to Q15 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  * @addtogroup float_to_x    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @brief Converts the elements of the floating-point vector to Q15 vector.    
00054  * @param[in]       *pSrc points to the floating-point input vector    
00055  * @param[out]      *pDst points to the Q15 output vector   
00056  * @param[in]       blockSize length of the input vector    
00057  * @return none.    
00058  *    
00059  * \par Description:    
00060  * \par   
00061  * The equation used for the conversion process is:    
00062  * <pre>    
00063  *  pDst[n] = (q15_t)(pSrc[n] * 32768);   0 <= n < blockSize.    
00064  * </pre>    
00065  * \par Scaling and Overflow Behavior:    
00066  * \par    
00067  * The function uses saturating arithmetic.    
00068  * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.    
00069  * \note   
00070  * In order to apply rounding, the library should be rebuilt with the ROUNDING macro     
00071  * defined in the preprocessor section of project options.     
00072  *    
00073  */
00074 
00075 
00076 void arm_float_to_q15(
00077   float32_t * pSrc,
00078   q15_t * pDst,
00079   uint32_t blockSize)
00080 {
00081   float32_t *pIn = pSrc;                         /* Src pointer */
00082   uint32_t blkCnt;                               /* loop counter */
00083 
00084 #ifdef ARM_MATH_ROUNDING
00085 
00086   float32_t in;
00087 
00088 #endif /*      #ifdef ARM_MATH_ROUNDING        */
00089 
00090 #ifndef ARM_MATH_CM0_FAMILY
00091 
00092   /* Run the below code for Cortex-M4 and Cortex-M3 */
00093 
00094   /*loop Unrolling */
00095   blkCnt = blockSize >> 2u;
00096 
00097   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
00098    ** a second loop below computes the remaining 1 to 3 samples. */
00099   while(blkCnt > 0u)
00100   {
00101 
00102 #ifdef ARM_MATH_ROUNDING
00103     /* C = A * 32768 */
00104     /* convert from float to q15 and then store the results in the destination buffer */
00105     in = *pIn++;
00106     in = (in * 32768.0f);
00107     in += in > 0.0f ? 0.5f : -0.5f;
00108     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00109 
00110     in = *pIn++;
00111     in = (in * 32768.0f);
00112     in += in > 0.0f ? 0.5f : -0.5f;
00113     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00114 
00115     in = *pIn++;
00116     in = (in * 32768.0f);
00117     in += in > 0.0f ? 0.5f : -0.5f;
00118     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00119 
00120     in = *pIn++;
00121     in = (in * 32768.0f);
00122     in += in > 0.0f ? 0.5f : -0.5f;
00123     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00124 
00125 #else
00126 
00127     /* C = A * 32768 */
00128     /* convert from float to q15 and then store the results in the destination buffer */
00129     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00130     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00131     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00132     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00133 
00134 #endif /*      #ifdef ARM_MATH_ROUNDING        */
00135 
00136     /* Decrement the loop counter */
00137     blkCnt--;
00138   }
00139 
00140   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
00141    ** No loop unrolling is used. */
00142   blkCnt = blockSize % 0x4u;
00143 
00144   while(blkCnt > 0u)
00145   {
00146 
00147 #ifdef ARM_MATH_ROUNDING
00148     /* C = A * 32768 */
00149     /* convert from float to q15 and then store the results in the destination buffer */
00150     in = *pIn++;
00151     in = (in * 32768.0f);
00152     in += in > 0.0f ? 0.5f : -0.5f;
00153     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00154 
00155 #else
00156 
00157     /* C = A * 32768 */
00158     /* convert from float to q15 and then store the results in the destination buffer */
00159     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00160 
00161 #endif /*      #ifdef ARM_MATH_ROUNDING        */
00162 
00163     /* Decrement the loop counter */
00164     blkCnt--;
00165   }
00166 
00167 
00168 #else
00169 
00170   /* Run the below code for Cortex-M0 */
00171 
00172   /* Loop over blockSize number of values */
00173   blkCnt = blockSize;
00174 
00175   while(blkCnt > 0u)
00176   {
00177 
00178 #ifdef ARM_MATH_ROUNDING
00179     /* C = A * 32768 */
00180     /* convert from float to q15 and then store the results in the destination buffer */
00181     in = *pIn++;
00182     in = (in * 32768.0f);
00183     in += in > 0 ? 0.5f : -0.5f;
00184     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16));
00185 
00186 #else
00187 
00188     /* C = A * 32768 */
00189     /* convert from float to q15 and then store the results in the destination buffer */
00190     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16);
00191 
00192 #endif /*      #ifdef ARM_MATH_ROUNDING        */
00193 
00194     /* Decrement the loop counter */
00195     blkCnt--;
00196   }
00197 
00198 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
00199 
00200 }
00201 
00202 /**    
00203  * @} end of float_to_x group    
00204  */