arm_float_to_q15.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_float_to_q15.c  
00009 *  
00010 * Description:  Processing function for the Conversion from float to Q15  
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  * @addtogroup float_to_x  
00035  * @{  
00036  */ 
00037  
00038 /**  
00039  * @brief Converts the elements of the floating-point vector to Q15 vector.  
00040  * @param[in]       *pSrc points to the floating-point input vector  
00041  * @param[out]      *pDst points to the Q15 output vector 
00042  * @param[in]       blockSize length of the input vector  
00043  * @return none.  
00044  *  
00045  * \par Description:  
00046  * \par 
00047  * The equation used for the conversion process is:  
00048  * <pre>  
00049  *  pDst[n] = (q15_t)(pSrc[n] * 32768);   0 <= n < blockSize.  
00050  * </pre>  
00051  * \par Scaling and Overflow Behavior:  
00052  * \par  
00053  * The function uses saturating arithmetic.  
00054  * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.  
00055  * \note 
00056  * In order to apply rounding, the library should be rebuilt with the ROUNDING macro   
00057  * defined in the preprocessor section of project options.   
00058  *  
00059  */ 
00060  
00061  
00062 void arm_float_to_q15( 
00063   float32_t * pSrc, 
00064   q15_t * pDst, 
00065   uint32_t blockSize) 
00066 { 
00067   float32_t *pIn = pSrc;                         /* Src pointer */ 
00068   uint32_t blkCnt;                               /* loop counter */ 
00069  
00070 #ifdef ARM_MATH_ROUNDING 
00071  
00072   float32_t in; 
00073  
00074 #endif 
00075  
00076   /*loop Unrolling */ 
00077   blkCnt = blockSize >> 2u; 
00078  
00079   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00080    ** a second loop below computes the remaining 1 to 3 samples. */ 
00081   while(blkCnt > 0u) 
00082   { 
00083  
00084 #ifdef ARM_MATH_ROUNDING 
00085     /* C = A * 32768 */ 
00086     /* convert from float to q15 and then store the results in the destination buffer */ 
00087     in = *pIn++; 
00088     in = (in * 32768.0f); 
00089     in += in > 0 ? 0.5 : -0.5; 
00090     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16)); 
00091  
00092     in = *pIn++; 
00093     in = (in * 32768.0f); 
00094     in += in > 0 ? 0.5 : -0.5; 
00095     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16)); 
00096  
00097     in = *pIn++; 
00098     in = (in * 32768.0f); 
00099     in += in > 0 ? 0.5 : -0.5; 
00100     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16)); 
00101  
00102     in = *pIn++; 
00103     in = (in * 32768.0f); 
00104     in += in > 0 ? 0.5 : -0.5; 
00105     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16)); 
00106  
00107 #else 
00108  
00109     /* C = A * 32768 */ 
00110     /* convert from float to q15 and then store the results in the destination buffer */ 
00111     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16); 
00112     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16); 
00113     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16); 
00114     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16); 
00115  
00116 #endif 
00117  
00118     /* Decrement the loop counter */ 
00119     blkCnt--; 
00120   } 
00121  
00122   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00123    ** No loop unrolling is used. */ 
00124   blkCnt = blockSize % 0x4u; 
00125  
00126   while(blkCnt > 0u) 
00127   { 
00128  
00129 #ifdef ARM_MATH_ROUNDING 
00130     /* C = A * 32768 */ 
00131     /* convert from float to q15 and then store the results in the destination buffer */ 
00132     in = *pIn++; 
00133     in = (in * 32768LL); 
00134     in += in > 0 ? 0.5 : -0.5; 
00135     *pDst++ = (q15_t) (__SSAT((q31_t) (in), 16)); 
00136  
00137 #else 
00138  
00139     /* C = A * 32768 */ 
00140     /* convert from float to q15 and then store the results in the destination buffer */ 
00141     *pDst++ = (q15_t) __SSAT((q31_t) (*pIn++ * 32768.0f), 16); 
00142  
00143 #endif 
00144  
00145     /* Decrement the loop counter */ 
00146     blkCnt--; 
00147   } 
00148 } 
00149  
00150 /**  
00151  * @} end of float_to_x group  
00152  */