arm_float_to_q7.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_q7.c  
00009 *  
00010 * Description:  Processing function for the Conversion from float to Q7  
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 Q7 vector.  
00040  * @param[in]       *pSrc points to the floating-point input vector  
00041  * @param[out]      *pDst points to the Q7 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] = (q7_t)(pSrc[n] * 128);   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 Q7 range [0x80 0x7F] 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 void arm_float_to_q7( 
00062   float32_t * pSrc, 
00063   q7_t * pDst, 
00064   uint32_t blockSize) 
00065 { 
00066   float32_t *pIn = pSrc;                         /* Src pointer */ 
00067   uint32_t blkCnt;                               /* loop counter */ 
00068  
00069 #ifdef ARM_MATH_ROUNDING 
00070  
00071   float32_t in; 
00072  
00073 #endif 
00074  
00075   /*loop Unrolling */ 
00076   blkCnt = blockSize >> 2u; 
00077  
00078   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00079    ** a second loop below computes the remaining 1 to 3 samples. */ 
00080   while(blkCnt > 0u) 
00081   { 
00082 #ifdef ARM_MATH_ROUNDING 
00083     /* C = A * 128 */ 
00084     /* convert from float to q7 and then store the results in the destination buffer */ 
00085     in = *pIn++; 
00086     in = (in * 128); 
00087     in += in > 0 ? 0.5 : -0.5; 
00088     *pDst++ = (q7_t) (__SSAT((q15_t) (in), 8)); 
00089  
00090     in = *pIn++; 
00091     in = (in * 128); 
00092     in += in > 0 ? 0.5 : -0.5; 
00093     *pDst++ = (q7_t) (__SSAT((q15_t) (in), 8)); 
00094  
00095     in = *pIn++; 
00096     in = (in * 128); 
00097     in += in > 0 ? 0.5 : -0.5; 
00098     *pDst++ = (q7_t) (__SSAT((q15_t) (in), 8)); 
00099  
00100     in = *pIn++; 
00101     in = (in * 128); 
00102     in += in > 0 ? 0.5 : -0.5; 
00103     *pDst++ = (q7_t) (__SSAT((q15_t) (in), 8)); 
00104  
00105 #else 
00106  
00107     /* C = A * 128 */ 
00108     /* convert from float to q7 and then store the results in the destination buffer */ 
00109     *pDst++ = __SSAT((q31_t) (*pIn++ * 128.0f), 8); 
00110     *pDst++ = __SSAT((q31_t) (*pIn++ * 128.0f), 8); 
00111     *pDst++ = __SSAT((q31_t) (*pIn++ * 128.0f), 8); 
00112     *pDst++ = __SSAT((q31_t) (*pIn++ * 128.0f), 8); 
00113  
00114 #endif 
00115  
00116     /* Decrement the loop counter */ 
00117     blkCnt--; 
00118   } 
00119  
00120   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00121    ** No loop unrolling is used. */ 
00122   blkCnt = blockSize % 0x4u; 
00123  
00124   while(blkCnt > 0u) 
00125   { 
00126 #ifdef ARM_MATH_ROUNDING 
00127     /* C = A * 128 */ 
00128     /* convert from float to q7 and then store the results in the destination buffer */ 
00129     in = *pIn++; 
00130     in = (in * 128); 
00131     in += in > 0 ? 0.5 : -0.5; 
00132     *pDst++ = (q7_t) (__SSAT((q15_t) (in), 8)); 
00133  
00134 #else 
00135  
00136     /* C = A * 128 */ 
00137     /* convert from float to q7 and then store the results in the destination buffer */ 
00138     *pDst++ = __SSAT((q31_t) (*pIn++ * 128.0f), 8); 
00139  
00140 #endif 
00141  
00142     /* Decrement the loop counter */ 
00143     blkCnt--; 
00144   } 
00145 } 
00146  
00147 /**  
00148  * @} end of float_to_x group  
00149  */