arm_cfft_radix2_init_q15.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_cfft_radix2_init_q15.c    
00009 *    
00010 * Description:  Radix-2 Decimation in Frequency Q15 FFT & IFFT initialization function    
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 #include "arm_common_tables.h"
00043 
00044 /**    
00045  * @ingroup groupTransforms    
00046  */
00047 
00048 
00049 /**    
00050  * @addtogroup ComplexFFT    
00051  * @{    
00052  */
00053 
00054 /**   
00055 * @brief Initialization function for the Q15 CFFT/CIFFT.   
00056 * @param[in,out] *S             points to an instance of the Q15 CFFT/CIFFT structure.   
00057 * @param[in]     fftLen         length of the FFT.   
00058 * @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.  
00059 * @param[in]     bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.  
00060 * @return        The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLen</code> is not a supported value.  
00061 *   
00062 * \par Description:  
00063 * \par   
00064 * The parameter <code>ifftFlag</code> controls whether a forward or inverse transform is computed.   
00065 * Set(=1) ifftFlag for calculation of CIFFT otherwise  CFFT is calculated  
00066 * \par   
00067 * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.   
00068 * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.   
00069 * \par   
00070 * The parameter <code>fftLen</code> Specifies length of CFFT/CIFFT process. Supported FFT Lengths are 16, 64, 256, 1024.   
00071 * \par   
00072 * This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.   
00073 */
00074 
00075 arm_status arm_cfft_radix2_init_q15(
00076   arm_cfft_radix2_instance_q15 * S,
00077   uint16_t fftLen,
00078   uint8_t ifftFlag,
00079   uint8_t bitReverseFlag)
00080 {
00081   /*  Initialise the default arm status */
00082   arm_status status = ARM_MATH_SUCCESS;
00083 
00084   /*  Initialise the FFT length */
00085   S->fftLen = fftLen;
00086 
00087   /*  Initialise the Twiddle coefficient pointer */
00088   S->pTwiddle = (q15_t *) twiddleCoefQ15 ;
00089   /*  Initialise the Flag for selection of CFFT or CIFFT */
00090   S->ifftFlag = ifftFlag;
00091   /*  Initialise the Flag for calculation Bit reversal or not */
00092   S->bitReverseFlag = bitReverseFlag;
00093 
00094   /*  Initializations of structure parameters depending on the FFT length */
00095   switch (S->fftLen)
00096   {
00097   case 4096u:
00098     /*  Initializations of structure parameters for 4096 point FFT */
00099 
00100     /*  Initialise the twiddle coef modifier value */
00101     S->twidCoefModifier = 1u;
00102     /*  Initialise the bit reversal table modifier */
00103     S->bitRevFactor = 1u;
00104     /*  Initialise the bit reversal table pointer */
00105     S->pBitRevTable = (uint16_t *) armBitRevTable ;
00106 
00107     break;
00108 
00109   case 2048u:
00110     /*  Initializations of structure parameters for 2048 point FFT */
00111 
00112     /*  Initialise the twiddle coef modifier value */
00113     S->twidCoefModifier = 2u;
00114     /*  Initialise the bit reversal table modifier */
00115     S->bitRevFactor = 2u;
00116     /*  Initialise the bit reversal table pointer */
00117     S->pBitRevTable = (uint16_t *) & armBitRevTable [1];
00118 
00119     break;
00120 
00121   case 1024u:
00122     /*  Initializations of structure parameters for 1024 point FFT */
00123     S->twidCoefModifier = 4u;
00124     S->bitRevFactor = 4u;
00125     S->pBitRevTable = (uint16_t *) & armBitRevTable [3];
00126 
00127     break;
00128 
00129   case 512u:
00130     /*  Initializations of structure parameters for 512 point FFT */
00131     S->twidCoefModifier = 8u;
00132     S->bitRevFactor = 8u;
00133     S->pBitRevTable = (uint16_t *) & armBitRevTable [7];
00134 
00135     break;
00136 
00137   case 256u:
00138     /*  Initializations of structure parameters for 256 point FFT */
00139     S->twidCoefModifier = 16u;
00140     S->bitRevFactor = 16u;
00141     S->pBitRevTable = (uint16_t *) & armBitRevTable [15];
00142 
00143     break;
00144 
00145   case 128u:
00146     /*  Initializations of structure parameters for 128 point FFT */
00147     S->twidCoefModifier = 32u;
00148     S->bitRevFactor = 32u;
00149     S->pBitRevTable = (uint16_t *) & armBitRevTable [31];
00150 
00151     break;
00152 
00153   case 64u:
00154     /*  Initializations of structure parameters for 64 point FFT */
00155     S->twidCoefModifier = 64u;
00156     S->bitRevFactor = 64u;
00157     S->pBitRevTable = (uint16_t *) & armBitRevTable [63];
00158 
00159     break;
00160 
00161   case 32u:
00162     /*  Initializations of structure parameters for 32 point FFT */
00163     S->twidCoefModifier = 128u;
00164     S->bitRevFactor = 128u;
00165     S->pBitRevTable = (uint16_t *) & armBitRevTable [127];
00166 
00167     break;
00168 
00169   case 16u:
00170     /*  Initializations of structure parameters for 16 point FFT */
00171     S->twidCoefModifier = 256u;
00172     S->bitRevFactor = 256u;
00173     S->pBitRevTable = (uint16_t *) & armBitRevTable [255];
00174 
00175     break;
00176 
00177   default:
00178     /*  Reporting argument error if fftSize is not valid value */
00179     status = ARM_MATH_ARGUMENT_ERROR;
00180     break;
00181   }
00182 
00183   return (status);
00184 }
00185 
00186 /**    
00187  * @} end of ComplexFFT group    
00188  */