Laxmi Kant Tiwari
CMSIS DSP Lib
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Diff: cmsis_dsp/TransformFunctions/arm_rfft_f32.c
- Revision:
- 1:fdd22bb7aa52
- Child:
- 2:da51fb522205
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/TransformFunctions/arm_rfft_f32.c Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,382 @@
+/* ----------------------------------------------------------------------
+* Copyright (C) 2010 ARM Limited. All rights reserved.
+*
+* $Date: 15. February 2012
+* $Revision: V1.1.0
+*
+* Project: CMSIS DSP Library
+* Title: arm_rfft_f32.c
+*
+* Description: RFFT & RIFFT Floating point process function
+*
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*
+* Version 1.1.0 2012/02/15
+* Updated with more optimizations, bug fixes and minor API changes.
+*
+* Version 1.0.10 2011/7/15
+* Big Endian support added and Merged M0 and M3/M4 Source code.
+*
+* Version 1.0.3 2010/11/29
+* Re-organized the CMSIS folders and updated documentation.
+*
+* Version 1.0.2 2010/11/11
+* Documentation updated.
+*
+* Version 1.0.1 2010/10/05
+* Production release and review comments incorporated.
+*
+* Version 1.0.0 2010/09/20
+* Production release and review comments incorporated.
+*
+* Version 0.0.7 2010/06/10
+* Misra-C changes done
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**
+ * @ingroup groupTransforms
+ */
+
+/**
+ * @defgroup RFFT_RIFFT Real FFT Functions
+ *
+ * \par
+ * Complex FFT/IFFT typically assumes complex input and output. However many applications use real valued data in time domain.
+ * Real FFT/IFFT efficiently process real valued sequences with the advantage of requirement of low memory and with less complexity.
+ *
+ * \par
+ * This set of functions implements Real Fast Fourier Transforms(RFFT) and Real Inverse Fast Fourier Transform(RIFFT)
+ * for Q15, Q31, and floating-point data types.
+ *
+ *
+ * \par Algorithm:
+ *
+ * <b>Real Fast Fourier Transform:</b>
+ * \par
+ * Real FFT of N-point is calculated using CFFT of N/2-point and Split RFFT process as shown below figure.
+ * \par
+ * \image html RFFT.gif "Real Fast Fourier Transform"
+ * \par
+ * The RFFT functions operate on blocks of input and output data and each call to the function processes
+ * <code>fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>fftLenR</code> values.
+ * <code>pDst</code> points to output array containing <code>2*fftLenR</code> values. \n
+ * Input for real FFT is in the order of
+ * <pre>{real[0], real[1], real[2], real[3], ..}</pre>
+ * Output for real FFT is complex and are in the order of
+ * <pre>{real(0), imag(0), real(1), imag(1), ...}</pre>
+ *
+ * <b>Real Inverse Fast Fourier Transform:</b>
+ * \par
+ * Real IFFT of N-point is calculated using Split RIFFT process and CFFT of N/2-point as shown below figure.
+ * \par
+ * \image html RIFFT.gif "Real Inverse Fast Fourier Transform"
+ * \par
+ * The RIFFT functions operate on blocks of input and output data and each call to the function processes
+ * <code>2*fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>2*fftLenR</code> values.
+ * <code>pDst</code> points to output array containing <code>fftLenR</code> values. \n
+ * Input for real IFFT is complex and are in the order of
+ * <pre>{real(0), imag(0), real(1), imag(1), ...}</pre>
+ * Output for real IFFT is real and in the order of
+ * <pre>{real[0], real[1], real[2], real[3], ..}</pre>
+ *
+ * \par Lengths supported by the transform:
+ * \par
+ * Real FFT/IFFT supports the lengths [128, 512, 2048], as it internally uses CFFT/CIFFT.
+ *
+ * \par Instance Structure
+ * A separate instance structure must be defined for each Instance but the twiddle factors can be reused.
+ * There are separate instance structure declarations for each of the 3 supported data types.
+ *
+ * \par Initialization Functions
+ * There is also an associated initialization function for each data type.
+ * The initialization function performs the following operations:
+ * - Sets the values of the internal structure fields.
+ * - Initializes twiddle factor tables.
+ * - Initializes CFFT data structure fields.
+ * \par
+ * Use of the initialization function is optional.
+ * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
+ * To place an instance structure into a const data section, the instance structure must be manually initialized.
+ * Manually initialize the instance structure as follows:
+ * <pre>
+ *arm_rfft_instance_f32 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
+ *arm_rfft_instance_q31 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
+ *arm_rfft_instance_q15 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft};
+ * </pre>
+ * where <code>fftLenReal</code> length of RFFT/RIFFT; <code>fftLenBy2</code> length of CFFT/CIFFT.
+ * <code>ifftFlagR</code> Flag for selection of RFFT or RIFFT(Set ifftFlagR to calculate RIFFT otherwise calculates RFFT);
+ * <code>bitReverseFlagR</code> Flag for selection of output order(Set bitReverseFlagR to output in normal order otherwise output in bit reversed order);
+ * <code>twidCoefRModifier</code> modifier for twiddle factor table which supports 128, 512, 2048 RFFT lengths with same table;
+ * <code>pTwiddleAReal</code>points to A array of twiddle coefficients; <code>pTwiddleBReal</code>points to B array of twiddle coefficients;
+ * <code>pCfft</code> points to the CFFT Instance structure. The CFFT structure also needs to be initialized, refer to arm_cfft_radix4_f32() for details regarding
+ * static initialization of cfft structure.
+ *
+ * \par Fixed-Point Behavior
+ * Care must be taken when using the fixed-point versions of the RFFT/RIFFT function.
+ * Refer to the function specific documentation below for usage guidelines.
+ */
+
+/*--------------------------------------------------------------------
+ * Internal functions prototypes
+ *--------------------------------------------------------------------*/
+
+void arm_split_rfft_f32(
+ float32_t * pSrc,
+ uint32_t fftLen,
+ float32_t * pATable,
+ float32_t * pBTable,
+ float32_t * pDst,
+ uint32_t modifier);
+void arm_split_rifft_f32(
+ float32_t * pSrc,
+ uint32_t fftLen,
+ float32_t * pATable,
+ float32_t * pBTable,
+ float32_t * pDst,
+ uint32_t modifier);
+
+/**
+ * @addtogroup RFFT_RIFFT
+ * @{
+ */
+
+/**
+ * @brief Processing function for the floating-point RFFT/RIFFT.
+ * @param[in] *S points to an instance of the floating-point RFFT/RIFFT structure.
+ * @param[in] *pSrc points to the input buffer.
+ * @param[out] *pDst points to the output buffer.
+ * @return none.
+ */
+
+void arm_rfft_f32(
+ const arm_rfft_instance_f32 * S,
+ float32_t * pSrc,
+ float32_t * pDst)
+{
+ const arm_cfft_radix4_instance_f32 *S_CFFT = S->pCfft;
+
+
+ /* Calculation of Real IFFT of input */
+ if(S->ifftFlagR == 1u)
+ {
+ /* Real IFFT core process */
+ arm_split_rifft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
+ S->pTwiddleBReal, pDst, S->twidCoefRModifier);
+
+
+ /* Complex radix-4 IFFT process */
+ arm_radix4_butterfly_inverse_f32(pDst, S_CFFT->fftLen,
+ S_CFFT->pTwiddle,
+ S_CFFT->twidCoefModifier,
+ S_CFFT->onebyfftLen);
+
+ /* Bit reversal process */
+ if(S->bitReverseFlagR == 1u)
+ {
+ arm_bitreversal_f32(pDst, S_CFFT->fftLen,
+ S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
+ }
+ }
+ else
+ {
+
+ /* Calculation of RFFT of input */
+
+ /* Complex radix-4 FFT process */
+ arm_radix4_butterfly_f32(pSrc, S_CFFT->fftLen,
+ S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);
+
+ /* Bit reversal process */
+ if(S->bitReverseFlagR == 1u)
+ {
+ arm_bitreversal_f32(pSrc, S_CFFT->fftLen,
+ S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
+ }
+
+
+ /* Real FFT core process */
+ arm_split_rfft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
+ S->pTwiddleBReal, pDst, S->twidCoefRModifier);
+ }
+
+}
+
+/**
+ * @} end of RFFT_RIFFT group
+ */
+
+/**
+ * @brief Core Real FFT process
+ * @param[in] *pSrc points to the input buffer.
+ * @param[in] fftLen length of FFT.
+ * @param[in] *pATable points to the twiddle Coef A buffer.
+ * @param[in] *pBTable points to the twiddle Coef B buffer.
+ * @param[out] *pDst points to the output buffer.
+ * @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
+ * @return none.
+ */
+
+void arm_split_rfft_f32(
+ float32_t * pSrc,
+ uint32_t fftLen,
+ float32_t * pATable,
+ float32_t * pBTable,
+ float32_t * pDst,
+ uint32_t modifier)
+{
+ uint32_t i; /* Loop Counter */
+ float32_t outR, outI; /* Temporary variables for output */
+ float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
+ float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
+ float32_t *pDst1 = &pDst[2], *pDst2 = &pDst[(4u * fftLen) - 1u]; /* temp pointers for output buffer */
+ float32_t *pSrc1 = &pSrc[2], *pSrc2 = &pSrc[(2u * fftLen) - 1u]; /* temp pointers for input buffer */
+
+ /* Init coefficient pointers */
+ pCoefA = &pATable[modifier * 2u];
+ pCoefB = &pBTable[modifier * 2u];
+
+ i = fftLen - 1u;
+
+ while(i > 0u)
+ {
+ /*
+ outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
+ + pSrc[2 * n - 2 * i] * pBTable[2 * i] +
+ pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
+ */
+
+ /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
+ pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
+ pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */
+
+ /* read pATable[2 * i] */
+ CoefA1 = *pCoefA++;
+ /* pATable[2 * i + 1] */
+ CoefA2 = *pCoefA;
+
+ /* pSrc[2 * i] * pATable[2 * i] */
+ outR = *pSrc1 * CoefA1;
+ /* pSrc[2 * i] * CoefA2 */
+ outI = *pSrc1++ * CoefA2;
+
+ /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
+ outR -= (*pSrc1 + *pSrc2) * CoefA2;
+ /* pSrc[2 * i + 1] * CoefA1 */
+ outI += *pSrc1++ * CoefA1;
+
+ CoefB1 = *pCoefB;
+
+ /* pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
+ outI -= *pSrc2-- * CoefB1;
+ /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
+ outI -= *pSrc2 * CoefA2;
+
+ /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
+ outR += *pSrc2-- * CoefB1;
+
+ /* write output */
+ *pDst1++ = outR;
+ *pDst1++ = outI;
+
+ /* write complex conjugate output */
+ *pDst2-- = -outI;
+ *pDst2-- = outR;
+
+ /* update coefficient pointer */
+ pCoefB = pCoefB + (modifier * 2u);
+ pCoefA = pCoefA + ((modifier * 2u) - 1u);
+
+ i--;
+
+ }
+
+ pDst[2u * fftLen] = pSrc[0] - pSrc[1];
+ pDst[(2u * fftLen) + 1u] = 0.0f;
+
+ pDst[0] = pSrc[0] + pSrc[1];
+ pDst[1] = 0.0f;
+
+}
+
+
+/**
+ * @brief Core Real IFFT process
+ * @param[in] *pSrc points to the input buffer.
+ * @param[in] fftLen length of FFT.
+ * @param[in] *pATable points to the twiddle Coef A buffer.
+ * @param[in] *pBTable points to the twiddle Coef B buffer.
+ * @param[out] *pDst points to the output buffer.
+ * @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
+ * @return none.
+ */
+
+void arm_split_rifft_f32(
+ float32_t * pSrc,
+ uint32_t fftLen,
+ float32_t * pATable,
+ float32_t * pBTable,
+ float32_t * pDst,
+ uint32_t modifier)
+{
+ float32_t outR, outI; /* Temporary variables for output */
+ float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
+ float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
+ float32_t *pSrc1 = &pSrc[0], *pSrc2 = &pSrc[(2u * fftLen) + 1u];
+
+ pCoefA = &pATable[0];
+ pCoefB = &pBTable[0];
+
+ while(fftLen > 0u)
+ {
+ /*
+ outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
+ pIn[2 * n - 2 * i] * pBTable[2 * i] -
+ pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
+
+ outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
+ pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
+ pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
+
+ */
+
+ CoefA1 = *pCoefA++;
+ CoefA2 = *pCoefA;
+
+ /* outR = (pSrc[2 * i] * CoefA1 */
+ outR = *pSrc1 * CoefA1;
+
+ /* - pSrc[2 * i] * CoefA2 */
+ outI = -(*pSrc1++) * CoefA2;
+
+ /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
+ outR += (*pSrc1 + *pSrc2) * CoefA2;
+
+ /* pSrc[2 * i + 1] * CoefA1 */
+ outI += (*pSrc1++) * CoefA1;
+
+ CoefB1 = *pCoefB;
+
+ /* - pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
+ outI -= *pSrc2-- * CoefB1;
+
+ /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
+ outR += *pSrc2 * CoefB1;
+
+ /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
+ outI += *pSrc2-- * CoefA2;
+
+ /* write output */
+ *pDst++ = outR;
+ *pDst++ = outI;
+
+ /* update coefficient pointer */
+ pCoefB = pCoefB + (modifier * 2u);
+ pCoefA = pCoefA + ((modifier * 2u) - 1u);
+
+ /* Decrement loop count */
+ fftLen--;
+ }
+
+}