Diff: cmsis_dsp/FilteringFunctions/arm_fir_decimate_f32.c

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1:fdd22bb7aa52

Child:

2:da51fb522205

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/FilteringFunctions/arm_fir_decimate_f32.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,518 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010 ARM Limited. All rights reserved.    
+*    
+* $Date:        15. February 2012  
+* $Revision:     V1.1.0  
+*    
+* Project:         CMSIS DSP Library    
+* Title:        arm_fir_decimate_f32.c    
+*    
+* Description:    FIR decimation for floating-point sequences.    
+*    
+* 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 groupFilters    
+ */
+
+/**    
+ * @defgroup FIR_decimate Finite Impulse Response (FIR) Decimator    
+ *    
+ * These functions combine an FIR filter together with a decimator.    
+ * They are used in multirate systems for reducing the sample rate of a signal without introducing aliasing distortion.    
+ * Conceptually, the functions are equivalent to the block diagram below:    
+ * \image html FIRDecimator.gif "Components included in the FIR Decimator functions"    
+ * When decimating by a factor of <code>M</code>, the signal should be prefiltered by a lowpass filter with a normalized    
+ * cutoff frequency of <code>1/M</code> in order to prevent aliasing distortion.    
+ * The user of the function is responsible for providing the filter coefficients.    
+ *    
+ * The FIR decimator functions provided in the CMSIS DSP Library combine the FIR filter and the decimator in an efficient manner.    
+ * Instead of calculating all of the FIR filter outputs and discarding <code>M-1</code> out of every <code>M</code>, only the    
+ * samples output by the decimator are computed.    
+ * The functions operate on blocks of input and output data.    
+ * <code>pSrc</code> points to an array of <code>blockSize</code> input values and    
+ * <code>pDst</code> points to an array of <code>blockSize/M</code> output values.    
+ * In order to have an integer number of output samples <code>blockSize</code>    
+ * must always be a multiple of the decimation factor <code>M</code>.    
+ *    
+ * The library provides separate functions for Q15, Q31 and floating-point data types.    
+ *    
+ * \par Algorithm:    
+ * The FIR portion of the algorithm uses the standard form filter:    
+ * <pre>    
+ *    y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1]    
+ * </pre>    
+ * where, <code>b[n]</code> are the filter coefficients.    
+ * \par   
+ * The <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>.    
+ * Coefficients are stored in time reversed order.    
+ * \par    
+ * <pre>    
+ *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}    
+ * </pre>    
+ * \par    
+ * <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>.    
+ * Samples in the state buffer are stored in the order:    
+ * \par    
+ * <pre>    
+ *    {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]}    
+ * </pre>    
+ * The state variables are updated after each block of data is processed, the coefficients are untouched.    
+ *    
+ * \par Instance Structure    
+ * The coefficients and state variables for a filter are stored together in an instance data structure.    
+ * A separate instance structure must be defined for each filter.    
+ * Coefficient arrays may be shared among several instances while state variable array should be allocated separately.    
+ * 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.    
+ * - Zeros out the values in the state buffer.    
+ * - Checks to make sure that the size of the input is a multiple of the decimation factor.    
+ *    
+ * \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.    
+ * The code below statically initializes each of the 3 different data type filter instance structures    
+ * <pre>    
+ *arm_fir_decimate_instance_f32 S = {M, numTaps, pCoeffs, pState};    
+ *arm_fir_decimate_instance_q31 S = {M, numTaps, pCoeffs, pState};    
+ *arm_fir_decimate_instance_q15 S = {M, numTaps, pCoeffs, pState};    
+ * </pre>    
+ * where <code>M</code> is the decimation factor; <code>numTaps</code> is the number of filter coefficients in the filter;    
+ * <code>pCoeffs</code> is the address of the coefficient buffer;    
+ * <code>pState</code> is the address of the state buffer.    
+ * Be sure to set the values in the state buffer to zeros when doing static initialization.    
+ *    
+ * \par Fixed-Point Behavior    
+ * Care must be taken when using the fixed-point versions of the FIR decimate filter functions.    
+ * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.    
+ * Refer to the function specific documentation below for usage guidelines.    
+ */
+
+/**    
+ * @addtogroup FIR_decimate    
+ * @{    
+ */
+
+  /**    
+   * @brief Processing function for the floating-point FIR decimator.    
+   * @param[in] *S        points to an instance of the floating-point FIR decimator structure.    
+   * @param[in] *pSrc     points to the block of input data.    
+   * @param[out] *pDst    points to the block of output data.    
+   * @param[in] blockSize number of input samples to process per call.    
+   * @return none.    
+   */
+
+void arm_fir_decimate_f32(
+  const arm_fir_decimate_instance_f32 * S,
+  float32_t * pSrc,
+  float32_t * pDst,
+  uint32_t blockSize)
+{
+  float32_t *pState = S->pState;                 /* State pointer */
+  float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
+  float32_t *pStateCurnt;                        /* Points to the current sample of the state */
+  float32_t *px, *pb;                            /* Temporary pointers for state and coefficient buffers */
+  float32_t sum0;                                /* Accumulator */
+  float32_t x0, c0;                              /* Temporary variables to hold state and coefficient values */
+  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */
+  uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M;  /* Loop counters */
+
+#ifndef ARM_MATH_CM0
+
+  uint32_t blkCntN4;
+  float32_t *px0, *px1, *px2, *px3;
+  float32_t acc0, acc1, acc2, acc3;
+  float32_t x1, x2, x3;
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  /* S->pState buffer contains previous frame (numTaps - 1) samples */
+  /* pStateCurnt points to the location where the new input data should be written */
+  pStateCurnt = S->pState + (numTaps - 1u);
+
+  /* Total number of output samples to be computed */
+  blkCnt = outBlockSize / 4;
+  blkCntN4 = outBlockSize - (4 * blkCnt);
+
+  while(blkCnt > 0u)
+  {
+    /* Copy 4 * decimation factor number of new input samples into the state buffer */
+    i = 4 * S->M;
+
+    do
+    {
+      *pStateCurnt++ = *pSrc++;
+
+    } while(--i);
+
+    /* Set accumulators to zero */
+    acc0 = 0.0f;
+    acc1 = 0.0f;
+    acc2 = 0.0f;
+    acc3 = 0.0f;
+
+    /* Initialize state pointer for all the samples */
+    px0 = pState;
+    px1 = pState + S->M;
+    px2 = pState + 2 * S->M;
+    px3 = pState + 3 * S->M;
+
+    /* Initialize coeff pointer */
+    pb = pCoeffs;
+
+    /* Loop unrolling.  Process 4 taps at a time. */
+    tapCnt = numTaps >> 2;
+
+    /* Loop over the number of taps.  Unroll by a factor of 4.       
+     ** Repeat until we've computed numTaps-4 coefficients. */
+
+    while(tapCnt > 0u)
+    {
+      /* Read the b[numTaps-1] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-1] sample for acc0 */
+      x0 = *(px0++);
+      /* Read x[n-numTaps-1] sample for acc1 */
+      x1 = *(px1++);
+      /* Read x[n-numTaps-1] sample for acc2 */
+      x2 = *(px2++);
+      /* Read x[n-numTaps-1] sample for acc3 */
+      x3 = *(px3++);
+
+      /* Perform the multiply-accumulate */
+      acc0 += x0 * c0;
+      acc1 += x1 * c0;
+      acc2 += x2 * c0;
+      acc3 += x3 * c0;
+
+      /* Read the b[numTaps-2] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-2] sample for acc0, acc1, acc2, acc3 */
+      x0 = *(px0++);
+      x1 = *(px1++);
+      x2 = *(px2++);
+      x3 = *(px3++);
+
+      /* Perform the multiply-accumulate */
+      acc0 += x0 * c0;
+      acc1 += x1 * c0;
+      acc2 += x2 * c0;
+      acc3 += x3 * c0;
+
+      /* Read the b[numTaps-3] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-3] sample acc0, acc1, acc2, acc3 */
+      x0 = *(px0++);
+      x1 = *(px1++);
+      x2 = *(px2++);
+      x3 = *(px3++);
+
+      /* Perform the multiply-accumulate */
+      acc0 += x0 * c0;
+      acc1 += x1 * c0;
+      acc2 += x2 * c0;
+      acc3 += x3 * c0;
+
+      /* Read the b[numTaps-4] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-4] sample acc0, acc1, acc2, acc3 */
+      x0 = *(px0++);
+      x1 = *(px1++);
+      x2 = *(px2++);
+      x3 = *(px3++);
+
+      /* Perform the multiply-accumulate */
+      acc0 += x0 * c0;
+      acc1 += x1 * c0;
+      acc2 += x2 * c0;
+      acc3 += x3 * c0;
+
+      /* Decrement the loop counter */
+      tapCnt--;
+    }
+
+    /* If the filter length is not a multiple of 4, compute the remaining filter taps */
+    tapCnt = numTaps % 0x4u;
+
+    while(tapCnt > 0u)
+    {
+      /* Read coefficients */
+      c0 = *(pb++);
+
+      /* Fetch  state variables for acc0, acc1, acc2, acc3 */
+      x0 = *(px0++);
+      x1 = *(px1++);
+      x2 = *(px2++);
+      x3 = *(px3++);
+
+      /* Perform the multiply-accumulate */
+      acc0 += x0 * c0;
+      acc1 += x1 * c0;
+      acc2 += x2 * c0;
+      acc3 += x3 * c0;
+
+      /* Decrement the loop counter */
+      tapCnt--;
+    }
+
+    /* Advance the state pointer by the decimation factor       
+     * to process the next group of decimation factor number samples */
+    pState = pState + 4 * S->M;
+
+    /* The result is in the accumulator, store in the destination buffer. */
+    *pDst++ = acc0;
+    *pDst++ = acc1;
+    *pDst++ = acc2;
+    *pDst++ = acc3;
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  while(blkCntN4 > 0u)
+  {
+    /* Copy decimation factor number of new input samples into the state buffer */
+    i = S->M;
+
+    do
+    {
+      *pStateCurnt++ = *pSrc++;
+
+    } while(--i);
+
+    /* Set accumulator to zero */
+    sum0 = 0.0f;
+
+    /* Initialize state pointer */
+    px = pState;
+
+    /* Initialize coeff pointer */
+    pb = pCoeffs;
+
+    /* Loop unrolling.  Process 4 taps at a time. */
+    tapCnt = numTaps >> 2;
+
+    /* Loop over the number of taps.  Unroll by a factor of 4.       
+     ** Repeat until we've computed numTaps-4 coefficients. */
+    while(tapCnt > 0u)
+    {
+      /* Read the b[numTaps-1] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-1] sample */
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Read the b[numTaps-2] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-2] sample */
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Read the b[numTaps-3] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-3] sample */
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Read the b[numTaps-4] coefficient */
+      c0 = *(pb++);
+
+      /* Read x[n-numTaps-4] sample */
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Decrement the loop counter */
+      tapCnt--;
+    }
+
+    /* If the filter length is not a multiple of 4, compute the remaining filter taps */
+    tapCnt = numTaps % 0x4u;
+
+    while(tapCnt > 0u)
+    {
+      /* Read coefficients */
+      c0 = *(pb++);
+
+      /* Fetch 1 state variable */
+      x0 = *(px++);
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Decrement the loop counter */
+      tapCnt--;
+    }
+
+    /* Advance the state pointer by the decimation factor       
+     * to process the next group of decimation factor number samples */
+    pState = pState + S->M;
+
+    /* The result is in the accumulator, store in the destination buffer. */
+    *pDst++ = sum0;
+
+    /* Decrement the loop counter */
+    blkCntN4--;
+  }
+
+  /* Processing is complete.    
+   ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.    
+   ** This prepares the state buffer for the next function call. */
+
+  /* Points to the start of the state buffer */
+  pStateCurnt = S->pState;
+
+  i = (numTaps - 1u) >> 2;
+
+  /* copy data */
+  while(i > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    i--;
+  }
+
+  i = (numTaps - 1u) % 0x04u;
+
+  /* copy data */
+  while(i > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    i--;
+  }
+
+#else
+
+/* Run the below code for Cortex-M0 */
+
+  /* S->pState buffer contains previous frame (numTaps - 1) samples */
+  /* pStateCurnt points to the location where the new input data should be written */
+  pStateCurnt = S->pState + (numTaps - 1u);
+
+  /* Total number of output samples to be computed */
+  blkCnt = outBlockSize;
+
+  while(blkCnt > 0u)
+  {
+    /* Copy decimation factor number of new input samples into the state buffer */
+    i = S->M;
+
+    do
+    {
+      *pStateCurnt++ = *pSrc++;
+
+    } while(--i);
+
+    /* Set accumulator to zero */
+    sum0 = 0.0f;
+
+    /* Initialize state pointer */
+    px = pState;
+
+    /* Initialize coeff pointer */
+    pb = pCoeffs;
+
+    tapCnt = numTaps;
+
+    while(tapCnt > 0u)
+    {
+      /* Read coefficients */
+      c0 = *pb++;
+
+      /* Fetch 1 state variable */
+      x0 = *px++;
+
+      /* Perform the multiply-accumulate */
+      sum0 += x0 * c0;
+
+      /* Decrement the loop counter */
+      tapCnt--;
+    }
+
+    /* Advance the state pointer by the decimation factor           
+     * to process the next group of decimation factor number samples */
+    pState = pState + S->M;
+
+    /* The result is in the accumulator, store in the destination buffer. */
+    *pDst++ = sum0;
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* Processing is complete.         
+   ** Now copy the last numTaps - 1 samples to the start of the state buffer.       
+   ** This prepares the state buffer for the next function call. */
+
+  /* Points to the start of the state buffer */
+  pStateCurnt = S->pState;
+
+  /* Copy numTaps number of values */
+  i = (numTaps - 1u);
+
+  /* copy data */
+  while(i > 0u)
+  {
+    *pStateCurnt++ = *pState++;
+
+    /* Decrement the loop counter */
+    i--;
+  }
+
+#endif /*   #ifndef ARM_MATH_CM0        */
+
+}
+
+/**    
+ * @} end of FIR_decimate group    
+ */