arm_fir_f32.c

/* ----------------------------------------------------------------------  
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.  
*  
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*  
* Project: 	    CMSIS DSP Library  
* Title:	    arm_fir_f32.c  
*  
* Description:	Floating-point FIR filter processing function.  
*  
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* Redistribution and use in source and binary forms, with or without 
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the 
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* -------------------------------------------------------------------- */

#include "arm_math.h"

/**  
* @ingroup groupFilters  
*/

/**  
* @defgroup FIR Finite Impulse Response (FIR) Filters  
*  
* This set of functions implements Finite Impulse Response (FIR) filters  
* for Q7, Q15, Q31, and floating-point data types.  Fast versions of Q15 and Q31 are also provided.  
* The functions operate on blocks of input and output data and each call to the function processes  
* <code>blockSize</code> samples through the filter.  <code>pSrc</code> and  
* <code>pDst</code> points to input and output arrays containing <code>blockSize</code> values.  
*  
* \par Algorithm:  
* The FIR filter algorithm is based upon a sequence of multiply-accumulate (MAC) operations.  
* Each filter coefficient <code>b[n]</code> is multiplied by a state variable which equals a previous input sample <code>x[n]</code>.  
* <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>  
* \par  
* \image html FIR.gif "Finite Impulse Response filter"  
* \par  
* <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 following 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>  
* \par  
* Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code>.  
* The increased state buffer length allows circular addressing, which is traditionally used in the FIR filters,  
* to be avoided and yields a significant speed improvement.  
* 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 arrays cannot be shared.  
* There are separate instance structure declarations for each of the 4 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.  
* To do this manually without calling the init function, assign the follow subfields of the instance structure:
* numTaps, pCoeffs, pState. Also set all of the values in pState to zero. 
*  
* \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.  
* Set the values in the state buffer to zeros before static initialization.  
* The code below statically initializes each of the 4 different data type filter instance structures  
* <pre>  
*arm_fir_instance_f32 S = {numTaps, pState, pCoeffs};  
*arm_fir_instance_q31 S = {numTaps, pState, pCoeffs};  
*arm_fir_instance_q15 S = {numTaps, pState, pCoeffs};  
*arm_fir_instance_q7 S =  {numTaps, pState, pCoeffs};  
* </pre>  
*  
* where <code>numTaps</code> is the number of filter coefficients in the filter; <code>pState</code> is the address of the state buffer;  
* <code>pCoeffs</code> is the address of the coefficient buffer.  
*  
* \par Fixed-Point Behavior  
* Care must be taken when using the fixed-point versions of the FIR 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  
* @{  
*/

/**  
*  
* @param[in]  *S points to an instance of the floating-point FIR filter 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 samples to process per call.  
* @return     none.  
*  
*/

#if defined(ARM_MATH_CM7)

void arm_fir_f32(
const arm_fir_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 acc0, acc1, acc2, acc3, acc4, acc5, acc6, acc7;     /* Accumulators */
   float32_t x0, x1, x2, x3, x4, x5, x6, x7, 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;                    /* Loop counters */

   /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
   /* pStateCurnt points to the location where the new input data should be written */
   pStateCurnt = &(S->pState[(numTaps - 1u)]);

   /* Apply loop unrolling and compute 8 output values simultaneously.  
    * The variables acc0 ... acc7 hold output values that are being computed:  
    *  
    *    acc0 =  b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]  
    *    acc1 =  b[numTaps-1] * x[n-numTaps] +   b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]  
    *    acc2 =  b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] +   b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]  
    *    acc3 =  b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps]   +...+ b[0] * x[3]  
    */
   blkCnt = blockSize >> 3;

   /* First part of the processing with loop unrolling.  Compute 8 outputs at a time.  
   ** a second loop below computes the remaining 1 to 7 samples. */
   while(blkCnt > 0u)
   {
      /* Copy four new input samples into the state buffer */
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;

      /* Set all accumulators to zero */
      acc0 = 0.0f;
      acc1 = 0.0f;
      acc2 = 0.0f;
      acc3 = 0.0f;
      acc4 = 0.0f;
      acc5 = 0.0f;
      acc6 = 0.0f;
      acc7 = 0.0f;		

      /* Initialize state pointer */
      px = pState;

      /* Initialize coeff pointer */
      pb = (pCoeffs);		
   
      /* This is separated from the others to avoid 
       * a call to __aeabi_memmove which would be slower
       */
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;

      /* Read the first seven samples from the state buffer:  x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */
      x0 = *px++;
      x1 = *px++;
      x2 = *px++;
      x3 = *px++;
      x4 = *px++;
      x5 = *px++;
      x6 = *px++;

      /* Loop unrolling.  Process 8 taps at a time. */
      tapCnt = numTaps >> 3u;
      
      /* Loop over the number of taps.  Unroll by a factor of 8.  
       ** Repeat until we've computed numTaps-8 coefficients. */
      while(tapCnt > 0u)
      {
         /* Read the b[numTaps-1] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-3] sample */
         x7 = *(px++);

         /* acc0 +=  b[numTaps-1] * x[n-numTaps] */
         acc0 += x0 * c0;

         /* acc1 +=  b[numTaps-1] * x[n-numTaps-1] */
         acc1 += x1 * c0;

         /* acc2 +=  b[numTaps-1] * x[n-numTaps-2] */
         acc2 += x2 * c0;

         /* acc3 +=  b[numTaps-1] * x[n-numTaps-3] */
         acc3 += x3 * c0;

         /* acc4 +=  b[numTaps-1] * x[n-numTaps-4] */
         acc4 += x4 * c0;

         /* acc1 +=  b[numTaps-1] * x[n-numTaps-5] */
         acc5 += x5 * c0;

         /* acc2 +=  b[numTaps-1] * x[n-numTaps-6] */
         acc6 += x6 * c0;

         /* acc3 +=  b[numTaps-1] * x[n-numTaps-7] */
         acc7 += x7 * c0;
         
         /* Read the b[numTaps-2] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-4] sample */
         x0 = *(px++);

         /* Perform the multiply-accumulate */
         acc0 += x1 * c0;
         acc1 += x2 * c0;   
         acc2 += x3 * c0;   
         acc3 += x4 * c0;   
         acc4 += x5 * c0;   
         acc5 += x6 * c0;   
         acc6 += x7 * c0;   
         acc7 += x0 * c0;   
         
         /* Read the b[numTaps-3] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-5] sample */
         x1 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x2 * c0;
         acc1 += x3 * c0;   
         acc2 += x4 * c0;   
         acc3 += x5 * c0;   
         acc4 += x6 * c0;   
         acc5 += x7 * c0;   
         acc6 += x0 * c0;   
         acc7 += x1 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x2 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x3 * c0;
         acc1 += x4 * c0;   
         acc2 += x5 * c0;   
         acc3 += x6 * c0;   
         acc4 += x7 * c0;   
         acc5 += x0 * c0;   
         acc6 += x1 * c0;   
         acc7 += x2 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x3 = *(px++);
         /* Perform the multiply-accumulates */      
         acc0 += x4 * c0;
         acc1 += x5 * c0;   
         acc2 += x6 * c0;   
         acc3 += x7 * c0;   
         acc4 += x0 * c0;   
         acc5 += x1 * c0;   
         acc6 += x2 * c0;   
         acc7 += x3 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x4 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x5 * c0;
         acc1 += x6 * c0;   
         acc2 += x7 * c0;   
         acc3 += x0 * c0;   
         acc4 += x1 * c0;   
         acc5 += x2 * c0;   
         acc6 += x3 * c0;   
         acc7 += x4 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x5 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x6 * c0;
         acc1 += x7 * c0;   
         acc2 += x0 * c0;   
         acc3 += x1 * c0;   
         acc4 += x2 * c0;   
         acc5 += x3 * c0;   
         acc6 += x4 * c0;   
         acc7 += x5 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x6 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x7 * c0;
         acc1 += x0 * c0;   
         acc2 += x1 * c0;   
         acc3 += x2 * c0;   
         acc4 += x3 * c0;   
         acc5 += x4 * c0;   
         acc6 += x5 * c0;   
         acc7 += x6 * c0;   

         tapCnt--;
      }

      /* If the filter length is not a multiple of 8, compute the remaining filter taps */
      tapCnt = numTaps % 0x8u;

      while(tapCnt > 0u)
      {
         /* Read coefficients */
         c0 = *(pb++);

         /* Fetch 1 state variable */
         x7 = *(px++);

         /* Perform the multiply-accumulates */      
         acc0 += x0 * c0;
         acc1 += x1 * c0;   
         acc2 += x2 * c0;   
         acc3 += x3 * c0;   
         acc4 += x4 * c0;   
         acc5 += x5 * c0;   
         acc6 += x6 * c0;   
         acc7 += x7 * c0;   

         /* Reuse the present sample states for next sample */
         x0 = x1;
         x1 = x2;
         x2 = x3;
         x3 = x4;
         x4 = x5;
         x5 = x6;
         x6 = x7;

         /* Decrement the loop counter */
         tapCnt--;
      }

      /* Advance the state pointer by 8 to process the next group of 8 samples */
      pState = pState + 8;

      /* The results in the 8 accumulators, store in the destination buffer. */
      *pDst++ = acc0;
      *pDst++ = acc1;
      *pDst++ = acc2;
      *pDst++ = acc3;
      *pDst++ = acc4;
      *pDst++ = acc5;
      *pDst++ = acc6;
      *pDst++ = acc7;

      blkCnt--;
   }

   /* If the blockSize is not a multiple of 8, compute any remaining output samples here.  
   ** No loop unrolling is used. */
   blkCnt = blockSize % 0x8u;

   while(blkCnt > 0u)
   {
      /* Copy one sample at a time into state buffer */
      *pStateCurnt++ = *pSrc++;

      /* Set the accumulator to zero */
      acc0 = 0.0f;

      /* Initialize state pointer */
      px = pState;

      /* Initialize Coefficient pointer */
      pb = (pCoeffs);

      i = numTaps;

      /* Perform the multiply-accumulates */
      do
      {
         acc0 += *px++ * *pb++;
         i--;

      } while(i > 0u);

      /* The result is store in the destination buffer. */
      *pDst++ = acc0;

      /* Advance state pointer by 1 for the next sample */
      pState = pState + 1;

      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;

   tapCnt = (numTaps - 1u) >> 2u;

   /* copy data */
   while(tapCnt > 0u)
   {
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;

      /* Decrement the loop counter */
      tapCnt--;
   }

   /* Calculate remaining number of copies */
   tapCnt = (numTaps - 1u) % 0x4u;

   /* Copy the remaining q31_t data */
   while(tapCnt > 0u)
   {
      *pStateCurnt++ = *pState++;

      /* Decrement the loop counter */
      tapCnt--;
   }
}

#elif defined(ARM_MATH_CM0_FAMILY)

void arm_fir_f32(
const arm_fir_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 */
   uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */
   uint32_t i, tapCnt, blkCnt;                    /* Loop counters */

   /* Run the below code for Cortex-M0 */

   float32_t acc;

   /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
   /* pStateCurnt points to the location where the new input data should be written */
   pStateCurnt = &(S->pState[(numTaps - 1u)]);

   /* Initialize blkCnt with blockSize */
   blkCnt = blockSize;

   while(blkCnt > 0u)
   {
      /* Copy one sample at a time into state buffer */
      *pStateCurnt++ = *pSrc++;

      /* Set the accumulator to zero */
      acc = 0.0f;

      /* Initialize state pointer */
      px = pState;

      /* Initialize Coefficient pointer */
      pb = pCoeffs;

      i = numTaps;

      /* Perform the multiply-accumulates */
      do
      {
         /* acc =  b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */
         acc += *px++ * *pb++;
         i--;

      } while(i > 0u);

      /* The result is store in the destination buffer. */
      *pDst++ = acc;

      /* Advance state pointer by 1 for the next sample */
      pState = pState + 1;

      blkCnt--;
   }

   /* Processing is complete.         
   ** Now copy the last numTaps - 1 samples to the starting 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 */
   tapCnt = numTaps - 1u;

   /* Copy data */
   while(tapCnt > 0u)
   {
      *pStateCurnt++ = *pState++;

      /* Decrement the loop counter */
      tapCnt--;
   }

}

#else

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_f32(
const arm_fir_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 acc0, acc1, acc2, acc3, acc4, acc5, acc6, acc7;     /* Accumulators */
   float32_t x0, x1, x2, x3, x4, x5, x6, x7, 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;                    /* Loop counters */
   float32_t p0,p1,p2,p3,p4,p5,p6,p7;             /* Temporary product values */

   /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
   /* pStateCurnt points to the location where the new input data should be written */
   pStateCurnt = &(S->pState[(numTaps - 1u)]);

   /* Apply loop unrolling and compute 8 output values simultaneously.  
    * The variables acc0 ... acc7 hold output values that are being computed:  
    *  
    *    acc0 =  b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]  
    *    acc1 =  b[numTaps-1] * x[n-numTaps] +   b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]  
    *    acc2 =  b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] +   b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]  
    *    acc3 =  b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps]   +...+ b[0] * x[3]  
    */
   blkCnt = blockSize >> 3;

   /* First part of the processing with loop unrolling.  Compute 8 outputs at a time.  
   ** a second loop below computes the remaining 1 to 7 samples. */
   while(blkCnt > 0u)
   {
      /* Copy four new input samples into the state buffer */
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;

      /* Set all accumulators to zero */
      acc0 = 0.0f;
      acc1 = 0.0f;
      acc2 = 0.0f;
      acc3 = 0.0f;
      acc4 = 0.0f;
      acc5 = 0.0f;
      acc6 = 0.0f;
      acc7 = 0.0f;		

      /* Initialize state pointer */
      px = pState;

      /* Initialize coeff pointer */
      pb = (pCoeffs);		
   
      /* This is separated from the others to avoid 
       * a call to __aeabi_memmove which would be slower
       */
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;
      *pStateCurnt++ = *pSrc++;

      /* Read the first seven samples from the state buffer:  x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */
      x0 = *px++;
      x1 = *px++;
      x2 = *px++;
      x3 = *px++;
      x4 = *px++;
      x5 = *px++;
      x6 = *px++;

      /* Loop unrolling.  Process 8 taps at a time. */
      tapCnt = numTaps >> 3u;
      
      /* Loop over the number of taps.  Unroll by a factor of 8.  
       ** Repeat until we've computed numTaps-8 coefficients. */
      while(tapCnt > 0u)
      {
         /* Read the b[numTaps-1] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-3] sample */
         x7 = *(px++);

         /* acc0 +=  b[numTaps-1] * x[n-numTaps] */
         p0 = x0 * c0;

         /* acc1 +=  b[numTaps-1] * x[n-numTaps-1] */
         p1 = x1 * c0;

         /* acc2 +=  b[numTaps-1] * x[n-numTaps-2] */
         p2 = x2 * c0;

         /* acc3 +=  b[numTaps-1] * x[n-numTaps-3] */
         p3 = x3 * c0;

         /* acc4 +=  b[numTaps-1] * x[n-numTaps-4] */
         p4 = x4 * c0;

         /* acc1 +=  b[numTaps-1] * x[n-numTaps-5] */
         p5 = x5 * c0;

         /* acc2 +=  b[numTaps-1] * x[n-numTaps-6] */
         p6 = x6 * c0;

         /* acc3 +=  b[numTaps-1] * x[n-numTaps-7] */
         p7 = x7 * c0;
         
         /* Read the b[numTaps-2] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-4] sample */
         x0 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;


         /* Perform the multiply-accumulate */
         p0 = x1 * c0;
         p1 = x2 * c0;   
         p2 = x3 * c0;   
         p3 = x4 * c0;   
         p4 = x5 * c0;   
         p5 = x6 * c0;   
         p6 = x7 * c0;   
         p7 = x0 * c0;   
         
         /* Read the b[numTaps-3] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-5] sample */
         x1 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x2 * c0;
         p1 = x3 * c0;   
         p2 = x4 * c0;   
         p3 = x5 * c0;   
         p4 = x6 * c0;   
         p5 = x7 * c0;   
         p6 = x0 * c0;   
         p7 = x1 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x2 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x3 * c0;
         p1 = x4 * c0;   
         p2 = x5 * c0;   
         p3 = x6 * c0;   
         p4 = x7 * c0;   
         p5 = x0 * c0;   
         p6 = x1 * c0;   
         p7 = x2 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x3 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x4 * c0;
         p1 = x5 * c0;   
         p2 = x6 * c0;   
         p3 = x7 * c0;   
         p4 = x0 * c0;   
         p5 = x1 * c0;   
         p6 = x2 * c0;   
         p7 = x3 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x4 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x5 * c0;
         p1 = x6 * c0;   
         p2 = x7 * c0;   
         p3 = x0 * c0;   
         p4 = x1 * c0;   
         p5 = x2 * c0;   
         p6 = x3 * c0;   
         p7 = x4 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x5 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x6 * c0;
         p1 = x7 * c0;   
         p2 = x0 * c0;   
         p3 = x1 * c0;   
         p4 = x2 * c0;   
         p5 = x3 * c0;   
         p6 = x4 * c0;   
         p7 = x5 * c0;   

         /* Read the b[numTaps-4] coefficient */
         c0 = *(pb++);

         /* Read x[n-numTaps-6] sample */
         x6 = *(px++);
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Perform the multiply-accumulates */      
         p0 = x7 * c0;
         p1 = x0 * c0;   
         p2 = x1 * c0;   
         p3 = x2 * c0;   
         p4 = x3 * c0;   
         p5 = x4 * c0;   
         p6 = x5 * c0;   
         p7 = x6 * c0;   

         tapCnt--;
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;
      }

      /* If the filter length is not a multiple of 8, compute the remaining filter taps */
      tapCnt = numTaps % 0x8u;

      while(tapCnt > 0u)
      {
         /* Read coefficients */
         c0 = *(pb++);

         /* Fetch 1 state variable */
         x7 = *(px++);

         /* Perform the multiply-accumulates */      
         p0 = x0 * c0;
         p1 = x1 * c0;   
         p2 = x2 * c0;   
         p3 = x3 * c0;   
         p4 = x4 * c0;   
         p5 = x5 * c0;   
         p6 = x6 * c0;   
         p7 = x7 * c0;   

         /* Reuse the present sample states for next sample */
         x0 = x1;
         x1 = x2;
         x2 = x3;
         x3 = x4;
         x4 = x5;
         x5 = x6;
         x6 = x7;
         
         acc0 += p0;
         acc1 += p1;
         acc2 += p2;
         acc3 += p3;
         acc4 += p4;
         acc5 += p5;
         acc6 += p6;
         acc7 += p7;

         /* Decrement the loop counter */
         tapCnt--;
      }

      /* Advance the state pointer by 8 to process the next group of 8 samples */
      pState = pState + 8;

      /* The results in the 8 accumulators, store in the destination buffer. */
      *pDst++ = acc0;
      *pDst++ = acc1;
      *pDst++ = acc2;
      *pDst++ = acc3;
      *pDst++ = acc4;
      *pDst++ = acc5;
      *pDst++ = acc6;
      *pDst++ = acc7;

      blkCnt--;
   }

   /* If the blockSize is not a multiple of 8, compute any remaining output samples here.  
   ** No loop unrolling is used. */
   blkCnt = blockSize % 0x8u;

   while(blkCnt > 0u)
   {
      /* Copy one sample at a time into state buffer */
      *pStateCurnt++ = *pSrc++;

      /* Set the accumulator to zero */
      acc0 = 0.0f;

      /* Initialize state pointer */
      px = pState;

      /* Initialize Coefficient pointer */
      pb = (pCoeffs);

      i = numTaps;

      /* Perform the multiply-accumulates */
      do
      {
         acc0 += *px++ * *pb++;
         i--;

      } while(i > 0u);

      /* The result is store in the destination buffer. */
      *pDst++ = acc0;

      /* Advance state pointer by 1 for the next sample */
      pState = pState + 1;

      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;

   tapCnt = (numTaps - 1u) >> 2u;

   /* copy data */
   while(tapCnt > 0u)
   {
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;
      *pStateCurnt++ = *pState++;

      /* Decrement the loop counter */
      tapCnt--;
   }

   /* Calculate remaining number of copies */
   tapCnt = (numTaps - 1u) % 0x4u;

   /* Copy the remaining q31_t data */
   while(tapCnt > 0u)
   {
      *pStateCurnt++ = *pState++;

      /* Decrement the loop counter */
      tapCnt--;
   }
}

#endif 

/**  
* @} end of FIR group  
*/