hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_lms_q15.c

/* ----------------------------------------------------------------------   
* Copyright (C) 2010 ARM Limited. All rights reserved.   
*   
* $Date:        15. July 2011  
* $Revision: 	V1.0.10  
*   
* Project: 	    CMSIS DSP Library   
* Title:	    arm_lms_q15.c   
*   
* Description:	Processing function for the Q15 LMS filter.   
*   
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* 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   
 */

/**   
 * @addtogroup LMS   
 * @{   
 */

 /**   
 * @brief Processing function for Q15 LMS filter.   
 * @param[in] *S points to an instance of the Q15 LMS filter structure.   
 * @param[in] *pSrc points to the block of input data.   
 * @param[in] *pRef points to the block of reference data.   
 * @param[out] *pOut points to the block of output data.   
 * @param[out] *pErr points to the block of error data.   
 * @param[in] blockSize number of samples to process.   
 * @return none.   
 *   
 * \par Scaling and Overflow Behavior:   
 * The function is implemented using a 64-bit internal accumulator.   
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.   
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.   
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.   
 * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.   
 * Lastly, the accumulator is saturated to yield a result in 1.15 format.   
 *  
 * \par  
 * 	In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted.  
 *   
 */

void arm_lms_q15(
  const arm_lms_instance_q15 * S,
  q15_t * pSrc,
  q15_t * pRef,
  q15_t * pOut,
  q15_t * pErr,
  uint32_t blockSize)
{
  q15_t *pState = S->pState;                     /* State pointer */
  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */
  q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
  q15_t *pStateCurnt;                            /* Points to the current sample of the state */
  q15_t mu = S->mu;                              /* Adaptive factor */
  q15_t *px;                                     /* Temporary pointer for state */
  q15_t *pb;                                     /* Temporary pointer for coefficient buffer */
  uint32_t tapCnt, blkCnt;                       /* Loop counters */
  q63_t acc;                                     /* Accumulator */
  q15_t e = 0;                                   /* error of data sample */
  q15_t alpha;                                   /* Intermediate constant for taps update */
  uint32_t shift = S->postShift + 1u;            /* Shift to be applied to the output */


#ifndef ARM_MATH_CM0

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

  q31_t coef;                                    /* Teporary variable for coefficient */

  /* S->pState points to buffer 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)]);

  /* Initializing blkCnt with blockSize */
  blkCnt = blockSize;

  while(blkCnt > 0u)
  {
    /* Copy the new input sample into the state buffer */
    *pStateCurnt++ = *pSrc++;

    /* Initialize state pointer */
    px = pState;

    /* Initialize coefficient pointer */
    pb = pCoeffs;

    /* Set the accumulator to zero */
    acc = 0;

    /* Loop unrolling.  Process 4 taps at a time. */
    tapCnt = numTaps >> 2u;

    while(tapCnt > 0u)
    {
      /* acc +=  b[N] * x[n-N] + b[N-1] * x[n-N-1] */
      /* Perform the multiply-accumulate */
      acc = __SMLALD(*__SIMD32(px)++, (*__SIMD32(pb)++), acc);
      acc = __SMLALD(*__SIMD32(px)++, (*__SIMD32(pb)++), acc);

      /* 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)
    {
      /* Perform the multiply-accumulate */
      acc += (q63_t) (((q31_t) (*px++) * (*pb++)));

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

    /* Converting the result to 1.15 format and saturate the output */
    acc = __SSAT((acc >> (16 - shift)), 16);

    /* Store the result from accumulator into the destination buffer. */
    *pOut++ = (q15_t) acc;

    /* Compute and store error */
    e = *pRef++ - (q15_t) acc;

    *pErr++ = (q15_t) e;

    /* Compute alpha i.e. intermediate constant for taps update */
    alpha = (q15_t) (((q31_t) e * (mu)) >> 15);

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

    /* Initialize coefficient pointer */
    pb = pCoeffs;

    /* Loop unrolling.  Process 4 taps at a time. */
    tapCnt = numTaps >> 2u;

    /* Update filter coefficients */
    while(tapCnt > 0u)
    {
      coef = (q31_t) * pb + (((q31_t) alpha * (*px++)) >> 15);
      *pb++ = (q15_t) __SSAT((coef), 16);
      coef = (q31_t) * pb + (((q31_t) alpha * (*px++)) >> 15);
      *pb++ = (q15_t) __SSAT((coef), 16);
      coef = (q31_t) * pb + (((q31_t) alpha * (*px++)) >> 15);
      *pb++ = (q15_t) __SSAT((coef), 16);
      coef = (q31_t) * pb + (((q31_t) alpha * (*px++)) >> 15);
      *pb++ = (q15_t) __SSAT((coef), 16);

      /* 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)
    {
      /* Perform the multiply-accumulate */
      coef = (q31_t) * pb + (((q31_t) alpha * (*px++)) >> 15);
      *pb++ = (q15_t) __SSAT((coef), 16);

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

    /* Decrement the loop counter */
    blkCnt--;

  }

  /* 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 pState buffer */
  pStateCurnt = S->pState;

  /* Calculation of count for copying integer writes */
  tapCnt = (numTaps - 1u) >> 2;

  while(tapCnt > 0u)
  {

    *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
    *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;

    tapCnt--;

  }

  /* Calculation of count for remaining q15_t data */
  tapCnt = (numTaps - 1u) % 0x4u;

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

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

#else

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

  /* S->pState points to buffer 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)]);

  /* Loop over blockSize number of values */
  blkCnt = blockSize;

  while(blkCnt > 0u)
  {
    /* Copy the new input sample into the state buffer */
    *pStateCurnt++ = *pSrc++;

    /* Initialize pState pointer */
    px = pState;

    /* Initialize pCoeffs pointer */
    pb = pCoeffs;

    /* Set the accumulator to zero */
    acc = 0;

    /* Loop over numTaps number of values */
    tapCnt = numTaps;

    while(tapCnt > 0u)
    {
      /* Perform the multiply-accumulate */
      acc += (q63_t) ((q31_t) (*px++) * (*pb++));

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

    /* Converting the result to 1.15 format and saturate the output */
    acc = __SSAT((acc >> (16 - shift)), 16);

    /* Store the result from accumulator into the destination buffer. */
    *pOut++ = (q15_t) acc;

    /* Compute and store error */
    e = *pRef++ - (q15_t) acc;

    *pErr++ = (q15_t) e;

    /* Compute alpha i.e. intermediate constant for taps update */
    alpha = (q15_t) (((q31_t) e * (mu)) >> 15);

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

    /* Initialize pCoeffs pointer */
    pb = pCoeffs;

    /* Loop over numTaps number of values */
    tapCnt = numTaps;

    while(tapCnt > 0u)
    {
      /* Perform the multiply-accumulate */
      *pb++ += (q15_t) (((q31_t) alpha * (*px++)) >> 15);

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

    /* 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 pState buffer */
  pStateCurnt = S->pState;

  /*  Copy (numTaps - 1u) samples  */
  tapCnt = (numTaps - 1u);

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

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

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**   
   * @} end of LMS group   
   */