pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / FilteringFunctions / arm_fir_lattice_q31.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_lattice_q31.c | |

* | |

* Description: Q31 FIR lattice 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; | |

* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | |

* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |

* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN | |

* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |

* POSSIBILITY OF SUCH DAMAGE. | |

* -------------------------------------------------------------------- */ | |

#include "arm_math.h" | |

/** | |

* @ingroup groupFilters | |

*/ | |

/** | |

* @addtogroup FIR_Lattice | |

* @{ | |

*/ | |

/** | |

* @brief Processing function for the Q31 FIR lattice filter. | |

* @param[in] *S points to an instance of the Q31 FIR lattice 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. | |

* @return none. | |

* | |

* @details | |

* <b>Scaling and Overflow Behavior:</b> | |

* In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits. | |

*/ | |

#ifndef ARM_MATH_CM0_FAMILY | |

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

void arm_fir_lattice_q31( | |

const arm_fir_lattice_instance_q31 * S, | |

q31_t * pSrc, | |

q31_t * pDst, | |

uint32_t blockSize) | |

{ | |

q31_t *pState; /* State pointer */ | |

q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ | |

q31_t *px; /* temporary state pointer */ | |

q31_t *pk; /* temporary coefficient pointer */ | |

q31_t fcurr1, fnext1, gcurr1 = 0, gnext1; /* temporary variables for first sample in loop unrolling */ | |

q31_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */ | |

uint32_t numStages = S->numStages; /* Length of the filter */ | |

uint32_t blkCnt, stageCnt; /* temporary variables for counts */ | |

q31_t k; | |

pState = &S->pState[0]; | |

blkCnt = blockSize >> 1u; | |

/* First part of the processing with loop unrolling. Compute 2 outputs at a time. | |

a second loop below computes the remaining 1 sample. */ | |

while(blkCnt > 0u) | |

{ | |

/* f0(n) = x(n) */ | |

fcurr1 = *pSrc++; | |

/* f0(n) = x(n) */ | |

fcurr2 = *pSrc++; | |

/* Initialize coeff pointer */ | |

pk = (pCoeffs); | |

/* Initialize state pointer */ | |

px = pState; | |

/* read g0(n - 1) from state buffer */ | |

gcurr1 = *px; | |

/* Read the reflection coefficient */ | |

k = *pk++; | |

/* for sample 1 processing */ | |

/* f1(n) = f0(n) + K1 * g0(n-1) */ | |

fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32); | |

/* g1(n) = f0(n) * K1 + g0(n-1) */ | |

gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32); | |

fnext1 = fcurr1 + (fnext1 << 1u); | |

gnext1 = gcurr1 + (gnext1 << 1u); | |

/* for sample 1 processing */ | |

/* f1(n) = f0(n) + K1 * g0(n-1) */ | |

fnext2 = (q31_t) (((q63_t) fcurr1 * k) >> 32); | |

/* g1(n) = f0(n) * K1 + g0(n-1) */ | |

gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32); | |

fnext2 = fcurr2 + (fnext2 << 1u); | |

gnext2 = fcurr1 + (gnext2 << 1u); | |

/* save g1(n) in state buffer */ | |

*px++ = fcurr2; | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr1 = fnext1; | |

fcurr2 = fnext2; | |

stageCnt = (numStages - 1u); | |

/* stage loop */ | |

while(stageCnt > 0u) | |

{ | |

/* Read the reflection coefficient */ | |

k = *pk++; | |

/* read g2(n) from state buffer */ | |

gcurr1 = *px; | |

/* save g1(n) in state buffer */ | |

*px++ = gnext2; | |

/* Sample processing for K2, K3.... */ | |

/* f2(n) = f1(n) + K2 * g1(n-1) */ | |

fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32); | |

fnext2 = (q31_t) (((q63_t) gnext1 * k) >> 32); | |

fnext1 = fcurr1 + (fnext1 << 1u); | |

fnext2 = fcurr2 + (fnext2 << 1u); | |

/* g2(n) = f1(n) * K2 + g1(n-1) */ | |

gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32); | |

gnext2 = gnext1 + (gnext2 << 1u); | |

/* g2(n) = f1(n) * K2 + g1(n-1) */ | |

gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32); | |

gnext1 = gcurr1 + (gnext1 << 1u); | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr1 = fnext1; | |

fcurr2 = fnext2; | |

stageCnt--; | |

} | |

/* y(n) = fN(n) */ | |

*pDst++ = fcurr1; | |

*pDst++ = fcurr2; | |

blkCnt--; | |

} | |

/* If the blockSize is not a multiple of 4, compute any remaining output samples here. | |

** No loop unrolling is used. */ | |

blkCnt = blockSize % 0x2u; | |

while(blkCnt > 0u) | |

{ | |

/* f0(n) = x(n) */ | |

fcurr1 = *pSrc++; | |

/* Initialize coeff pointer */ | |

pk = (pCoeffs); | |

/* Initialize state pointer */ | |

px = pState; | |

/* read g0(n - 1) from state buffer */ | |

gcurr1 = *px; | |

/* Read the reflection coefficient */ | |

k = *pk++; | |

/* for sample 1 processing */ | |

/* f1(n) = f0(n) + K1 * g0(n-1) */ | |

fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32); | |

fnext1 = fcurr1 + (fnext1 << 1u); | |

/* g1(n) = f0(n) * K1 + g0(n-1) */ | |

gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32); | |

gnext1 = gcurr1 + (gnext1 << 1u); | |

/* save g1(n) in state buffer */ | |

*px++ = fcurr1; | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr1 = fnext1; | |

stageCnt = (numStages - 1u); | |

/* stage loop */ | |

while(stageCnt > 0u) | |

{ | |

/* Read the reflection coefficient */ | |

k = *pk++; | |

/* read g2(n) from state buffer */ | |

gcurr1 = *px; | |

/* save g1(n) in state buffer */ | |

*px++ = gnext1; | |

/* Sample processing for K2, K3.... */ | |

/* f2(n) = f1(n) + K2 * g1(n-1) */ | |

fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32); | |

fnext1 = fcurr1 + (fnext1 << 1u); | |

/* g2(n) = f1(n) * K2 + g1(n-1) */ | |

gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32); | |

gnext1 = gcurr1 + (gnext1 << 1u); | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr1 = fnext1; | |

stageCnt--; | |

} | |

/* y(n) = fN(n) */ | |

*pDst++ = fcurr1; | |

blkCnt--; | |

} | |

} | |

#else | |

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

void arm_fir_lattice_q31( | |

const arm_fir_lattice_instance_q31 * S, | |

q31_t * pSrc, | |

q31_t * pDst, | |

uint32_t blockSize) | |

{ | |

q31_t *pState; /* State pointer */ | |

q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ | |

q31_t *px; /* temporary state pointer */ | |

q31_t *pk; /* temporary coefficient pointer */ | |

q31_t fcurr, fnext, gcurr, gnext; /* temporary variables */ | |

uint32_t numStages = S->numStages; /* Length of the filter */ | |

uint32_t blkCnt, stageCnt; /* temporary variables for counts */ | |

pState = &S->pState[0]; | |

blkCnt = blockSize; | |

while(blkCnt > 0u) | |

{ | |

/* f0(n) = x(n) */ | |

fcurr = *pSrc++; | |

/* Initialize coeff pointer */ | |

pk = (pCoeffs); | |

/* Initialize state pointer */ | |

px = pState; | |

/* read g0(n-1) from state buffer */ | |

gcurr = *px; | |

/* for sample 1 processing */ | |

/* f1(n) = f0(n) + K1 * g0(n-1) */ | |

fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr; | |

/* g1(n) = f0(n) * K1 + g0(n-1) */ | |

gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr; | |

/* save g1(n) in state buffer */ | |

*px++ = fcurr; | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr = fnext; | |

stageCnt = (numStages - 1u); | |

/* stage loop */ | |

while(stageCnt > 0u) | |

{ | |

/* read g2(n) from state buffer */ | |

gcurr = *px; | |

/* save g1(n) in state buffer */ | |

*px++ = gnext; | |

/* Sample processing for K2, K3.... */ | |

/* f2(n) = f1(n) + K2 * g1(n-1) */ | |

fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr; | |

/* g2(n) = f1(n) * K2 + g1(n-1) */ | |

gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr; | |

/* f1(n) is saved in fcurr1 | |

for next stage processing */ | |

fcurr = fnext; | |

stageCnt--; | |

} | |

/* y(n) = fN(n) */ | |

*pDst++ = fcurr; | |

blkCnt--; | |

} | |

} | |

#endif /* #ifndef ARM_MATH_CM0_FAMILY */ | |

/** | |

* @} end of FIR_Lattice group | |

*/ |