pigweed / third_party / github / STMicroelectronics / cmsis_core / cb6d9400754e6c9050487dfa573949b61152ac99 / . / DSP / Source / FilteringFunctions / arm_biquad_cascade_df1_init_f32.c

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

* Project: CMSIS DSP Library | |

* Title: arm_biquad_cascade_df1_init_f32.c | |

* Description: Floating-point Biquad cascade DirectFormI(DF1) filter initialization function | |

* | |

* $Date: 27. January 2017 | |

* $Revision: V.1.5.1 | |

* | |

* Target Processor: Cortex-M cores | |

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

/* | |

* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. | |

* | |

* SPDX-License-Identifier: Apache-2.0 | |

* | |

* Licensed under the Apache License, Version 2.0 (the License); you may | |

* not use this file except in compliance with the License. | |

* You may obtain a copy of the License at | |

* | |

* www.apache.org/licenses/LICENSE-2.0 | |

* | |

* Unless required by applicable law or agreed to in writing, software | |

* distributed under the License is distributed on an AS IS BASIS, WITHOUT | |

* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |

* See the License for the specific language governing permissions and | |

* limitations under the License. | |

*/ | |

#include "arm_math.h" | |

/** | |

* @ingroup groupFilters | |

*/ | |

/** | |

* @addtogroup BiquadCascadeDF1 | |

* @{ | |

*/ | |

/** | |

* @details | |

* @brief Initialization function for the floating-point Biquad cascade filter. | |

* @param[in,out] *S points to an instance of the floating-point Biquad cascade structure. | |

* @param[in] numStages number of 2nd order stages in the filter. | |

* @param[in] *pCoeffs points to the filter coefficients array. | |

* @param[in] *pState points to the state array. | |

* @return none | |

* | |

* | |

* <b>Coefficient and State Ordering:</b> | |

* | |

* \par | |

* The coefficients are stored in the array <code>pCoeffs</code> in the following order: | |

* <pre> | |

* {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...} | |

* </pre> | |

* | |

* \par | |

* where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage, | |

* <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage, | |

* and so on. The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values. | |

* | |

* \par | |

* The <code>pState</code> is a pointer to state array. | |

* Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>. | |

* The state variables are arranged in the <code>pState</code> array as: | |

* <pre> | |

* {x[n-1], x[n-2], y[n-1], y[n-2]} | |

* </pre> | |

* The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on. | |

* The state array has a total length of <code>4*numStages</code> values. | |

* The state variables are updated after each block of data is processed; the coefficients are untouched. | |

* | |

*/ | |

void arm_biquad_cascade_df1_init_f32( | |

arm_biquad_casd_df1_inst_f32 * S, | |

uint8_t numStages, | |

float32_t * pCoeffs, | |

float32_t * pState) | |

{ | |

/* Assign filter stages */ | |

S->numStages = numStages; | |

/* Assign coefficient pointer */ | |

S->pCoeffs = pCoeffs; | |

/* Clear state buffer and size is always 4 * numStages */ | |

memset(pState, 0, (4U * (uint32_t) numStages) * sizeof(float32_t)); | |

/* Assign state pointer */ | |

S->pState = pState; | |

} | |

/** | |

* @} end of BiquadCascadeDF1 group | |

*/ |