The CMSIS DSP 5 library
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functions/FilteringFunctions/arm_biquad_cascade_df1_init_q31.c
- Committer:
- xorjoep
- Date:
- 2018-06-21
- Revision:
- 3:4098b9d3d571
- Parent:
- 1:24714b45cd1b
File content as of revision 3:4098b9d3d571:
/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_biquad_cascade_df1_init_q31.c * Description: Q31 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 * * @param[in,out] *S points to an instance of the Q31 Biquad cascade structure. * @param[in] numStages number of 2nd order stages in the filter. * @param[in] *pCoeffs points to the filter coefficients buffer. * @param[in] *pState points to the state buffer. * @param[in] postShift Shift to be applied after the accumulator. Varies according to the coefficients format * @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> * 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> points to state variables 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_q31( arm_biquad_casd_df1_inst_q31 * S, uint8_t numStages, q31_t * pCoeffs, q31_t * pState, int8_t postShift) { /* Assign filter stages */ S->numStages = numStages; /* Assign postShift to be applied to the output */ S->postShift = postShift; /* Assign coefficient pointer */ S->pCoeffs = pCoeffs; /* Clear state buffer and size is always 4 * numStages */ memset(pState, 0, (4U * (uint32_t) numStages) * sizeof(q31_t)); /* Assign state pointer */ S->pState = pState; } /** * @} end of BiquadCascadeDF1 group */