| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_init_q15.c |
| * Description: Q15 FIR filter initialization function |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 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 FIR |
| @{ |
| */ |
| |
| /** |
| @brief Initialization function for the Q15 FIR filter. |
| @param[in,out] S points to an instance of the Q15 FIR filter structure. |
| @param[in] numTaps number of filter coefficients in the filter. Must be even and greater than or equal to 4. |
| @param[in] pCoeffs points to the filter coefficients buffer. |
| @param[in] pState points to the state buffer. |
| @param[in] blockSize number of samples processed per call. |
| @return execution status |
| - \ref ARM_MATH_SUCCESS : Operation successful |
| - \ref ARM_MATH_ARGUMENT_ERROR : <code>numTaps</code> is not greater than or equal to 4 and even |
| |
| @par Details |
| <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order: |
| <pre> |
| {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]} |
| </pre> |
| Note that <code>numTaps</code> must be even and greater than or equal to 4. |
| To implement an odd length filter simply increase <code>numTaps</code> by 1 and set the last coefficient to zero. |
| For example, to implement a filter with <code>numTaps=3</code> and coefficients |
| <pre> |
| {0.3, -0.8, 0.3} |
| </pre> |
| set <code>numTaps=4</code> and use the coefficients: |
| <pre> |
| {0.3, -0.8, 0.3, 0}. |
| </pre> |
| Similarly, to implement a two point filter |
| <pre> |
| {0.3, -0.3} |
| </pre> |
| set <code>numTaps=4</code> and use the coefficients: |
| <pre> |
| {0.3, -0.3, 0, 0}. |
| </pre> |
| <code>pState</code> points to the array of state variables. |
| <code>pState</code> is of length <code>numTaps+blockSize</code>, when running on Cortex-M4 and Cortex-M3 and is of length <code>numTaps+blockSize-1</code>, when running on Cortex-M0 where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_q15()</code>. |
| */ |
| |
| arm_status arm_fir_init_q15( |
| arm_fir_instance_q15 * S, |
| uint16_t numTaps, |
| const q15_t * pCoeffs, |
| q15_t * pState, |
| uint32_t blockSize) |
| { |
| arm_status status; |
| |
| #if defined (ARM_MATH_DSP) |
| |
| /* The Number of filter coefficients in the filter must be even and at least 4 */ |
| if (numTaps & 0x1U) |
| { |
| status = ARM_MATH_ARGUMENT_ERROR; |
| } |
| else |
| { |
| /* Assign filter taps */ |
| S->numTaps = numTaps; |
| |
| /* Assign coefficient pointer */ |
| S->pCoeffs = pCoeffs; |
| |
| /* Clear the state buffer. The size is always (blockSize + numTaps ) */ |
| memset(pState, 0, (numTaps + (blockSize)) * sizeof(q15_t)); |
| |
| /* Assign state pointer */ |
| S->pState = pState; |
| |
| status = ARM_MATH_SUCCESS; |
| } |
| |
| return (status); |
| |
| #else |
| |
| /* Assign filter taps */ |
| S->numTaps = numTaps; |
| |
| /* Assign coefficient pointer */ |
| S->pCoeffs = pCoeffs; |
| |
| /* Clear state buffer. The size is always (blockSize + numTaps - 1) */ |
| memset(pState, 0, (numTaps + (blockSize - 1U)) * sizeof(q15_t)); |
| |
| /* Assign state pointer */ |
| S->pState = pState; |
| |
| status = ARM_MATH_SUCCESS; |
| |
| return (status); |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| } |
| |
| /** |
| @} end of FIR group |
| */ |