95 lines
2.8 KiB
C
95 lines
2.8 KiB
C
/****************************************************************************
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* libs/libdsp/lib_avg.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <assert.h>
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#include <dsp.h>
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#include <string.h>
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/* Based on video explanation of Dr. Shane Ross:
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* https://www.youtube.com/watch?v=HCd-leV8OkU
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*/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: avg_filter_data_init
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*
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* Description:
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* Initialize the data struct used to store prev_avg and k parameter.
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*
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* Input Parameters:
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* data - pointer to avg_filter_data_s
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* prev_avg - initial value of prev_avg
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* k - initial value of k counter
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void avg_filter_data_init(FAR struct avg_filter_data_s *data,
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float prev_avg, float k)
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{
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LIBDSP_DEBUGASSERT(k > 0.0f)
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data->prev_avg = prev_avg;
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data->k = k;
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}
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/****************************************************************************
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* Name: avg_filter
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*
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* Description:
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* Calculate the recurring average of a signal in the time
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*
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* Input Parameters:
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* prev_avg - pointer to previous average variable
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* k - pointer to k counter variable
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* x - current signal value
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*
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* Returned Value:
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* Average value
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*
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****************************************************************************/
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float avg_filter(FAR struct avg_filter_data_s *data, float x)
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{
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float alpha;
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float avg;
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LIBDSP_DEBUGASSERT(data != NULL);
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alpha = (data->k - 1.0f) / data->k;
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avg = (alpha * data->prev_avg) + ((1.0f - alpha) * x);
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data->k += 1.0f;
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data->prev_avg = avg;
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return avg;
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}
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