File size: 4,395 Bytes
25ade36 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 | #include "edge-impulse-sdk/dsp/config.hpp"
#if EIDSP_LOAD_CMSIS_DSP_SOURCES
/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_linear_interp_f32.c
* Description: Floating-point linear interpolation
*
* $Date: 23 April 2021
* $Revision: V1.9.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2021 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 "edge-impulse-sdk/CMSIS/DSP/Include/dsp/interpolation_functions.h"
/**
@ingroup groupInterpolation
*/
/**
* @defgroup LinearInterpolate Linear Interpolation
*
* Linear interpolation is a method of curve fitting using linear polynomials.
* Linear interpolation works by effectively drawing a straight line between two neighboring samples and returning the appropriate point along that line
*
* \par
* \image html LinearInterp.gif "Linear interpolation"
*
* \par
* A Linear Interpolate function calculates an output value(y), for the input(x)
* using linear interpolation of the input values x0, x1( nearest input values) and the output values y0 and y1(nearest output values)
*
* \par Algorithm:
* <pre>
* y = y0 + (x - x0) * ((y1 - y0)/(x1-x0))
* where x0, x1 are nearest values of input x
* y0, y1 are nearest values to output y
* </pre>
*
* \par
* This set of functions implements Linear interpolation process
* for Q7, Q15, Q31, and floating-point data types. The functions operate on a single
* sample of data and each call to the function returns a single processed value.
* <code>S</code> points to an instance of the Linear Interpolate function data structure.
* <code>x</code> is the input sample value. The functions returns the output value.
*
* \par
* if x is outside of the table boundary, Linear interpolation returns first value of the table
* if x is below input range and returns last value of table if x is above range.
*/
/**
* @addtogroup LinearInterpolate
* @{
*/
/**
* @brief Process function for the floating-point Linear Interpolation Function.
* @param[in,out] S is an instance of the floating-point Linear Interpolation structure
* @param[in] x input sample to process
* @return y processed output sample.
*
*/
float32_t arm_linear_interp_f32(
arm_linear_interp_instance_f32 * S,
float32_t x)
{
float32_t y;
float32_t x0, x1; /* Nearest input values */
float32_t y0, y1; /* Nearest output values */
float32_t xSpacing = S->xSpacing; /* spacing between input values */
int32_t i; /* Index variable */
float32_t *pYData = S->pYData; /* pointer to output table */
/* Calculation of index */
i = (int32_t) ((x - S->x1) / xSpacing);
if (i < 0)
{
/* Iniatilize output for below specified range as least output value of table */
y = pYData[0];
}
else if ((uint32_t)i >= (S->nValues - 1))
{
/* Iniatilize output for above specified range as last output value of table */
y = pYData[S->nValues - 1];
}
else
{
/* Calculation of nearest input values */
x0 = S->x1 + i * xSpacing;
x1 = S->x1 + (i + 1) * xSpacing;
/* Read of nearest output values */
y0 = pYData[i];
y1 = pYData[i + 1];
/* Calculation of output */
y = y0 + (x - x0) * ((y1 - y0) / (x1 - x0));
}
/* returns output value */
return (y);
}
/**
* @} end of LinearInterpolate group
*/
#endif // EIDSP_LOAD_CMSIS_DSP_SOURCES
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