192 lines
8.4 KiB
C
192 lines
8.4 KiB
C
/*
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* $NetBSD: sensirion_voc_algorithm.h,v 1.2 2022/09/25 12:41:46 andvar Exp $
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*/
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/*
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* Copyright (c) 2021, Sensirion AG
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* * Neither the name of Sensirion AG nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef VOCALGORITHM_H_
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#define VOCALGORITHM_H_
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#include "sensirion_arch_config.h"
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/* The fixed point arithmetic parts of this code were originally created by
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* https://github.com/PetteriAimonen/libfixmath
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*/
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typedef int32_t fix16_t;
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#define F16(x) \
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((fix16_t)(((x) >= 0) ? ((x)*65536.0 + 0.5) : ((x)*65536.0 - 0.5)))
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// Should be set by the building toolchain
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#ifndef LIBRARY_VERSION_NAME
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#define LIBRARY_VERSION_NAME "custom build"
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#endif
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#define VocAlgorithm_SAMPLING_INTERVAL (1.)
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#define VocAlgorithm_INITIAL_BLACKOUT (45.)
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#define VocAlgorithm_VOC_INDEX_GAIN (230.)
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#define VocAlgorithm_SRAW_STD_INITIAL (50.)
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#define VocAlgorithm_SRAW_STD_BONUS (220.)
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#define VocAlgorithm_TAU_MEAN_VARIANCE_HOURS (12.)
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#define VocAlgorithm_TAU_INITIAL_MEAN (20.)
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#define VocAlgorithm_INIT_DURATION_MEAN ((3600. * 0.75))
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#define VocAlgorithm_INIT_TRANSITION_MEAN (0.01)
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#define VocAlgorithm_TAU_INITIAL_VARIANCE (2500.)
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#define VocAlgorithm_INIT_DURATION_VARIANCE ((3600. * 1.45))
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#define VocAlgorithm_INIT_TRANSITION_VARIANCE (0.01)
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#define VocAlgorithm_GATING_THRESHOLD (340.)
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#define VocAlgorithm_GATING_THRESHOLD_INITIAL (510.)
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#define VocAlgorithm_GATING_THRESHOLD_TRANSITION (0.09)
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#define VocAlgorithm_GATING_MAX_DURATION_MINUTES ((60. * 3.))
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#define VocAlgorithm_GATING_MAX_RATIO (0.3)
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#define VocAlgorithm_SIGMOID_L (500.)
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#define VocAlgorithm_SIGMOID_K (-0.0065)
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#define VocAlgorithm_SIGMOID_X0 (213.)
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#define VocAlgorithm_VOC_INDEX_OFFSET_DEFAULT (100.)
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#define VocAlgorithm_LP_TAU_FAST (20.0)
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#define VocAlgorithm_LP_TAU_SLOW (500.0)
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#define VocAlgorithm_LP_ALPHA (-0.2)
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#define VocAlgorithm_PERSISTENCE_UPTIME_GAMMA ((3. * 3600.))
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#define VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING (64.)
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#define VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__FIX16_MAX (32767.)
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/**
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* Struct to hold all the states of the VOC algorithm.
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*/
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typedef struct {
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fix16_t mVoc_Index_Offset;
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fix16_t mTau_Mean_Variance_Hours;
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fix16_t mGating_Max_Duration_Minutes;
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fix16_t mSraw_Std_Initial;
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fix16_t mUptime;
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fix16_t mSraw;
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fix16_t mVoc_Index;
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fix16_t m_Mean_Variance_Estimator__Gating_Max_Duration_Minutes;
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bool m_Mean_Variance_Estimator___Initialized;
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fix16_t m_Mean_Variance_Estimator___Mean;
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fix16_t m_Mean_Variance_Estimator___Sraw_Offset;
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fix16_t m_Mean_Variance_Estimator___Std;
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fix16_t m_Mean_Variance_Estimator___Gamma;
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fix16_t m_Mean_Variance_Estimator___Gamma_Initial_Mean;
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fix16_t m_Mean_Variance_Estimator___Gamma_Initial_Variance;
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fix16_t m_Mean_Variance_Estimator__Gamma_Mean;
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fix16_t m_Mean_Variance_Estimator__Gamma_Variance;
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fix16_t m_Mean_Variance_Estimator___Uptime_Gamma;
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fix16_t m_Mean_Variance_Estimator___Uptime_Gating;
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fix16_t m_Mean_Variance_Estimator___Gating_Duration_Minutes;
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fix16_t m_Mean_Variance_Estimator___Sigmoid__L;
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fix16_t m_Mean_Variance_Estimator___Sigmoid__K;
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fix16_t m_Mean_Variance_Estimator___Sigmoid__X0;
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fix16_t m_Mox_Model__Sraw_Std;
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fix16_t m_Mox_Model__Sraw_Mean;
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fix16_t m_Sigmoid_Scaled__Offset;
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fix16_t m_Adaptive_Lowpass__A1;
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fix16_t m_Adaptive_Lowpass__A2;
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bool m_Adaptive_Lowpass___Initialized;
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fix16_t m_Adaptive_Lowpass___X1;
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fix16_t m_Adaptive_Lowpass___X2;
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fix16_t m_Adaptive_Lowpass___X3;
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} VocAlgorithmParams;
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/**
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* Initialize the VOC algorithm parameters. Call this once at the beginning or
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* whenever the sensor stopped measurements.
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* @param params Pointer to the VocAlgorithmParams struct
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*/
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void VocAlgorithm_init(VocAlgorithmParams* params);
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/**
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* Get current algorithm states. Retrieved values can be used in
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* VocAlgorithm_set_states() to resume operation after a short interruption,
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* skipping initial learning phase. This feature can only be used after at least
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* 3 hours of continuous operation.
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* @param params Pointer to the VocAlgorithmParams struct
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* @param state0 State0 to be stored
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* @param state1 State1 to be stored
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*/
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void VocAlgorithm_get_states(VocAlgorithmParams* params, int32_t* state0,
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int32_t* state1);
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/**
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* Set previously retrieved algorithm states to resume operation after a short
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* interruption, skipping initial learning phase. This feature should not be
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* used after interruptions of more than 10 minutes. Call this once after
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* VocAlgorithm_init() and the optional VocAlgorithm_set_tuning_parameters(), if
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* desired. Otherwise, the algorithm will start with initial learning phase.
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* @param params Pointer to the VocAlgorithmParams struct
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* @param state0 State0 to be restored
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* @param state1 State1 to be restored
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*/
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void VocAlgorithm_set_states(VocAlgorithmParams* params, int32_t state0,
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int32_t state1);
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/**
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* Set parameters to customize the VOC algorithm. Call this once after
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* VocAlgorithm_init(), if desired. Otherwise, the default values will be used.
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*
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* @param params Pointer to the VocAlgorithmParams struct
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* @param voc_index_offset VOC index representing typical (average)
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* conditions. Range 1..250, default 100
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* @param learning_time_hours Time constant of long-term estimator.
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* Past events will be forgotten after about
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* twice the learning time.
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* Range 1..72 [hours], default 12 [hours]
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* @param gating_max_duration_minutes Maximum duration of gating (freeze of
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* estimator during high VOC index signal).
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* 0 (no gating) or range 1..720 [minutes],
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* default 180 [minutes]
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* @param std_initial Initial estimate for standard deviation.
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* Lower value boosts events during initial
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* learning period, but may result in larger
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* device-to-device variations.
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* Range 10..500, default 50
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*/
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void VocAlgorithm_set_tuning_parameters(VocAlgorithmParams* params,
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int32_t voc_index_offset,
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int32_t learning_time_hours,
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int32_t gating_max_duration_minutes,
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int32_t std_initial);
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/**
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* Calculate the VOC index value from the raw sensor value.
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*
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* @param params Pointer to the VocAlgorithmParams struct
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* @param sraw Raw value from the SGP40 sensor
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* @param voc_index Calculated VOC index value from the raw sensor value. Zero
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* during initial blackout period and 1..500 afterwards
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*/
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void VocAlgorithm_process(VocAlgorithmParams* params, int32_t sraw,
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int32_t* voc_index);
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#endif /* VOCALGORITHM_H_ */
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