esphome/esphome/components/sgp40/sensirion_voc_algorithm.h
2021-06-10 13:04:40 +02:00

147 lines
6.8 KiB
C++

#pragma once
#include <cstdint>
namespace esphome {
namespace sgp40 {
/* The VOC code were originally created by
* https://github.com/Sensirion/embedded-sgp
* The fixed point arithmetic parts of this code were originally created by
* https://github.com/PetteriAimonen/libfixmath
*/
using fix16_t = int32_t;
#define F16(x) ((fix16_t)(((x) >= 0) ? ((x) *65536.0 + 0.5) : ((x) *65536.0 - 0.5)))
static const float VOC_ALGORITHM_SAMPLING_INTERVAL(1.);
static const float VOC_ALGORITHM_INITIAL_BLACKOUT(45.);
static const float VOC_ALGORITHM_VOC_INDEX_GAIN(230.);
static const float VOC_ALGORITHM_SRAW_STD_INITIAL(50.);
static const float VOC_ALGORITHM_SRAW_STD_BONUS(220.);
static const float VOC_ALGORITHM_TAU_MEAN_VARIANCE_HOURS(12.);
static const float VOC_ALGORITHM_TAU_INITIAL_MEAN(20.);
static const float VOC_ALGORITHM_INIT_DURATION_MEAN((3600. * 0.75));
static const float VOC_ALGORITHM_INIT_TRANSITION_MEAN(0.01);
static const float VOC_ALGORITHM_TAU_INITIAL_VARIANCE(2500.);
static const float VOC_ALGORITHM_INIT_DURATION_VARIANCE((3600. * 1.45));
static const float VOC_ALGORITHM_INIT_TRANSITION_VARIANCE(0.01);
static const float VOC_ALGORITHM_GATING_THRESHOLD(340.);
static const float VOC_ALGORITHM_GATING_THRESHOLD_INITIAL(510.);
static const float VOC_ALGORITHM_GATING_THRESHOLD_TRANSITION(0.09);
static const float VOC_ALGORITHM_GATING_MAX_DURATION_MINUTES((60. * 3.));
static const float VOC_ALGORITHM_GATING_MAX_RATIO(0.3);
static const float VOC_ALGORITHM_SIGMOID_L(500.);
static const float VOC_ALGORITHM_SIGMOID_K(-0.0065);
static const float VOC_ALGORITHM_SIGMOID_X0(213.);
static const float VOC_ALGORITHM_VOC_INDEX_OFFSET_DEFAULT(100.);
static const float VOC_ALGORITHM_LP_TAU_FAST(20.0);
static const float VOC_ALGORITHM_LP_TAU_SLOW(500.0);
static const float VOC_ALGORITHM_LP_ALPHA(-0.2);
static const float VOC_ALGORITHM_PERSISTENCE_UPTIME_GAMMA((3. * 3600.));
static const float VOC_ALGORITHM_MEAN_VARIANCE_ESTIMATOR_GAMMA_SCALING(64.);
static const float VOC_ALGORITHM_MEAN_VARIANCE_ESTIMATOR_FI_X16_MAX(32767.);
/**
* Struct to hold all the states of the VOC algorithm.
*/
struct VocAlgorithmParams {
fix16_t mVoc_Index_Offset;
fix16_t mTau_Mean_Variance_Hours;
fix16_t mGating_Max_Duration_Minutes;
fix16_t mSraw_Std_Initial;
fix16_t mUptime;
fix16_t mSraw;
fix16_t mVoc_Index;
fix16_t m_Mean_Variance_Estimator_Gating_Max_Duration_Minutes;
bool m_Mean_Variance_Estimator_Initialized;
fix16_t m_Mean_Variance_Estimator_Mean;
fix16_t m_Mean_Variance_Estimator_Sraw_Offset;
fix16_t m_Mean_Variance_Estimator_Std;
fix16_t m_Mean_Variance_Estimator_Gamma;
fix16_t m_Mean_Variance_Estimator_Gamma_Initial_Mean;
fix16_t m_Mean_Variance_Estimator_Gamma_Initial_Variance;
fix16_t m_Mean_Variance_Estimator_Gamma_Mean;
fix16_t m_Mean_Variance_Estimator_Gamma_Variance;
fix16_t m_Mean_Variance_Estimator_Uptime_Gamma;
fix16_t m_Mean_Variance_Estimator_Uptime_Gating;
fix16_t m_Mean_Variance_Estimator_Gating_Duration_Minutes;
fix16_t m_Mean_Variance_Estimator_Sigmoid_L;
fix16_t m_Mean_Variance_Estimator_Sigmoid_K;
fix16_t m_Mean_Variance_Estimator_Sigmoid_X0;
fix16_t m_Mox_Model_Sraw_Std;
fix16_t m_Mox_Model_Sraw_Mean;
fix16_t m_Sigmoid_Scaled_Offset;
fix16_t m_Adaptive_Lowpass_A1;
fix16_t m_Adaptive_Lowpass_A2;
bool m_Adaptive_Lowpass_Initialized;
fix16_t m_Adaptive_Lowpass_X1;
fix16_t m_Adaptive_Lowpass_X2;
fix16_t m_Adaptive_Lowpass_X3;
};
/**
* Initialize the VOC algorithm parameters. Call this once at the beginning or
* whenever the sensor stopped measurements.
* @param params Pointer to the VocAlgorithmParams struct
*/
void voc_algorithm_init(VocAlgorithmParams *params);
/**
* Get current algorithm states. Retrieved values can be used in
* voc_algorithm_set_states() to resume operation after a short interruption,
* skipping initial learning phase. This feature can only be used after at least
* 3 hours of continuous operation.
* @param params Pointer to the VocAlgorithmParams struct
* @param state0 State0 to be stored
* @param state1 State1 to be stored
*/
void voc_algorithm_get_states(VocAlgorithmParams *params, int32_t *state0, int32_t *state1);
/**
* Set previously retrieved algorithm states to resume operation after a short
* interruption, skipping initial learning phase. This feature should not be
* used after inerruptions of more than 10 minutes. Call this once after
* voc_algorithm_init() and the optional voc_algorithm_set_tuning_parameters(), if
* desired. Otherwise, the algorithm will start with initial learning phase.
* @param params Pointer to the VocAlgorithmParams struct
* @param state0 State0 to be restored
* @param state1 State1 to be restored
*/
void voc_algorithm_set_states(VocAlgorithmParams *params, int32_t state0, int32_t state1);
/**
* Set parameters to customize the VOC algorithm. Call this once after
* voc_algorithm_init(), if desired. Otherwise, the default values will be used.
*
* @param params Pointer to the VocAlgorithmParams struct
* @param voc_index_offset VOC index representing typical (average)
* conditions. Range 1..250, default 100
* @param learning_time_hours Time constant of long-term estimator.
* Past events will be forgotten after about
* twice the learning time.
* Range 1..72 [hours], default 12 [hours]
* @param gating_max_duration_minutes Maximum duration of gating (freeze of
* estimator during high VOC index signal).
* 0 (no gating) or range 1..720 [minutes],
* default 180 [minutes]
* @param std_initial Initial estimate for standard deviation.
* Lower value boosts events during initial
* learning period, but may result in larger
* device-to-device variations.
* Range 10..500, default 50
*/
void voc_algorithm_set_tuning_parameters(VocAlgorithmParams *params, int32_t voc_index_offset,
int32_t learning_time_hours, int32_t gating_max_duration_minutes,
int32_t std_initial);
/**
* Calculate the VOC index value from the raw sensor value.
*
* @param params Pointer to the VocAlgorithmParams struct
* @param sraw Raw value from the SGP40 sensor
* @param voc_index Calculated VOC index value from the raw sensor value. Zero
* during initial blackout period and 1..500 afterwards
*/
void voc_algorithm_process(VocAlgorithmParams *params, int32_t sraw, int32_t *voc_index);
} // namespace sgp40
} // namespace esphome