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Add bh1750, aht20, sgp40 drivers unified on native i2c_master API

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Forked from managed_components (espressif/bh1750, espressif/aht20,
esp-idf-lib/sgp40) and rewrote aht20/sgp40 internals to use
driver/i2c_master.h directly instead of the i2c_bus and i2cdev
wrapper components, so all three sensors share one create/delete
handle pattern over a single i2c_master_bus_handle_t.
This commit is contained in:
Julien Lazarewicz
2026-07-05 23:27:50 +02:00
commit e940c767a6
19 changed files with 2441 additions and 0 deletions
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# espidf_i2c
Forked/rewritten ESP-IDF I2C sensor drivers, unified onto the native
`driver/i2c_master.h` API (ESP-IDF >= 5.3) so every sensor shares the same
handle lifecycle instead of each vendor bringing its own I2C abstraction
(`i2c_bus`, `i2cdev`, etc.).
## Common API convention
Every driver in this repo follows the same shape:
```c
typedef void *xxx_handle_t;
esp_err_t xxx_create(i2c_master_bus_handle_t bus_handle, uint8_t dev_addr, xxx_handle_t *handle_ret);
esp_err_t xxx_delete(xxx_handle_t handle);
// ... device-specific read/measure functions taking xxx_handle_t
```
Callers create one `i2c_master_bus_handle_t` via `i2c_new_master_bus()` and
pass it to each sensor's `_create()`, which internally calls
`i2c_master_bus_add_device()`. No sensor wraps the bus a second time.
## Components
- `bh1750/` — ambient light sensor. Already used the native API upstream;
relocated here unchanged.
- `aht20/` — temperature/humidity sensor. Rewritten from Espressif's
`i2c_bus` component onto `i2c_master_transmit`/`i2c_master_receive`.
- `sgp40/` — VOC index sensor. Rewritten from esp-idf-lib's `i2cdev`
component onto `i2c_master_transmit`/`i2c_master_receive`; the Sensirion
VOC algorithm files are carried over unmodified (no I2C dependency).
## Using from a project
```yaml
dependencies:
laz/bh1750:
git: https://git.jeese.fr/laz/espidf_i2c.git
path: bh1750
laz/aht20:
git: https://git.jeese.fr/laz/espidf_i2c.git
path: aht20
laz/sgp40:
git: https://git.jeese.fr/laz/espidf_i2c.git
path: sgp40
```

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idf_component_register(
SRCS "aht20.c"
INCLUDE_DIRS "include"
PRIV_INCLUDE_DIRS "priv_include"
REQUIRES "esp_driver_i2c"
)

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/*
* SPDX-FileCopyrightText: 2023-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "aht20.h"
#include "esp_log.h"
#include "esp_check.h"
#include "aht20_reg.h"
#define I2C_CLK_SPEED 100000
const static char *TAG = "AHT20";
static esp_err_t aht20_write_reg(aht20_handle_t handle, uint8_t reg_addr, uint8_t *data, uint8_t len)
{
i2c_master_dev_handle_t dev_handle = (i2c_master_dev_handle_t)handle;
uint8_t buf[1 + len];
buf[0] = reg_addr;
memcpy(&buf[1], data, len);
return i2c_master_transmit(dev_handle, buf, sizeof(buf), pdMS_TO_TICKS(1000));
}
static esp_err_t aht20_read_reg(aht20_handle_t handle, uint8_t *data, size_t len)
{
i2c_master_dev_handle_t dev_handle = (i2c_master_dev_handle_t)handle;
return i2c_master_receive(dev_handle, data, len, pdMS_TO_TICKS(1000));
}
static uint8_t aht20_calc_crc(uint8_t *data, uint8_t len)
{
uint8_t i;
uint8_t byte;
uint8_t crc = 0xFF;
for (byte = 0; byte < len; byte++) {
crc ^= data[byte];
for (i = 8; i > 0; --i) {
if ((crc & 0x80) != 0) {
crc = (crc << 1) ^ 0x31;
} else {
crc = crc << 1;
}
}
}
return crc;
}
esp_err_t aht20_read_temperature_humidity(aht20_handle_t handle,
uint32_t *temperature_raw, float *temperature,
uint32_t *humidity_raw, float *humidity)
{
uint8_t status;
uint8_t buf[7];
uint32_t raw_data;
ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid device handle pointer");
buf[0] = 0x33;
buf[1] = 0x00;
ESP_RETURN_ON_ERROR(aht20_write_reg(handle, AHT20_START_MEASURMENT_CMD, buf, 2), TAG, "I2C write error");
vTaskDelay(pdMS_TO_TICKS(100));
ESP_RETURN_ON_ERROR(aht20_read_reg(handle, &status, 1), TAG, "I2C read error");
if ((status & BIT(AT581X_STATUS_Calibration_Enable)) &&
(status & BIT(AT581X_STATUS_CRC_FLAG)) &&
((status & BIT(AT581X_STATUS_BUSY_INDICATION)) == 0)) {
ESP_RETURN_ON_ERROR(aht20_read_reg(handle, buf, 7), TAG, "I2C read error");
ESP_RETURN_ON_ERROR((aht20_calc_crc(buf, 6) != buf[6]), TAG, "crc is error");
raw_data = buf[1];
raw_data = raw_data << 8;
raw_data += buf[2];
raw_data = raw_data << 8;
raw_data += buf[3];
raw_data = raw_data >> 4;
*humidity_raw = raw_data;
*humidity = (float)raw_data * 100 / 1048576;
raw_data = buf[3] & 0x0F;
raw_data = raw_data << 8;
raw_data += buf[4];
raw_data = raw_data << 8;
raw_data += buf[5];
*temperature_raw = raw_data;
*temperature = (float)raw_data * 200 / 1048576 - 50;
return ESP_OK;
} else {
ESP_LOGI(TAG, "data is not ready");
return ESP_ERR_NOT_FINISHED;
}
}
esp_err_t aht20_create(i2c_master_bus_handle_t bus_handle, const uint8_t dev_addr, aht20_handle_t *handle_ret)
{
ESP_LOGI(TAG, "%-15s: %d.%d.%d", CHIP_NAME, AHT20_VER_MAJOR, AHT20_VER_MINOR, AHT20_VER_PATCH);
ESP_LOGI(TAG, "%-15s: %1.1f - %1.1fV", "SUPPLY_VOLTAGE", SUPPLY_VOLTAGE_MIN, SUPPLY_VOLTAGE_MAX);
ESP_LOGI(TAG, "%-15s: %.2f - %.2f degC", "TEMPERATURE", TEMPERATURE_MIN, TEMPERATURE_MAX);
ESP_RETURN_ON_FALSE(bus_handle, ESP_ERR_INVALID_ARG, TAG, "invalid bus handle");
ESP_RETURN_ON_FALSE(handle_ret, ESP_ERR_INVALID_ARG, TAG, "invalid device handle pointer");
const i2c_device_config_t dev_cfg = {
.dev_addr_length = I2C_ADDR_BIT_LEN_7,
.device_address = dev_addr,
.scl_speed_hz = I2C_CLK_SPEED,
};
i2c_master_dev_handle_t dev_handle;
esp_err_t ret = i2c_master_bus_add_device(bus_handle, &dev_cfg, &dev_handle);
if (ret != ESP_OK) {
ESP_LOGE(TAG, "i2c_master_bus_add_device failed");
return ret;
}
*handle_ret = (aht20_handle_t)dev_handle;
return ESP_OK;
}
esp_err_t aht20_delete(aht20_handle_t handle)
{
ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid device handle pointer");
return i2c_master_bus_rm_device((i2c_master_dev_handle_t)handle);
}

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dependencies:
idf: '>=5.3'
description: I2C driver for AHT20 temperature/humidity sensor (native driver/i2c_master.h API)
version: 2.0.0

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/*
* SPDX-FileCopyrightText: 2023-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#pragma once
#ifdef __cplusplus
extern "C" {
#endif
#include "esp_types.h"
#include "esp_err.h"
#include "driver/i2c_master.h"
/* AHT20 address: CE pin low - 0x38, CE pin high - 0x39 */
#define AHT20_ADDRRES_0 (0x38)
#define AHT20_ADDRESS_1 (0x39)
/**
* @brief Type of AHT20 device handle
*/
typedef void *aht20_handle_t;
/**
* @brief Create and init sensor object and return a sensor handle
*
* @param[in] bus_handle I2C bus handle. Obtained from i2c_new_master_bus().
* @param[in] dev_addr I2C address of sensor. Use AHT20_ADDRRES_0 for default address.
* @param[out] handle_ret Handle to created AHT20 driver object.
*
* @return
* - ESP_OK Success
* - ESP_ERR_NO_MEM Not enough memory for the driver
* - Others Error from underlying I2C driver
*/
esp_err_t aht20_create(i2c_master_bus_handle_t bus_handle, const uint8_t dev_addr, aht20_handle_t *handle_ret);
/**
* @brief Delete and release a sensor object
*
* @param sensor object handle of aht20
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t aht20_delete(aht20_handle_t sensor);
/**
* @brief read the temperature and humidity data
*
* @param[in] sensor object handle of aht20
* @param[out] temperature_raw points to a raw temperature buffer
* @param[out] temperature points to a converted temperature buffer
* @param[out] humidity_raw points to a raw humidity buffer
* @param[out] humidity points to a converted humidity buffer
*
* @return
* - ESP_OK Success
* - ESP_ERR_NOT_FINISHED Measurement not ready yet
* - ESP_FAIL Fail
*/
esp_err_t aht20_read_temperature_humidity(aht20_handle_t sensor,
uint32_t *temperature_raw, float *temperature,
uint32_t *humidity_raw, float *humidity);
#ifdef __cplusplus
}
#endif

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/*
* SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#pragma once
/**
* @brief chip information definition
*/
#define CHIP_NAME "ASAIR AHT20" /**< chip name */
#define SUPPLY_VOLTAGE_MIN (2.2f) /**< chip min supply voltage */
#define SUPPLY_VOLTAGE_MAX (5.5f) /**< chip max supply voltage */
#define TEMPERATURE_MIN (-40.0f) /**< chip min operating temperature */
#define TEMPERATURE_MAX (125.0f) /**< chip max operating temperature */
#define AHT20_START_MEASURMENT_CMD 0xAC /* start measurement command */
#define AT581X_STATUS_CMP_INT (2) /* 1 --Out threshold range; 0 --In threshold range */
#define AT581X_STATUS_Calibration_Enable (3) /* 1 --Calibration enable; 0 --Calibration disable */
#define AT581X_STATUS_CRC_FLAG (4) /* 1 --CRC ok; 0 --CRC failed */
#define AT581X_STATUS_MODE_STATUS (5) /* 00 -NOR mode; 01 -CYC mode; 1x --CMD mode */
#define AT581X_STATUS_BUSY_INDICATION (7) /* 1 --Equipment is busy; 0 --Equipment is idle */

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idf_component_register(
SRCS "bh1750.c"
INCLUDE_DIRS "include"
REQUIRES "esp_driver_i2c"
)

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otherwise, or (ii) ownership of fifty percent (50%) or more of the
outstanding shares, or (iii) beneficial ownership of such entity.
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/*
* SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include "bh1750.h"
#include "driver/i2c_master.h"
#include "freertos/FreeRTOS.h"
#include "freertos/projdefs.h" // for pdMS_TO_TICKS
#define BH_1750_MEASUREMENT_ACCURACY \
1.2 /*!< the typical measurement accuracy of BH1750 sensor \
*/
#define BH1750_POWER_DOWN 0x00 /*!< Command to set Power Down*/
#define BH1750_POWER_ON 0x01 /*!< Command to set Power On*/
#define I2C_CLK_SPEED 400000
typedef struct
{
i2c_master_dev_handle_t i2c_handle;
} bh1750_dev_t;
static esp_err_t bh1750_write_byte(const bh1750_dev_t* const sens, const uint8_t byte)
{ return i2c_master_transmit(sens->i2c_handle, &byte, 1, pdMS_TO_TICKS(1000)); }
esp_err_t bh1750_create(i2c_master_bus_handle_t i2c_bus,
const uint8_t dev_addr,
bh1750_handle_t* handle_ret)
{
esp_err_t ret = ESP_OK;
bh1750_dev_t* sensor = (bh1750_dev_t*) calloc(1, sizeof(bh1750_dev_t));
if (!sensor)
{
return ESP_ERR_NO_MEM;
}
// Add new I2C device
const i2c_device_config_t i2c_dev_cfg = {
.device_address = dev_addr,
.scl_speed_hz = I2C_CLK_SPEED,
};
ret = i2c_master_bus_add_device(i2c_bus, &i2c_dev_cfg, &sensor->i2c_handle);
if (ret != ESP_OK)
{
free(sensor);
return ret;
}
assert(sensor->i2c_handle);
*handle_ret = sensor;
return ret;
}
esp_err_t bh1750_delete(bh1750_handle_t sensor)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
if (sens->i2c_handle)
{
i2c_master_bus_rm_device(sens->i2c_handle);
}
free(sens);
return ESP_OK;
}
esp_err_t bh1750_power_down(bh1750_handle_t sensor)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
return bh1750_write_byte(sens, BH1750_POWER_DOWN);
}
esp_err_t bh1750_power_on(bh1750_handle_t sensor)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
return bh1750_write_byte(sens, BH1750_POWER_ON);
}
esp_err_t bh1750_set_measure_time(bh1750_handle_t sensor, const uint8_t measure_time)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
uint32_t i = 0;
uint8_t buf[2] = { 0x40, 0x60 }; // constant part of the the MTreg
buf[0] |= measure_time >> 5;
buf[1] |= measure_time & 0x1F;
for (i = 0; i < 2; i++)
{
esp_err_t ret = bh1750_write_byte(sens, buf[i]);
if (ESP_OK != ret)
{
return ret;
}
}
return ESP_OK;
}
esp_err_t bh1750_set_measure_mode(bh1750_handle_t sensor, const bh1750_measure_mode_t cmd_measure)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
return bh1750_write_byte(sens, (uint8_t) cmd_measure);
}
esp_err_t bh1750_get_data(bh1750_handle_t sensor, float* const data)
{
bh1750_dev_t* sens = (bh1750_dev_t*) sensor;
uint8_t read_buffer[2];
esp_err_t ret = i2c_master_receive(
sens->i2c_handle, read_buffer, sizeof(read_buffer), pdMS_TO_TICKS(1000));
if (ESP_OK != ret)
{
return ret;
}
*data = ((read_buffer[0] << 8 | read_buffer[1]) / BH_1750_MEASUREMENT_ACCURACY);
return ESP_OK;
}

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dependencies:
idf: '>=5.3'
description: I2C driver for BH1750 light sensor (native driver/i2c_master.h API)
version: 2.0.0

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/*
* SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief BH1750 driver
*/
#pragma once
#ifdef __cplusplus
extern "C" {
#endif
#include "driver/i2c_types.h"
#include "esp_err.h"
typedef enum {
BH1750_CONTINUE_1LX_RES = 0x10, /*!< Command to set measure mode as Continuously H-Resolution mode*/
BH1750_CONTINUE_HALFLX_RES = 0x11, /*!< Command to set measure mode as Continuously H-Resolution mode2*/
BH1750_CONTINUE_4LX_RES = 0x13, /*!< Command to set measure mode as Continuously L-Resolution mode*/
BH1750_ONETIME_1LX_RES = 0x20, /*!< Command to set measure mode as One Time H-Resolution mode*/
BH1750_ONETIME_HALFLX_RES = 0x21, /*!< Command to set measure mode as One Time H-Resolution mode2*/
BH1750_ONETIME_4LX_RES = 0x23, /*!< Command to set measure mode as One Time L-Resolution mode*/
} bh1750_measure_mode_t;
#define BH1750_I2C_ADDRESS_DEFAULT (0x23)
typedef void *bh1750_handle_t;
/**
* @brief Set bh1750 as power down mode (low current)
*
* @param sensor object handle of bh1750
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_power_down(bh1750_handle_t sensor);
/**
* @brief Set bh1750 as power on mode
*
* @param sensor object handle of bh1750
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_power_on(bh1750_handle_t sensor);
/**
* @brief Get light intensity from bh1750
*
* @param sensor object handle of bh1750
* @param[in] cmd_measure the instruction to set measurement mode
*
* @note
* You should call this funtion to set measurement mode before call bh1750_get_data() to acquire data.
* If you set onetime mode, you just can get one measurement result.
* If you set continuous mode, you can call bh1750_get_data() to acquire data repeatedly.
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_set_measure_mode(bh1750_handle_t sensor, const bh1750_measure_mode_t cmd_measure);
/**
* @brief Get light intensity from BH1750
*
* Returns light intensity in [lx] corrected by typical BH1750 Measurement Accuracy (= 1.2).
*
* @see BH1750 datasheet Rev. D page 2
*
* @note
* You should acquire data from the sensor after the measurement time is over,
* so take care of measurement time in different modes.
*
* @param sensor object handle of bh1750
* @param[out] data light intensity value got from bh1750 in [lx]
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_get_data(bh1750_handle_t sensor, float *const data);
/**
* @brief Set measurement time
*
* This function is used to adjust BH1750 sensitivity, i.e. compensating influence from optical window.
*
* @see BH1750 datasheet Rev. D page 11
*
* @param sensor object handle of bh1750
* @param[in] measure_time measurement time
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_set_measure_time(bh1750_handle_t sensor, const uint8_t measure_time);
/**
* @brief Create and init sensor object and return a sensor handle
*
* @param[in] i2c_bus I2C bus handle. Obtained from i2c_new_master_bus().s
* @param[in] dev_addr I2C device address of sensor. Use BH1750_I2C_ADDRESS_DEFAULT for default address.
* @param[out] handle_ret Handle to created BH1750 driver object.
*
* @return
* - ESP_OK Success
* - ESP_ERR_NO_MEM Not enough memory for the driver
* - ESP_ERR_NOT_FOUND Sensor not found on the I2C bus
* - Others Error from underlying I2C driver
*/
esp_err_t bh1750_create(i2c_master_bus_handle_t i2c_bus, const uint8_t dev_addr, bh1750_handle_t *handle_ret);
/**
* @brief Delete and release a sensor object
*
* @param sensor object handle of bh1750
*
* @return
* - ESP_OK Success
* - ESP_FAIL Fail
*/
esp_err_t bh1750_delete(bh1750_handle_t sensor);
#ifdef __cplusplus
}
#endif

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idf_component_register(
SRCS "sgp40.c" "sensirion_voc_algorithm.c"
INCLUDE_DIRS "include"
REQUIRES "esp_driver_i2c"
)

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Copyright 2020 Sensirion AG
Copyright 2020 Ruslan V. Uss <unclerus@gmail.com>
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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dependencies:
idf: '>=5.3'
description: I2C driver for SGP40 VOC sensor (native driver/i2c_master.h API)
version: 2.0.0

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/*
* Copyright (c) 2020, Sensirion AG
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of Sensirion AG nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/**
* @file sensirion_voc_algorithm.h
* @defgroup sgp40 sgp40
* @{
*
* Library for calculating concentration of volatile organic compounds
*/
#ifndef VOCALGORITHM_H_
#define VOCALGORITHM_H_
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#ifdef __cplusplus
extern "C" {
#endif
/* The fixed point arithmetic parts of this code were originally created by
* https://github.com/PetteriAimonen/libfixmath
*/
typedef int32_t fix16_t;
#define F16(x) \
((fix16_t)(((x) >= 0) ? ((x)*65536.0 + 0.5) : ((x)*65536.0 - 0.5)))
#define VocAlgorithm_SAMPLING_INTERVAL (1.)
#define VocAlgorithm_INITIAL_BLACKOUT (45.)
#define VocAlgorithm_VOC_INDEX_GAIN (230.)
#define VocAlgorithm_SRAW_STD_INITIAL (50.)
#define VocAlgorithm_SRAW_STD_BONUS (220.)
#define VocAlgorithm_TAU_MEAN_VARIANCE_HOURS (12.)
#define VocAlgorithm_TAU_INITIAL_MEAN (20.)
#define VocAlgorithm_INIT_DURATION_MEAN ((3600. * 0.75))
#define VocAlgorithm_INIT_TRANSITION_MEAN (0.01)
#define VocAlgorithm_TAU_INITIAL_VARIANCE (2500.)
#define VocAlgorithm_INIT_DURATION_VARIANCE ((3600. * 1.45))
#define VocAlgorithm_INIT_TRANSITION_VARIANCE (0.01)
#define VocAlgorithm_GATING_THRESHOLD (340.)
#define VocAlgorithm_GATING_THRESHOLD_INITIAL (510.)
#define VocAlgorithm_GATING_THRESHOLD_TRANSITION (0.09)
#define VocAlgorithm_GATING_MAX_DURATION_MINUTES ((60. * 3.))
#define VocAlgorithm_GATING_MAX_RATIO (0.3)
#define VocAlgorithm_SIGMOID_L (500.)
#define VocAlgorithm_SIGMOID_K (-0.0065)
#define VocAlgorithm_SIGMOID_X0 (213.)
#define VocAlgorithm_VOC_INDEX_OFFSET_DEFAULT (100.)
#define VocAlgorithm_LP_TAU_FAST (20.0)
#define VocAlgorithm_LP_TAU_SLOW (500.0)
#define VocAlgorithm_LP_ALPHA (-0.2)
#define VocAlgorithm_PERSISTENCE_UPTIME_GAMMA ((3. * 3600.))
#define VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING (64.)
#define VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__FIX16_MAX (32767.)
/**
* Struct to hold all the states of the VOC algorithm.
*/
typedef struct
{
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;
} VocAlgorithmParams;
/**
* 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 VocAlgorithm_init(VocAlgorithmParams *params);
/**
* Get current algorithm states. Retrieved values can be used in
* VocAlgorithm_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 VocAlgorithm_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
* VocAlgorithm_init() and the optional VocAlgorithm_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 VocAlgorithm_set_states(VocAlgorithmParams *params, int32_t state0,
int32_t state1);
/**
* Set parameters to customize the VOC algorithm. Call this once after
* VocAlgorithm_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 VocAlgorithm_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 VocAlgorithm_process(VocAlgorithmParams *params, int32_t sraw,
int32_t *voc_index);
#ifdef __cplusplus
}
#endif
/**@}*/
#endif /* VOCALGORITHM_H_ */

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/**
* @file sgp40.h
* @defgroup sgp40 sgp40
* @{
*
* ESP-IDF driver for SGP40 Indoor Air Quality Sensor for VOC Measurements
*
* Copyright (c) 2020 Ruslan V. Uss <unclerus@gmail.com>
*
* BSD Licensed as described in the file LICENSE
*/
#ifndef __SGP40_H__
#define __SGP40_H__
#include <stdbool.h>
#include <esp_err.h>
#include "driver/i2c_master.h"
#include "sensirion_voc_algorithm.h"
#ifdef __cplusplus
extern "C" {
#endif
#define SGP40_ADDR 0x59 //!< I2C address
/**
* @brief Type of SGP40 device handle
*/
typedef void *sgp40_handle_t;
/**
* @brief Create and init sensor object, read device information, initialize the VOC algorithm
*
* @param[in] bus_handle I2C bus handle. Obtained from i2c_new_master_bus().
* @param[in] dev_addr I2C address of sensor. Use SGP40_ADDR for default address.
* @param[out] handle_ret Handle to created SGP40 driver object.
* @return `ESP_OK` on success
*/
esp_err_t sgp40_create(i2c_master_bus_handle_t bus_handle, const uint8_t dev_addr, sgp40_handle_t *handle_ret);
/**
* @brief Delete and release a sensor object
*
* @param sensor object handle of sgp40
* @return `ESP_OK` on success
*/
esp_err_t sgp40_delete(sgp40_handle_t sensor);
/**
* @brief Reset device, than put it to idle mode
*
* @param sensor object handle of sgp40
* @return `ESP_OK` on success
*/
esp_err_t sgp40_soft_reset(sgp40_handle_t sensor);
/**
* @brief Perform a self-test
*
* @param sensor object handle of sgp40
* @return `ESP_OK` on success
*/
esp_err_t sgp40_self_test(sgp40_handle_t sensor);
/**
* @brief Turn hotplate off, stop measurement and put device to idle mode
*
* @param sensor object handle of sgp40
* @return `ESP_OK` on success
*/
esp_err_t sgp40_heater_off(sgp40_handle_t sensor);
/**
* @brief Perform a measurement
*
* @param sensor object handle of sgp40
* @param humidity Relative humidity, percents. Use NaN if
* you want uncompensated measurement
* @param temperature Temperature, degrees Celsius. Use NaN if
* you want uncompensated measurement
* @param[out] raw Raw value, proportional to the logarithm
* of the resistance of the sensing element
* @return `ESP_OK` on success
*/
esp_err_t sgp40_measure_raw(sgp40_handle_t sensor, float humidity, float temperature, uint16_t *raw);
/**
* @brief Perform a measurement and update VOC index
*
* @param sensor object handle of sgp40
* @param humidity Relative humidity, percents. Use NaN if
* you want uncompensated measurement
* @param temperature Temperature, degrees Celsius. Use NaN if
* you want uncompensated measurement
* @param[out] voc_index Calculated VOC index
* @return `ESP_OK` on success
*/
esp_err_t sgp40_measure_voc(sgp40_handle_t sensor, float humidity, float temperature, int32_t *voc_index);
#ifdef __cplusplus
}
#endif
/**@}*/
#endif /* __SGP40_H__ */

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/*
* Copyright (c) 2020, Sensirion AG
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of Sensirion AG nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "sensirion_voc_algorithm.h"
/* The fixed point arithmetic parts of this code were originally created by
* https://github.com/PetteriAimonen/libfixmath
*/
/*!< the maximum value of fix16_t */
#define FIX16_MAXIMUM 0x7FFFFFFF
/*!< the minimum value of fix16_t */
#define FIX16_MINIMUM 0x80000000
/*!< the value used to indicate overflows when FIXMATH_NO_OVERFLOW is not
* specified */
#define FIX16_OVERFLOW 0x80000000
/*!< fix16_t value of 1 */
#define FIX16_ONE 0x00010000
inline fix16_t fix16_from_int(int32_t a)
{
return a * FIX16_ONE;
}
inline int32_t fix16_cast_to_int(fix16_t a)
{
return (a >> 16);
}
/*! Multiplies the two given fix16_t's and returns the result. */
static fix16_t fix16_mul(fix16_t inArg0, fix16_t inArg1);
/*! Divides the first given fix16_t by the second and returns the result. */
static fix16_t fix16_div(fix16_t inArg0, fix16_t inArg1);
/*! Returns the square root of the given fix16_t. */
static fix16_t fix16_sqrt(fix16_t inValue);
/*! Returns the exponent (e^) of the given fix16_t. */
static fix16_t fix16_exp(fix16_t inValue);
static fix16_t fix16_mul(fix16_t inArg0, fix16_t inArg1)
{
// Each argument is divided to 16-bit parts.
// AB
// * CD
// -----------
// BD 16 * 16 -> 32 bit products
// CB
// AD
// AC
// |----| 64 bit product
int32_t A = (inArg0 >> 16), C = (inArg1 >> 16);
uint32_t B = (inArg0 & 0xFFFF), D = (inArg1 & 0xFFFF);
int32_t AC = A * C;
int32_t AD_CB = A * D + C * B;
uint32_t BD = B * D;
int32_t product_hi = AC + (AD_CB >> 16);
// Handle carry from lower 32 bits to upper part of result.
uint32_t ad_cb_temp = AD_CB << 16;
uint32_t product_lo = BD + ad_cb_temp;
if (product_lo < BD)
product_hi++;
#ifndef FIXMATH_NO_OVERFLOW
// The upper 17 bits should all be the same (the sign).
if (product_hi >> 31 != product_hi >> 15)
return FIX16_OVERFLOW;
#endif
#ifdef FIXMATH_NO_ROUNDING
return (product_hi << 16) | (product_lo >> 16);
#else
// Subtracting 0x8000 (= 0.5) and then using signed right shift
// achieves proper rounding to result-1, except in the corner
// case of negative numbers and lowest word = 0x8000.
// To handle that, we also have to subtract 1 for negative numbers.
uint32_t product_lo_tmp = product_lo;
product_lo -= 0x8000;
product_lo -= (uint32_t)product_hi >> 31;
if (product_lo > product_lo_tmp)
product_hi--;
// Discard the lowest 16 bits. Note that this is not exactly the same
// as dividing by 0x10000. For example if product = -1, result will
// also be -1 and not 0. This is compensated by adding +1 to the result
// and compensating this in turn in the rounding above.
fix16_t result = (product_hi << 16) | (product_lo >> 16);
result += 1;
return result;
#endif
}
static fix16_t fix16_div(fix16_t a, fix16_t b)
{
// This uses the basic binary restoring division algorithm.
// It appears to be faster to do the whole division manually than
// trying to compose a 64-bit divide out of 32-bit divisions on
// platforms without hardware divide.
if (b == 0)
return FIX16_MINIMUM;
uint32_t remainder = (a >= 0) ? a : (-a);
uint32_t divider = (b >= 0) ? b : (-b);
uint32_t quotient = 0;
uint32_t bit = 0x10000;
/* The algorithm requires D >= R */
while (divider < remainder)
{
divider <<= 1;
bit <<= 1;
}
#ifndef FIXMATH_NO_OVERFLOW
if (!bit)
return FIX16_OVERFLOW;
#endif
if (divider & 0x80000000)
{
// Perform one step manually to avoid overflows later.
// We know that divider's bottom bit is 0 here.
if (remainder >= divider)
{
quotient |= bit;
remainder -= divider;
}
divider >>= 1;
bit >>= 1;
}
/* Main division loop */
while (bit && remainder)
{
if (remainder >= divider)
{
quotient |= bit;
remainder -= divider;
}
remainder <<= 1;
bit >>= 1;
}
#ifndef FIXMATH_NO_ROUNDING
if (remainder >= divider)
{
quotient++;
}
#endif
fix16_t result = quotient;
/* Figure out the sign of result */
if ((a ^ b) & 0x80000000)
{
#ifndef FIXMATH_NO_OVERFLOW
if (result == FIX16_MINIMUM)
return FIX16_OVERFLOW;
#endif
result = -result;
}
return result;
}
static fix16_t fix16_sqrt(fix16_t x)
{
// It is assumed that x is not negative
uint32_t num = x;
uint32_t result = 0;
uint32_t bit;
uint8_t n;
bit = (uint32_t)1 << 30;
while (bit > num)
bit >>= 2;
// The main part is executed twice, in order to avoid
// using 64 bit values in computations.
for (n = 0; n < 2; n++)
{
// First we get the top 24 bits of the answer.
while (bit)
{
if (num >= result + bit)
{
num -= result + bit;
result = (result >> 1) + bit;
}
else
{
result = (result >> 1);
}
bit >>= 2;
}
if (n == 0)
{
// Then process it again to get the lowest 8 bits.
if (num > 65535)
{
// The remainder 'num' is too large to be shifted left
// by 16, so we have to add 1 to result manually and
// adjust 'num' accordingly.
// num = a - (result + 0.5)^2
// = num + result^2 - (result + 0.5)^2
// = num - result - 0.5
num -= result;
num = (num << 16) - 0x8000;
result = (result << 16) + 0x8000;
}
else
{
num <<= 16;
result <<= 16;
}
bit = 1 << 14;
}
}
#ifndef FIXMATH_NO_ROUNDING
// Finally, if next bit would have been 1, round the result upwards.
if (num > result)
{
result++;
}
#endif
return (fix16_t)result;
}
static fix16_t fix16_exp(fix16_t x)
{
// Function to approximate exp(); optimized more for code size than speed
// exp(x) for x = +/- {1, 1/8, 1/64, 1/512}
#define NUM_EXP_VALUES 4
static const fix16_t exp_pos_values[NUM_EXP_VALUES] =
{
F16(2.7182818), F16(1.1331485), F16(1.0157477), F16(1.0019550)
};
static const fix16_t exp_neg_values[NUM_EXP_VALUES] =
{
F16(0.3678794), F16(0.8824969), F16(0.9844964), F16(0.9980488)
};
const fix16_t* exp_values;
fix16_t res, arg;
uint16_t i;
if (x >= F16(10.3972))
return FIX16_MAXIMUM;
if (x <= F16(-11.7835))
return 0;
if (x < 0)
{
x = -x;
exp_values = exp_neg_values;
}
else
{
exp_values = exp_pos_values;
}
res = FIX16_ONE;
arg = FIX16_ONE;
for (i = 0; i < NUM_EXP_VALUES; i++)
{
while (x >= arg)
{
res = fix16_mul(res, exp_values[i]);
x -= arg;
}
arg >>= 3;
}
return res;
}
static void VocAlgorithm__init_instances(VocAlgorithmParams* params);
static void
VocAlgorithm__mean_variance_estimator__init(VocAlgorithmParams* params);
static void VocAlgorithm__mean_variance_estimator___init_instances(
VocAlgorithmParams* params);
static void VocAlgorithm__mean_variance_estimator__set_parameters(
VocAlgorithmParams* params, fix16_t std_initial,
fix16_t tau_mean_variance_hours, fix16_t gating_max_duration_minutes);
static void
VocAlgorithm__mean_variance_estimator__set_states(VocAlgorithmParams* params,
fix16_t mean, fix16_t std,
fix16_t uptime_gamma);
static fix16_t
VocAlgorithm__mean_variance_estimator__get_std(VocAlgorithmParams* params);
static fix16_t
VocAlgorithm__mean_variance_estimator__get_mean(VocAlgorithmParams* params);
static void VocAlgorithm__mean_variance_estimator___calculate_gamma(
VocAlgorithmParams* params, fix16_t voc_index_from_prior);
static void VocAlgorithm__mean_variance_estimator__process(
VocAlgorithmParams* params, fix16_t sraw, fix16_t voc_index_from_prior);
static void VocAlgorithm__mean_variance_estimator___sigmoid__init(
VocAlgorithmParams* params);
static void VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
VocAlgorithmParams* params, fix16_t L, fix16_t X0, fix16_t K);
static fix16_t VocAlgorithm__mean_variance_estimator___sigmoid__process(
VocAlgorithmParams* params, fix16_t sample);
static void VocAlgorithm__mox_model__init(VocAlgorithmParams* params);
static void VocAlgorithm__mox_model__set_parameters(VocAlgorithmParams* params,
fix16_t SRAW_STD,
fix16_t SRAW_MEAN);
static fix16_t VocAlgorithm__mox_model__process(VocAlgorithmParams* params,
fix16_t sraw);
static void VocAlgorithm__sigmoid_scaled__init(VocAlgorithmParams* params);
static void
VocAlgorithm__sigmoid_scaled__set_parameters(VocAlgorithmParams* params,
fix16_t offset);
static fix16_t VocAlgorithm__sigmoid_scaled__process(VocAlgorithmParams* params,
fix16_t sample);
static void VocAlgorithm__adaptive_lowpass__init(VocAlgorithmParams* params);
static void
VocAlgorithm__adaptive_lowpass__set_parameters(VocAlgorithmParams* params);
static fix16_t
VocAlgorithm__adaptive_lowpass__process(VocAlgorithmParams* params,
fix16_t sample);
void VocAlgorithm_init(VocAlgorithmParams* params)
{
params->mVoc_Index_Offset = F16(VocAlgorithm_VOC_INDEX_OFFSET_DEFAULT);
params->mTau_Mean_Variance_Hours =
F16(VocAlgorithm_TAU_MEAN_VARIANCE_HOURS);
params->mGating_Max_Duration_Minutes =
F16(VocAlgorithm_GATING_MAX_DURATION_MINUTES);
params->mSraw_Std_Initial = F16(VocAlgorithm_SRAW_STD_INITIAL);
params->mUptime = F16(0.);
params->mSraw = F16(0.);
params->mVoc_Index = 0;
VocAlgorithm__init_instances(params);
}
static void VocAlgorithm__init_instances(VocAlgorithmParams* params)
{
VocAlgorithm__mean_variance_estimator__init(params);
VocAlgorithm__mean_variance_estimator__set_parameters(
params, params->mSraw_Std_Initial, params->mTau_Mean_Variance_Hours,
params->mGating_Max_Duration_Minutes);
VocAlgorithm__mox_model__init(params);
VocAlgorithm__mox_model__set_parameters(
params, VocAlgorithm__mean_variance_estimator__get_std(params),
VocAlgorithm__mean_variance_estimator__get_mean(params));
VocAlgorithm__sigmoid_scaled__init(params);
VocAlgorithm__sigmoid_scaled__set_parameters(params,
params->mVoc_Index_Offset);
VocAlgorithm__adaptive_lowpass__init(params);
VocAlgorithm__adaptive_lowpass__set_parameters(params);
}
void VocAlgorithm_get_states(VocAlgorithmParams* params, int32_t* state0,
int32_t* state1)
{
*state0 = VocAlgorithm__mean_variance_estimator__get_mean(params);
*state1 = VocAlgorithm__mean_variance_estimator__get_std(params);
return;
}
void VocAlgorithm_set_states(VocAlgorithmParams* params, int32_t state0,
int32_t state1)
{
VocAlgorithm__mean_variance_estimator__set_states(
params, state0, state1, F16(VocAlgorithm_PERSISTENCE_UPTIME_GAMMA));
params->mSraw = state0;
}
void VocAlgorithm_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)
{
params->mVoc_Index_Offset = (fix16_from_int(voc_index_offset));
params->mTau_Mean_Variance_Hours = (fix16_from_int(learning_time_hours));
params->mGating_Max_Duration_Minutes =
(fix16_from_int(gating_max_duration_minutes));
params->mSraw_Std_Initial = (fix16_from_int(std_initial));
VocAlgorithm__init_instances(params);
}
void VocAlgorithm_process(VocAlgorithmParams* params, int32_t sraw,
int32_t* voc_index)
{
if ((params->mUptime <= F16(VocAlgorithm_INITIAL_BLACKOUT)))
{
params->mUptime =
(params->mUptime + F16(VocAlgorithm_SAMPLING_INTERVAL));
}
else
{
if (((sraw > 0) && (sraw < 65000)))
{
if ((sraw < 20001))
{
sraw = 20001;
}
else if ((sraw > 52767))
{
sraw = 52767;
}
params->mSraw = (fix16_from_int((sraw - 20000)));
}
params->mVoc_Index =
VocAlgorithm__mox_model__process(params, params->mSraw);
params->mVoc_Index =
VocAlgorithm__sigmoid_scaled__process(params, params->mVoc_Index);
params->mVoc_Index =
VocAlgorithm__adaptive_lowpass__process(params, params->mVoc_Index);
if ((params->mVoc_Index < F16(0.5)))
{
params->mVoc_Index = F16(0.5);
}
if ((params->mSraw > F16(0.)))
{
VocAlgorithm__mean_variance_estimator__process(
params, params->mSraw, params->mVoc_Index);
VocAlgorithm__mox_model__set_parameters(
params, VocAlgorithm__mean_variance_estimator__get_std(params),
VocAlgorithm__mean_variance_estimator__get_mean(params));
}
}
*voc_index = (fix16_cast_to_int((params->mVoc_Index + F16(0.5))));
return;
}
static void
VocAlgorithm__mean_variance_estimator__init(VocAlgorithmParams* params)
{
VocAlgorithm__mean_variance_estimator__set_parameters(params, F16(0.),
F16(0.), F16(0.));
VocAlgorithm__mean_variance_estimator___init_instances(params);
}
static void VocAlgorithm__mean_variance_estimator___init_instances(
VocAlgorithmParams* params)
{
VocAlgorithm__mean_variance_estimator___sigmoid__init(params);
}
static void VocAlgorithm__mean_variance_estimator__set_parameters(
VocAlgorithmParams* params, fix16_t std_initial,
fix16_t tau_mean_variance_hours, fix16_t gating_max_duration_minutes)
{
params->m_Mean_Variance_Estimator__Gating_Max_Duration_Minutes =
gating_max_duration_minutes;
params->m_Mean_Variance_Estimator___Initialized = false;
params->m_Mean_Variance_Estimator___Mean = F16(0.);
params->m_Mean_Variance_Estimator___Sraw_Offset = F16(0.);
params->m_Mean_Variance_Estimator___Std = std_initial;
params->m_Mean_Variance_Estimator___Gamma =
(fix16_div(F16((VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING *
(VocAlgorithm_SAMPLING_INTERVAL / 3600.))),
(tau_mean_variance_hours +
F16((VocAlgorithm_SAMPLING_INTERVAL / 3600.)))));
params->m_Mean_Variance_Estimator___Gamma_Initial_Mean =
F16(((VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING *
VocAlgorithm_SAMPLING_INTERVAL) /
(VocAlgorithm_TAU_INITIAL_MEAN + VocAlgorithm_SAMPLING_INTERVAL)));
params->m_Mean_Variance_Estimator___Gamma_Initial_Variance = F16(
((VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING *
VocAlgorithm_SAMPLING_INTERVAL) /
(VocAlgorithm_TAU_INITIAL_VARIANCE + VocAlgorithm_SAMPLING_INTERVAL)));
params->m_Mean_Variance_Estimator__Gamma_Mean = F16(0.);
params->m_Mean_Variance_Estimator__Gamma_Variance = F16(0.);
params->m_Mean_Variance_Estimator___Uptime_Gamma = F16(0.);
params->m_Mean_Variance_Estimator___Uptime_Gating = F16(0.);
params->m_Mean_Variance_Estimator___Gating_Duration_Minutes = F16(0.);
}
static void
VocAlgorithm__mean_variance_estimator__set_states(VocAlgorithmParams* params,
fix16_t mean, fix16_t std,
fix16_t uptime_gamma)
{
params->m_Mean_Variance_Estimator___Mean = mean;
params->m_Mean_Variance_Estimator___Std = std;
params->m_Mean_Variance_Estimator___Uptime_Gamma = uptime_gamma;
params->m_Mean_Variance_Estimator___Initialized = true;
}
static fix16_t
VocAlgorithm__mean_variance_estimator__get_std(VocAlgorithmParams* params)
{
return params->m_Mean_Variance_Estimator___Std;
}
static fix16_t
VocAlgorithm__mean_variance_estimator__get_mean(VocAlgorithmParams* params)
{
return (params->m_Mean_Variance_Estimator___Mean +
params->m_Mean_Variance_Estimator___Sraw_Offset);
}
static void VocAlgorithm__mean_variance_estimator___calculate_gamma(
VocAlgorithmParams* params, fix16_t voc_index_from_prior)
{
fix16_t uptime_limit;
fix16_t sigmoid_gamma_mean;
fix16_t gamma_mean;
fix16_t gating_threshold_mean;
fix16_t sigmoid_gating_mean;
fix16_t sigmoid_gamma_variance;
fix16_t gamma_variance;
fix16_t gating_threshold_variance;
fix16_t sigmoid_gating_variance;
uptime_limit = F16((VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__FIX16_MAX -
VocAlgorithm_SAMPLING_INTERVAL));
if ((params->m_Mean_Variance_Estimator___Uptime_Gamma < uptime_limit))
{
params->m_Mean_Variance_Estimator___Uptime_Gamma =
(params->m_Mean_Variance_Estimator___Uptime_Gamma +
F16(VocAlgorithm_SAMPLING_INTERVAL));
}
if ((params->m_Mean_Variance_Estimator___Uptime_Gating < uptime_limit))
{
params->m_Mean_Variance_Estimator___Uptime_Gating =
(params->m_Mean_Variance_Estimator___Uptime_Gating +
F16(VocAlgorithm_SAMPLING_INTERVAL));
}
VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
params, F16(1.), F16(VocAlgorithm_INIT_DURATION_MEAN),
F16(VocAlgorithm_INIT_TRANSITION_MEAN));
sigmoid_gamma_mean =
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, params->m_Mean_Variance_Estimator___Uptime_Gamma);
gamma_mean =
(params->m_Mean_Variance_Estimator___Gamma +
(fix16_mul((params->m_Mean_Variance_Estimator___Gamma_Initial_Mean -
params->m_Mean_Variance_Estimator___Gamma),
sigmoid_gamma_mean)));
gating_threshold_mean =
(F16(VocAlgorithm_GATING_THRESHOLD) +
(fix16_mul(
F16((VocAlgorithm_GATING_THRESHOLD_INITIAL -
VocAlgorithm_GATING_THRESHOLD)),
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, params->m_Mean_Variance_Estimator___Uptime_Gating))));
VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
params, F16(1.), gating_threshold_mean,
F16(VocAlgorithm_GATING_THRESHOLD_TRANSITION));
sigmoid_gating_mean =
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, voc_index_from_prior);
params->m_Mean_Variance_Estimator__Gamma_Mean =
(fix16_mul(sigmoid_gating_mean, gamma_mean));
VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
params, F16(1.), F16(VocAlgorithm_INIT_DURATION_VARIANCE),
F16(VocAlgorithm_INIT_TRANSITION_VARIANCE));
sigmoid_gamma_variance =
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, params->m_Mean_Variance_Estimator___Uptime_Gamma);
gamma_variance =
(params->m_Mean_Variance_Estimator___Gamma +
(fix16_mul(
(params->m_Mean_Variance_Estimator___Gamma_Initial_Variance -
params->m_Mean_Variance_Estimator___Gamma),
(sigmoid_gamma_variance - sigmoid_gamma_mean))));
gating_threshold_variance =
(F16(VocAlgorithm_GATING_THRESHOLD) +
(fix16_mul(
F16((VocAlgorithm_GATING_THRESHOLD_INITIAL -
VocAlgorithm_GATING_THRESHOLD)),
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, params->m_Mean_Variance_Estimator___Uptime_Gating))));
VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
params, F16(1.), gating_threshold_variance,
F16(VocAlgorithm_GATING_THRESHOLD_TRANSITION));
sigmoid_gating_variance =
VocAlgorithm__mean_variance_estimator___sigmoid__process(
params, voc_index_from_prior);
params->m_Mean_Variance_Estimator__Gamma_Variance =
(fix16_mul(sigmoid_gating_variance, gamma_variance));
params->m_Mean_Variance_Estimator___Gating_Duration_Minutes =
(params->m_Mean_Variance_Estimator___Gating_Duration_Minutes +
(fix16_mul(F16((VocAlgorithm_SAMPLING_INTERVAL / 60.)),
((fix16_mul((F16(1.) - sigmoid_gating_mean),
F16((1. + VocAlgorithm_GATING_MAX_RATIO)))) -
F16(VocAlgorithm_GATING_MAX_RATIO)))));
if ((params->m_Mean_Variance_Estimator___Gating_Duration_Minutes <
F16(0.)))
{
params->m_Mean_Variance_Estimator___Gating_Duration_Minutes = F16(0.);
}
if ((params->m_Mean_Variance_Estimator___Gating_Duration_Minutes >
params->m_Mean_Variance_Estimator__Gating_Max_Duration_Minutes))
{
params->m_Mean_Variance_Estimator___Uptime_Gating = F16(0.);
}
}
static void VocAlgorithm__mean_variance_estimator__process(
VocAlgorithmParams* params, fix16_t sraw, fix16_t voc_index_from_prior)
{
fix16_t delta_sgp;
fix16_t c;
fix16_t additional_scaling;
if ((params->m_Mean_Variance_Estimator___Initialized == false))
{
params->m_Mean_Variance_Estimator___Initialized = true;
params->m_Mean_Variance_Estimator___Sraw_Offset = sraw;
params->m_Mean_Variance_Estimator___Mean = F16(0.);
}
else
{
if (((params->m_Mean_Variance_Estimator___Mean >= F16(100.)) ||
(params->m_Mean_Variance_Estimator___Mean <= F16(-100.))))
{
params->m_Mean_Variance_Estimator___Sraw_Offset =
(params->m_Mean_Variance_Estimator___Sraw_Offset +
params->m_Mean_Variance_Estimator___Mean);
params->m_Mean_Variance_Estimator___Mean = F16(0.);
}
sraw = (sraw - params->m_Mean_Variance_Estimator___Sraw_Offset);
VocAlgorithm__mean_variance_estimator___calculate_gamma(
params, voc_index_from_prior);
delta_sgp = (fix16_div(
(sraw - params->m_Mean_Variance_Estimator___Mean),
F16(VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING)));
if ((delta_sgp < F16(0.)))
{
c = (params->m_Mean_Variance_Estimator___Std - delta_sgp);
}
else
{
c = (params->m_Mean_Variance_Estimator___Std + delta_sgp);
}
additional_scaling = F16(1.);
if ((c > F16(1440.)))
{
additional_scaling = F16(4.);
}
params->m_Mean_Variance_Estimator___Std = (fix16_mul(
fix16_sqrt((fix16_mul(
additional_scaling,
(F16(VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING) -
params->m_Mean_Variance_Estimator__Gamma_Variance)))),
fix16_sqrt((
(fix16_mul(
params->m_Mean_Variance_Estimator___Std,
(fix16_div(
params->m_Mean_Variance_Estimator___Std,
(fix16_mul(
F16(VocAlgorithm_MEAN_VARIANCE_ESTIMATOR__GAMMA_SCALING),
additional_scaling)))))) +
(fix16_mul(
(fix16_div(
(fix16_mul(
params->m_Mean_Variance_Estimator__Gamma_Variance,
delta_sgp)),
additional_scaling)),
delta_sgp))))));
params->m_Mean_Variance_Estimator___Mean =
(params->m_Mean_Variance_Estimator___Mean +
(fix16_mul(params->m_Mean_Variance_Estimator__Gamma_Mean,
delta_sgp)));
}
}
static void VocAlgorithm__mean_variance_estimator___sigmoid__init(
VocAlgorithmParams* params)
{
VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
params, F16(0.), F16(0.), F16(0.));
}
static void VocAlgorithm__mean_variance_estimator___sigmoid__set_parameters(
VocAlgorithmParams* params, fix16_t L, fix16_t X0, fix16_t K)
{
params->m_Mean_Variance_Estimator___Sigmoid__L = L;
params->m_Mean_Variance_Estimator___Sigmoid__K = K;
params->m_Mean_Variance_Estimator___Sigmoid__X0 = X0;
}
static fix16_t VocAlgorithm__mean_variance_estimator___sigmoid__process(
VocAlgorithmParams* params, fix16_t sample)
{
fix16_t x;
x = (fix16_mul(params->m_Mean_Variance_Estimator___Sigmoid__K,
(sample - params->m_Mean_Variance_Estimator___Sigmoid__X0)));
if ((x < F16(-50.)))
{
return params->m_Mean_Variance_Estimator___Sigmoid__L;
}
else if ((x > F16(50.)))
{
return F16(0.);
}
else
{
return (fix16_div(params->m_Mean_Variance_Estimator___Sigmoid__L,
(F16(1.) + fix16_exp(x))));
}
}
static void VocAlgorithm__mox_model__init(VocAlgorithmParams* params)
{
VocAlgorithm__mox_model__set_parameters(params, F16(1.), F16(0.));
}
static void VocAlgorithm__mox_model__set_parameters(VocAlgorithmParams* params,
fix16_t SRAW_STD,
fix16_t SRAW_MEAN)
{
params->m_Mox_Model__Sraw_Std = SRAW_STD;
params->m_Mox_Model__Sraw_Mean = SRAW_MEAN;
}
static fix16_t VocAlgorithm__mox_model__process(VocAlgorithmParams* params,
fix16_t sraw)
{
return (fix16_mul((fix16_div((sraw - params->m_Mox_Model__Sraw_Mean),
(-(params->m_Mox_Model__Sraw_Std +
F16(VocAlgorithm_SRAW_STD_BONUS))))),
F16(VocAlgorithm_VOC_INDEX_GAIN)));
}
static void VocAlgorithm__sigmoid_scaled__init(VocAlgorithmParams* params)
{
VocAlgorithm__sigmoid_scaled__set_parameters(params, F16(0.));
}
static void
VocAlgorithm__sigmoid_scaled__set_parameters(VocAlgorithmParams* params,
fix16_t offset)
{
params->m_Sigmoid_Scaled__Offset = offset;
}
static fix16_t VocAlgorithm__sigmoid_scaled__process(VocAlgorithmParams* params,
fix16_t sample)
{
fix16_t x;
fix16_t shift;
x = (fix16_mul(F16(VocAlgorithm_SIGMOID_K),
(sample - F16(VocAlgorithm_SIGMOID_X0))));
if ((x < F16(-50.)))
{
return F16(VocAlgorithm_SIGMOID_L);
}
else if ((x > F16(50.)))
{
return F16(0.);
}
else
{
if ((sample >= F16(0.)))
{
shift = (fix16_div(
(F16(VocAlgorithm_SIGMOID_L) -
(fix16_mul(F16(5.), params->m_Sigmoid_Scaled__Offset))),
F16(4.)));
return ((fix16_div((F16(VocAlgorithm_SIGMOID_L) + shift),
(F16(1.) + fix16_exp(x)))) -
shift);
}
else
{
return (fix16_mul(
(fix16_div(params->m_Sigmoid_Scaled__Offset,
F16(VocAlgorithm_VOC_INDEX_OFFSET_DEFAULT))),
(fix16_div(F16(VocAlgorithm_SIGMOID_L),
(F16(1.) + fix16_exp(x))))));
}
}
}
static void VocAlgorithm__adaptive_lowpass__init(VocAlgorithmParams* params)
{
VocAlgorithm__adaptive_lowpass__set_parameters(params);
}
static void
VocAlgorithm__adaptive_lowpass__set_parameters(VocAlgorithmParams* params)
{
params->m_Adaptive_Lowpass__A1 =
F16((VocAlgorithm_SAMPLING_INTERVAL /
(VocAlgorithm_LP_TAU_FAST + VocAlgorithm_SAMPLING_INTERVAL)));
params->m_Adaptive_Lowpass__A2 =
F16((VocAlgorithm_SAMPLING_INTERVAL /
(VocAlgorithm_LP_TAU_SLOW + VocAlgorithm_SAMPLING_INTERVAL)));
params->m_Adaptive_Lowpass___Initialized = false;
}
static fix16_t
VocAlgorithm__adaptive_lowpass__process(VocAlgorithmParams* params,
fix16_t sample)
{
fix16_t abs_delta;
fix16_t F1;
fix16_t tau_a;
fix16_t a3;
if ((params->m_Adaptive_Lowpass___Initialized == false))
{
params->m_Adaptive_Lowpass___X1 = sample;
params->m_Adaptive_Lowpass___X2 = sample;
params->m_Adaptive_Lowpass___X3 = sample;
params->m_Adaptive_Lowpass___Initialized = true;
}
params->m_Adaptive_Lowpass___X1 =
((fix16_mul((F16(1.) - params->m_Adaptive_Lowpass__A1),
params->m_Adaptive_Lowpass___X1)) +
(fix16_mul(params->m_Adaptive_Lowpass__A1, sample)));
params->m_Adaptive_Lowpass___X2 =
((fix16_mul((F16(1.) - params->m_Adaptive_Lowpass__A2),
params->m_Adaptive_Lowpass___X2)) +
(fix16_mul(params->m_Adaptive_Lowpass__A2, sample)));
abs_delta =
(params->m_Adaptive_Lowpass___X1 - params->m_Adaptive_Lowpass___X2);
if ((abs_delta < F16(0.)))
{
abs_delta = (-abs_delta);
}
F1 = fix16_exp((fix16_mul(F16(VocAlgorithm_LP_ALPHA), abs_delta)));
tau_a =
((fix16_mul(F16((VocAlgorithm_LP_TAU_SLOW - VocAlgorithm_LP_TAU_FAST)),
F1)) +
F16(VocAlgorithm_LP_TAU_FAST));
a3 = (fix16_div(F16(VocAlgorithm_SAMPLING_INTERVAL),
(F16(VocAlgorithm_SAMPLING_INTERVAL) + tau_a)));
params->m_Adaptive_Lowpass___X3 =
((fix16_mul((F16(1.) - a3), params->m_Adaptive_Lowpass___X3)) +
(fix16_mul(a3, sample)));
return params->m_Adaptive_Lowpass___X3;
}

248
sgp40/sgp40.c Normal file
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@@ -0,0 +1,248 @@
/**
* @file sgp40.c
*
* ESP-IDF driver for SGP40 Indoor Air Quality Sensor for VOC Measurements
*
* Copyright (c) 2020 Ruslan V. Uss <unclerus@gmail.com>
*
* BSD Licensed as described in the file LICENSE
*/
#include <stdlib.h>
#include <math.h>
#include <esp_err.h>
#include <esp_log.h>
#include "sgp40.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#define I2C_FREQ_HZ 400000
static const char *TAG = "sgp40";
#define CMD_SOFT_RESET 0x0006
#define CMD_FEATURESET 0x202f
#define CMD_MEASURE_RAW 0x260f
#define CMD_SELF_TEST 0x280e
#define CMD_SERIAL 0x3682
#define CMD_HEATER_OFF 0x3615
#define TIME_SOFT_RESET 10
#define TIME_FEATURESET 10
#define TIME_MEASURE_RAW 30
#define TIME_SELF_TEST 250
#define TIME_HEATER_OFF 10
#define TIME_SERIAL 10
#define SELF_TEST_OK 0xd400
#define CHECK(x) do { esp_err_t __; if ((__ = x) != ESP_OK) return __; } while (0)
#define CHECK_ARG(ARG) do { if (!(ARG)) return ESP_ERR_INVALID_ARG; } while (0)
typedef struct
{
i2c_master_dev_handle_t i2c_handle;
uint16_t serial[3];
uint16_t featureset;
VocAlgorithmParams voc;
} sgp40_dev_t;
static uint8_t crc8(const uint8_t *data, size_t count)
{
uint8_t res = 0xff;
for (size_t i = 0; i < count; ++i)
{
res ^= data[i];
for (uint8_t bit = 8; bit > 0; --bit)
{
if (res & 0x80)
res = (res << 1) ^ 0x31;
else
res = (res << 1);
}
}
return res;
}
static inline uint16_t swap(uint16_t v)
{
return (v << 8) | (v >> 8);
}
static esp_err_t send_cmd(i2c_master_dev_handle_t dev_handle, uint16_t cmd, uint16_t *data, size_t words)
{
uint8_t buf[2 + words * 3];
// add command
*(uint16_t *)buf = swap(cmd);
if (data && words)
// add arguments
for (size_t i = 0; i < words; i++)
{
uint8_t *p = buf + 2 + i * 3;
*(uint16_t *)p = swap(data[i]);
*(p + 2) = crc8(p, 2);
}
ESP_LOGV(TAG, "Sending buffer:");
ESP_LOG_BUFFER_HEX_LEVEL(TAG, buf, sizeof(buf), ESP_LOG_VERBOSE);
return i2c_master_transmit(dev_handle, buf, sizeof(buf), pdMS_TO_TICKS(1000));
}
static esp_err_t read_resp(i2c_master_dev_handle_t dev_handle, uint16_t *data, size_t words)
{
uint8_t buf[words * 3];
CHECK(i2c_master_receive(dev_handle, buf, sizeof(buf), pdMS_TO_TICKS(1000)));
ESP_LOGV(TAG, "Received buffer:");
ESP_LOG_BUFFER_HEX_LEVEL(TAG, buf, sizeof(buf), ESP_LOG_VERBOSE);
for (size_t i = 0; i < words; i++)
{
uint8_t *p = buf + i * 3;
uint8_t crc = crc8(p, 2);
if (crc != *(p + 2))
{
ESP_LOGE(TAG, "Invalid CRC 0x%02x, expected 0x%02x", crc, *(p + 2));
return ESP_ERR_INVALID_CRC;
}
data[i] = swap(*(uint16_t *)p);
}
return ESP_OK;
}
static esp_err_t execute_cmd(sgp40_dev_t *dev, uint16_t cmd, uint32_t timeout_ms,
uint16_t *out_data, size_t out_words, uint16_t *in_data, size_t in_words)
{
CHECK_ARG(dev);
CHECK(send_cmd(dev->i2c_handle, cmd, out_data, out_words));
if (timeout_ms)
vTaskDelay(pdMS_TO_TICKS(timeout_ms));
if (in_data && in_words)
CHECK(read_resp(dev->i2c_handle, in_data, in_words));
return ESP_OK;
}
////////////////////////////////////////////////////////////////////////////////
esp_err_t sgp40_create(i2c_master_bus_handle_t bus_handle, const uint8_t dev_addr, sgp40_handle_t *handle_ret)
{
CHECK_ARG(bus_handle && handle_ret);
sgp40_dev_t *dev = calloc(1, sizeof(sgp40_dev_t));
if (!dev)
return ESP_ERR_NO_MEM;
const i2c_device_config_t dev_cfg = {
.dev_addr_length = I2C_ADDR_BIT_LEN_7,
.device_address = dev_addr,
.scl_speed_hz = I2C_FREQ_HZ,
};
esp_err_t ret = i2c_master_bus_add_device(bus_handle, &dev_cfg, &dev->i2c_handle);
if (ret != ESP_OK)
{
free(dev);
return ret;
}
ret = execute_cmd(dev, CMD_SERIAL, TIME_SERIAL, NULL, 0, dev->serial, 3);
if (ret == ESP_OK)
ret = execute_cmd(dev, CMD_FEATURESET, TIME_FEATURESET, NULL, 0, &dev->featureset, 1);
if (ret != ESP_OK)
{
i2c_master_bus_rm_device(dev->i2c_handle);
free(dev);
return ret;
}
ESP_LOGD(TAG, "Device found. S/N: 0x%04x%04x%04x, featureset 0x%04x",
dev->serial[0], dev->serial[1], dev->serial[2], dev->featureset);
VocAlgorithm_init(&dev->voc);
*handle_ret = (sgp40_handle_t)dev;
return ESP_OK;
}
esp_err_t sgp40_delete(sgp40_handle_t sensor)
{
CHECK_ARG(sensor);
sgp40_dev_t *dev = (sgp40_dev_t *)sensor;
esp_err_t ret = i2c_master_bus_rm_device(dev->i2c_handle);
free(dev);
return ret;
}
esp_err_t sgp40_soft_reset(sgp40_handle_t sensor)
{
CHECK_ARG(sensor);
return execute_cmd((sgp40_dev_t *)sensor, CMD_SOFT_RESET, TIME_SOFT_RESET, NULL, 0, NULL, 0);
}
esp_err_t sgp40_self_test(sgp40_handle_t sensor)
{
CHECK_ARG(sensor);
uint16_t res;
CHECK(execute_cmd((sgp40_dev_t *)sensor, CMD_SELF_TEST, TIME_SELF_TEST, NULL, 0, &res, 1));
return res == SELF_TEST_OK ? ESP_OK : ESP_FAIL;
}
esp_err_t sgp40_heater_off(sgp40_handle_t sensor)
{
CHECK_ARG(sensor);
return execute_cmd((sgp40_dev_t *)sensor, CMD_HEATER_OFF, TIME_HEATER_OFF, NULL, 0, NULL, 0);
}
esp_err_t sgp40_measure_raw(sgp40_handle_t sensor, float humidity, float temperature, uint16_t *raw)
{
CHECK_ARG(sensor && raw);
uint16_t params[2];
if (isnan(humidity) || isnan(temperature))
{
params[0] = 0x8000;
params[1] = 0x6666;
ESP_LOGW(TAG, "Uncompensated measurement");
}
else
{
if (humidity < 0)
humidity = 0;
else if (humidity > 100)
humidity = 100;
if (temperature < -45)
temperature = -45;
else if (temperature > 129.76)
temperature = 129.76;
params[0] = (uint16_t)(humidity / 100.0 * 65536);
params[1] = (uint16_t)((temperature + 45) / 175.0 * 65535);
}
return execute_cmd((sgp40_dev_t *)sensor, CMD_MEASURE_RAW, TIME_MEASURE_RAW, params, 2, raw, 1);
}
esp_err_t sgp40_measure_voc(sgp40_handle_t sensor, float humidity, float temperature, int32_t *voc_index)
{
CHECK_ARG(sensor && voc_index);
sgp40_dev_t *dev = (sgp40_dev_t *)sensor;
uint16_t raw;
CHECK(sgp40_measure_raw(sensor, humidity, temperature, &raw));
VocAlgorithm_process(&dev->voc, raw, voc_index);
return ESP_OK;
}