/* * The BSD License (3-clause license) * * Copyright (c) 2017 Gunar Schorcht (https://github.com/gschorcht * All rights reserved. * * 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. */ /* * Driver for Sensirion SHT3x digital temperature and humity sensor * connected to I2C * * Part of esp-open-rtos */ #ifndef DRIVER_SHT3x_H_ #define DRIVER_SHT3x_H_ #include "stdint.h" #include "stdbool.h" #include "FreeRTOS.h" #include "i2c/i2c.h" // Uncomment to enable debug output // #define SHT3x_DEBUG // Change this if you need more than 3 SHT3x sensors #define SHT3x_MAX_SENSORS 3 #ifdef __cplusplus extern "C" { #endif /** * @brief actual or average value set type */ typedef struct { float temperature_c; // temperature in degree Celcius float temperature_f; // temperature in degree Fahrenheit float humidity; // humidity in percent } sht3x_value_set_t; /** * @brief callback unction type to pass result of measurement to user tasks */ typedef void (*sht3x_cb_function_t)(uint32_t sensor, sht3x_value_set_t actual, sht3x_value_set_t average); /** * @brief SHT3x sensor device data structure type */ typedef struct { bool active; uint8_t bus; uint8_t addr; uint32_t period; sht3x_value_set_t actual; sht3x_value_set_t average; bool average_computation; bool average_first_measurement; float average_weight; sht3x_cb_function_t cb_function; TaskHandle_t bg_task; } sht3x_sensor_t; /** * @brief Initialize the SHT3x driver * * This function initializes all internal data structures. It must be called * exactly once at the beginning. * * @return true on success, false on error */ bool sht3x_init (); /** * @brief Initialize a SHT3x sensor * * This function initializes the SHT3x sensor connected to a certain * bus with given slave address and checks its availability. * * Furthermore, it starts a background task for measurements with * the sensor. The background task carries out the measurements periodically * using SHT3x's single shot data acquisition mode with a default period * of 1000 ms. This period be changed using function *set_measurment_period*. * * During each measurement the background task * * 1. determines *actual sensor values* * 2. computes optionally *average sensor values* * 3. calls back optionally a registered function of user task. * * The average value computation uses an exponential moving average * and can be activated (default) or deactivated with function * *sht3x_enable_average_computation*. If the average value computation is * deactivated, *average sensor values* correspond to *actual sensor values*. * The weight (smoothing factor) used in the average value computatoin is 0.2 * by default and can be changed with function *sht3x_set_average_weight*. * * If a callback method has been registered with function * *sht3x_set_callback_function*, it is called after each measurement * to pass measurement results to user tasks. Otherwise, user tasks have to * use function *sht3x_get_values* explicitly to get the results. * * @param bus I2C bus at which SHT3x sensor is connected * @param addr I2C addr of the SHT3x sensor * * @return ID of the sensor (0 or greater on success or -1 on error) */ uint32_t sht3x_create_sensor (uint8_t bus, uint8_t addr); /** * @brief Set the period of the background measurement task for the given * sensor * * Please note: The minimum period is 20 ms since each measurement takes * about 20 ms. * * @param sensor ID of the sensor * @param period Measurement period in ms (default 1000 ms) * * @return true on success, false on error */ bool sht3x_set_measurement_period (uint32_t sensor, uint32_t period); /** * @brief Set the callback function for the background measurement task for * the given sensor * * If a callback method is registered, it is called after each measurement to * pass measurement results to user tasks. Thus, callback function is executed * at the same rate as the measurements. * * @param sensor ID of the sensor * @param function user function called after each measurement * (NULL to delete it for the sensor) * * @return true on success, false on error */ bool sht3x_set_callback_function (uint32_t sensor, sht3x_cb_function_t user_function); /** * @brief Deletes the SHT3x sensor given by its ID * * @param sensor ID of the sensor * * @return true on success, false on error */ bool sht3x_delete_sensor (uint32_t sensor); /** * @brief Get actual and average sensor values * * This function returns the actual and average sensor values of the last * measurement. The parameters *actual* and *average* are pointers to data * structures of the type *sht3x_value_set_t*, which are filled with the * of last measurement. Use NULL for the appropriate parameter if you are * not interested in specific results. * * If average value computation is deactivated, average sensor values * correspond to the actual sensor values. * * Please note: Calling this function is only necessary if no callback * function has been registered for the sensor. * * @param sensor ID of the sensor * @param actual Pointer to a data structure for actual sensor values * @param average Pointer to a data structure for average sensor values * * @return true on success, false on error */ bool sht3x_get_values (uint32_t sensor, sht3x_value_set_t *actual, sht3x_value_set_t *average); /** * @brief Enable (default) or disable average value computation * * In case, the average value computation is disabled, average sensor values * correspond to the actual sensor values. * * @param sensor id of the sensor * @param enabled true to enable or false to disable average computation * * @return true on success, false on error */ bool sht3x_enable_average_computation (uint32_t sensor, bool enabled); /** * @brief Set weight (smoothing factor) for average value computation * * At each measurement carried out by the background task, actual sensor * values are determined. If average value computation is enabled (default), * exponential moving average values are computed according to following * equation * * Average[k] = W * Value + (1-W) * Average [k-1] * * where coefficient W represents the degree of weighting decrease, a constant * smoothing factor between 0 and 1. A higher W discounts older observations * faster. W is 0.2 by default. * * @param sensor id of the sensor * @param weight coefficient W (default is 0.2) * * @return true on success, false on error */ bool sht3x_set_average_weight (uint32_t sensor, float weight); #ifdef __cplusplus } #endif #endif /* DRIVER_SHT3x_H_ */