// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD // // 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 // http://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. #ifndef __ESP_ADC_CAL_H__ #define __ESP_ADC_CAL_H__ #ifdef __cplusplus extern "C" { #endif #include #include "esp_err.h" #include "driver/adc.h" /** * @brief Type of calibration value used in characterization */ typedef enum { ESP_ADC_CAL_VAL_EFUSE_VREF = 0, /**< Characterization based on reference voltage stored in eFuse*/ ESP_ADC_CAL_VAL_EFUSE_TP = 1, /**< Characterization based on Two Point values stored in eFuse*/ ESP_ADC_CAL_VAL_DEFAULT_VREF = 2, /**< Characterization based on default reference voltage*/ } esp_adc_cal_value_t; /** * @brief Structure storing characteristics of an ADC * * @note Call esp_adc_cal_characterize() to initialize the structure */ typedef struct { adc_unit_t adc_num; /**< ADC number*/ adc_atten_t atten; /**< ADC attenuation*/ adc_bits_width_t bit_width; /**< ADC bit width */ uint32_t coeff_a; /**< Gradient of ADC-Voltage curve*/ uint32_t coeff_b; /**< Offset of ADC-Voltage curve*/ uint32_t vref; /**< Vref used by lookup table*/ const uint32_t *low_curve; /**< Pointer to low Vref curve of lookup table (NULL if unused)*/ const uint32_t *high_curve; /**< Pointer to high Vref curve of lookup table (NULL if unused)*/ } esp_adc_cal_characteristics_t; /** * @brief Checks if ADC calibration values are burned into eFuse * * This function checks if ADC reference voltage or Two Point values have been * burned to the eFuse of the current ESP32 * * @param value_type Type of calibration value (ESP_ADC_CAL_VAL_EFUSE_VREF or ESP_ADC_CAL_VAL_EFUSE_TP) * * @return * - ESP_OK: The calibration mode is supported in eFuse * - ESP_ERR_NOT_SUPPORTED: Error, eFuse values are not burned * - ESP_ERR_INVALID_ARG: Error, invalid argument (ESP_ADC_CAL_VAL_DEFAULT_VREF) */ esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t value_type); /** * @brief Characterize an ADC at a particular attenuation * * This function will characterize the ADC at a particular attenuation and generate * the ADC-Voltage curve in the form of [y = coeff_a * x + coeff_b]. * Characterization can be based on Two Point values, eFuse Vref, or default Vref * and the calibration values will be prioritized in that order. * * @note Two Point values and eFuse Vref can be enabled/disabled using menuconfig. * * @param[in] adc_num ADC to characterize (ADC_UNIT_1 or ADC_UNIT_2) * @param[in] atten Attenuation to characterize * @param[in] bit_width Bit width configuration of ADC * @param[in] default_vref Default ADC reference voltage in mV (used if eFuse values is not available) * @param[out] chars Pointer to empty structure used to store ADC characteristics * * @return * - ESP_ADC_CAL_VAL_EFUSE_VREF: eFuse Vref used for characterization * - ESP_ADC_CAL_VAL_EFUSE_TP: Two Point value used for characterization (only in Linear Mode) * - ESP_ADC_CAL_VAL_DEFAULT_VREF: Default Vref used for characterization */ esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num, adc_atten_t atten, adc_bits_width_t bit_width, uint32_t default_vref, esp_adc_cal_characteristics_t *chars); /** * @brief Convert an ADC reading to voltage in mV * * This function converts an ADC reading to a voltage in mV based on the ADC's * characteristics. * * @note Characteristics structure must be initialized before this function * is called (call esp_adc_cal_characterize()) * * @param[in] adc_reading ADC reading * @param[in] chars Pointer to initialized structure containing ADC characteristics * * @return Voltage in mV */ uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars); /** * @brief Reads an ADC and converts the reading to a voltage in mV * * This function reads an ADC then converts the raw reading to a voltage in mV * based on the characteristics provided. The ADC that is read is also * determined by the characteristics. * * @note The Characteristics structure must be initialized before this * function is called (call esp_adc_cal_characterize()) * * @param[in] channel ADC Channel to read * @param[in] chars Pointer to initialized ADC characteristics structure * @param[out] voltage Pointer to store converted voltage * * @return * - ESP_OK: ADC read and converted to mV * - ESP_ERR_TIMEOUT: Error, timed out attempting to read ADC * - ESP_ERR_INVALID_ARG: Error due to invalid arguments */ esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel, const esp_adc_cal_characteristics_t *chars, uint32_t *voltage); /* -------------------------- Deprecated API ------------------------------- */ /** @cond */ //Doxygen command to hide deprecated function from API Reference /** * @deprecated ADC1 characterization function. Deprecated in order to accommodate * ADC2 and eFuse functionality. Use esp_adc_cal_characterize() instead */ void esp_adc_cal_get_characteristics(uint32_t vref, adc_atten_t atten, adc_bits_width_t bit_width, esp_adc_cal_characteristics_t *chars) __attribute__((deprecated)); /* * @deprecated This function reads ADC1 and returns the corrected voltage. This * has been deprecated in order to accommodate ADC2 support. Use the * new function esp_adc_cal_get_voltage() instead. */ uint32_t adc1_to_voltage(adc1_channel_t channel, const esp_adc_cal_characteristics_t *chars) __attribute__((deprecated)); /** @endcond */ #ifdef __cplusplus } #endif #endif /* __ESP_ADC_CAL_H__ */