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https://github.com/espressif/esp-idf.git
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217 lines
8.1 KiB
C
217 lines
8.1 KiB
C
/*
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* SPDX-FileCopyrightText: 2020-2021 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stdint.h>
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#include <stdbool.h>
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#include <string.h>
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#include "esp_types.h"
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#include "esp_err.h"
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#include "esp_log.h"
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#include "esp_check.h"
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#include "driver/adc.h"
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#include "hal/adc_types.h"
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#include "esp_efuse_rtc_calib.h"
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#include "esp_adc_cal.h"
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const static char LOG_TAG[] = "ADC_CALI";
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/* ------------------------ Characterization Constants ---------------------- */
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//coeff_a is actually a float number
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//it is scaled to put them into uint32_t so that the headers do not have to be changed
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static const int coeff_a_scaling = 1000000;
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/**
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* @note Error Calculation
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* Coefficients for calculating the reading voltage error.
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* Four sets of coefficients for atten0 ~ atten3 respectively.
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*
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* For each item, first element is the Coefficient, second element is the Multiple. (Coefficient / Multiple) is the real coefficient.
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*
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* @note {0,0} stands for unused item
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* @note In case of the overflow, these coeffcients are recorded as Absolute Value
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* @note For atten0 ~ 2, error = a1 * X^2 + a2 * X + a3; For atten3, error = a1 * X^4 + a2 * X^3 + a3 * X^2 + a4 * X + a5;
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*/
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const static uint64_t adc_error_coef_atten[4][10][2] = {
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{{9798249589, 1e15}, {50871540569528, 1e16}, {3, 1}, {0, 0}, {0, 0}, //ADC1 atten0
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{36615265189, 1e16}, {1353548869615, 1e16}, {3, 1}, {0, 0}, {0, 0}}, //ADC2 atten0
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{{101379430548, 1e16}, {49393185868806, 1e16}, {3, 1}, {0, 0}, {0, 0}, //ADC1 atten1
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{118964995959, 1e16}, {66319894226185, 1e16}, {2, 1}, {0, 0}, {0, 0}}, //ADC2 atten1
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{{208385525314, 1e16}, {147640181047414, 1e16}, {2, 1}, {0, 0}, {0, 0}, //ADC1 atten2
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{259011467956, 1e16}, {200996773954387, 1e16}, {1, 1}, {0, 0}, {0, 0}}, //ADC2 atten2
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{{13515, 1e15}, {70769718, 1e15}, {1297891447611, 1e16}, {644334888647536, 1e16}, {1,1}, //ADC1 atten3
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{15038, 1e15}, {79672528, 1e15}, {1478791187119, 1e16}, {755717904943462, 1e16}, {1,1}} //ADC2 atten3
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};
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const static int32_t adc_error_sign[4][10] = {
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{1, -1, -1, 0, 0, //ADC1 atten0
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1, 1, -1, 0, 0}, //ADC2 atten0
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{1, -1, -1, 0, 0, //ADC1 atten1
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1, -1, -1, 0, 0}, //ADC2 atten1
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{1, -1, -1, 0, 0, //ADC1 atten2
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1, -1, -1, 0, 0}, //ADC2 atten2
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{1, -1, 1, -1, -1, //ADC1 atten3
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1, -1, 1, -1, 1} //ADC2 atten3
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};
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/* -------------------- Characterization Helper Data Types ------------------ */
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typedef struct {
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uint32_t voltage;
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uint32_t digi;
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} adc_calib_data_ver1_t;
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typedef struct {
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char version_num;
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adc_unit_t adc_num;
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adc_atten_t atten_level;
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union {
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adc_calib_data_ver1_t ver1;
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} ref_data;
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} adc_calib_info_t;
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//To get the reference point (Dout, Vin)
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static esp_err_t get_reference_point(int version_num, adc_unit_t adc_num, adc_atten_t atten, adc_calib_info_t *calib_info)
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{
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assert(version_num == 1);
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esp_err_t ret;
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calib_info->version_num = version_num;
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calib_info->adc_num = adc_num;
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calib_info->atten_level = atten;
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uint32_t voltage = 0;
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uint32_t digi = 0;
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ret = esp_efuse_rtc_calib_get_cal_voltage(version_num, ((adc_num == ADC_UNIT_1) ? 0 : 1), atten, &digi, &voltage);
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assert(ret == ESP_OK);
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calib_info->ref_data.ver1.voltage = voltage;
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calib_info->ref_data.ver1.digi = digi;
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return ret;
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}
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esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
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{
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if (source != ESP_ADC_CAL_VAL_EFUSE_TP_FIT) {
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return ESP_ERR_NOT_SUPPORTED;
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}
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uint8_t adc_encoding_version = esp_efuse_rtc_calib_get_ver();
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if (adc_encoding_version != 1) {
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// current version only accepts encoding ver 1.
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return ESP_ERR_INVALID_VERSION;
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}
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return ESP_OK;
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}
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/*
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* Get an expected linear relationship btwn Vin and Dout
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*/
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static void calculate_characterization_coefficients(const adc_calib_info_t *parsed_data, esp_adc_cal_characteristics_t *chars)
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{
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chars->coeff_a = coeff_a_scaling * parsed_data->ref_data.ver1.voltage / parsed_data->ref_data.ver1.digi;
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chars->coeff_b = 0;
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ESP_LOGV(LOG_TAG, "Calib V1, Cal Voltage = %d, Digi out = %d, Coef_a = %d\n", parsed_data->ref_data.ver1.voltage, parsed_data->ref_data.ver1.digi, chars->coeff_a);
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}
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esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
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adc_atten_t atten,
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adc_bits_width_t bit_width,
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uint32_t default_vref,
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esp_adc_cal_characteristics_t *chars)
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{
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(void) default_vref;
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// Check parameters
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ESP_RETURN_ON_FALSE(adc_num == ADC_UNIT_1 || adc_num == ADC_UNIT_2, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "Invalid unit num");
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ESP_RETURN_ON_FALSE(chars != NULL, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "Ivalid characteristic");
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ESP_RETURN_ON_FALSE(atten < ADC_ATTEN_MAX, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "Invalid attenuation");
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int version_num = esp_efuse_rtc_calib_get_ver();
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ESP_RETURN_ON_FALSE(version_num == 1, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "No calibration efuse burnt");
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memset(chars, 0, sizeof(esp_adc_cal_characteristics_t));
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adc_calib_info_t calib_info = {0};
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// make sure adc is calibrated.
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get_reference_point(version_num, adc_num, atten, &calib_info);
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calculate_characterization_coefficients(&calib_info, chars);
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// Initialize remaining fields
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chars->adc_num = adc_num;
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chars->atten = atten;
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chars->bit_width = bit_width;
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return ESP_ADC_CAL_VAL_EFUSE_TP_FIT;
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}
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static int32_t get_reading_error(uint64_t v_cali_1, uint8_t adc_num, uint8_t atten)
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{
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if (v_cali_1 == 0) {
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return 0;
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}
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uint8_t term_max = (atten == 3) ? 5 : 3;
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int32_t error = 0;
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uint64_t coeff = 0;
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uint64_t term[5] = {0};
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/**
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* For atten0 ~ 2:
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* error = a1 * X^2 + a2 * X + a3;
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*
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* For atten3:
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* error = a1 * X^4 + a2 * X^3 + a3 * X^2 + a4 * X + a5;
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*/
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//Calculate all the power beforehand
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term[term_max-1] = 1;
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term[term_max-2] = v_cali_1;
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for (int term_id = term_max - 3; term_id >= 0; term_id--) {
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term[term_id] = term[term_id + 1] * v_cali_1;
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}
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//Calculate each term
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uint8_t coef_id_start = (adc_num == ADC_UNIT_1) ? 0 : 5;
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for (int i = 0; i < term_max; i++) {
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coeff = adc_error_coef_atten[atten][coef_id_start + i][0];
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term[i] = term[i] * coeff;
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ESP_LOGV(LOG_TAG, "big coef is %llu, big term%d is %llu, coef_id is %d", coeff, i, term[i], coef_id_start + i);
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term[i] = term[i] / adc_error_coef_atten[atten][coef_id_start + i][1];
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error += (int32_t)term[i] * adc_error_sign[atten][i];
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ESP_LOGV(LOG_TAG, "term%d is %llu, error is %d", i, term[i], error);
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}
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return error;
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}
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uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
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{
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assert(chars != NULL);
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//ADC reading won't exceed 4096. Otherwise the raw reading result is wrong, the next calculation will overflow.
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assert(adc_reading < 4096);
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uint32_t voltage = 0;
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int32_t error = 0;
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uint64_t v_cali_1 = 0;
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//raw * gradient * 1000000
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v_cali_1 = adc_reading * chars->coeff_a;
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//convert to real number
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v_cali_1 = v_cali_1 / coeff_a_scaling;
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ESP_LOGV(LOG_TAG, "v_cali_1 is %llu", v_cali_1);
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error = get_reading_error(v_cali_1, chars->adc_num, chars->atten);
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voltage = (int32_t)v_cali_1 - error;
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return voltage;
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}
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