/*
* SPDX-FileCopyrightText: 2020-2021 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include "esp_types.h"
#include "esp_err.h"
#include "esp_log.h"
#include "esp_check.h"
#include "driver/adc.h"
#include "hal/adc_types.h"
#include "esp_efuse_rtc_calib.h"
#include "esp_adc_cal.h"
const static char LOG_TAG[] = "ADC_CALI";
/* ------------------------ Characterization Constants ---------------------- */
//coeff_a is actually a float number
//it is scaled to put them into uint32_t so that the headers do not have to be changed
static const int coeff_a_scaling = 1000000;
/**
* @note Error Calculation
* Coefficients for calculating the reading voltage error.
* Four sets of coefficients for atten0 ~ atten3 respectively.
*
* For each item, first element is the Coefficient, second element is the Multiple. (Coefficient / Multiple) is the real coefficient.
*
* @note {0,0} stands for unused item
* @note In case of the overflow, these coeffcients are recorded as Absolute Value
* @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;
*/
const static uint64_t adc_error_coef_atten[4][10][2] = {
{{9798249589, 1e15}, {50871540569528, 1e16}, {3, 1}, {0, 0}, {0, 0}, //ADC1 atten0
{36615265189, 1e16}, {1353548869615, 1e16}, {3, 1}, {0, 0}, {0, 0}}, //ADC2 atten0
{{101379430548, 1e16}, {49393185868806, 1e16}, {3, 1}, {0, 0}, {0, 0}, //ADC1 atten1
{118964995959, 1e16}, {66319894226185, 1e16}, {2, 1}, {0, 0}, {0, 0}}, //ADC2 atten1
{{208385525314, 1e16}, {147640181047414, 1e16}, {2, 1}, {0, 0}, {0, 0}, //ADC1 atten2
{259011467956, 1e16}, {200996773954387, 1e16}, {1, 1}, {0, 0}, {0, 0}}, //ADC2 atten2
{{13515, 1e15}, {70769718, 1e15}, {1297891447611, 1e16}, {644334888647536, 1e16}, {1,1}, //ADC1 atten3
{15038, 1e15}, {79672528, 1e15}, {1478791187119, 1e16}, {755717904943462, 1e16}, {1,1}} //ADC2 atten3
};
const static int32_t adc_error_sign[4][10] = {
{1, -1, -1, 0, 0, //ADC1 atten0
1, 1, -1, 0, 0}, //ADC2 atten0
{1, -1, -1, 0, 0, //ADC1 atten1
1, -1, -1, 0, 0}, //ADC2 atten1
{1, -1, -1, 0, 0, //ADC1 atten2
1, -1, -1, 0, 0}, //ADC2 atten2
{1, -1, 1, -1, -1, //ADC1 atten3
1, -1, 1, -1, 1} //ADC2 atten3
};
/* -------------------- Characterization Helper Data Types ------------------ */
typedef struct {
uint32_t voltage;
uint32_t digi;
} adc_calib_data_ver1_t;
typedef struct {
char version_num;
adc_unit_t adc_num;
adc_atten_t atten_level;
union {
adc_calib_data_ver1_t ver1;
} ref_data;
} adc_calib_info_t;
//To get the reference point (Dout, Vin)
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)
{
assert(version_num == 1);
esp_err_t ret;
calib_info->version_num = version_num;
calib_info->adc_num = adc_num;
calib_info->atten_level = atten;
uint32_t voltage = 0;
uint32_t digi = 0;
ret = esp_efuse_rtc_calib_get_cal_voltage(version_num, ((adc_num == ADC_UNIT_1) ? 0 : 1), atten, &digi, &voltage);
assert(ret == ESP_OK);
calib_info->ref_data.ver1.voltage = voltage;
calib_info->ref_data.ver1.digi = digi;
return ret;
}
esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
{
if (source != ESP_ADC_CAL_VAL_EFUSE_TP_FIT) {
return ESP_ERR_NOT_SUPPORTED;
}
uint8_t adc_encoding_version = esp_efuse_rtc_calib_get_ver();
if (adc_encoding_version != 1) {
// current version only accepts encoding ver 1.
return ESP_ERR_INVALID_VERSION;
}
return ESP_OK;
}
/*
* Get an expected linear relationship btwn Vin and Dout
*/
static void calculate_characterization_coefficients(const adc_calib_info_t *parsed_data, esp_adc_cal_characteristics_t *chars)
{
chars->coeff_a = coeff_a_scaling * parsed_data->ref_data.ver1.voltage / parsed_data->ref_data.ver1.digi;
chars->coeff_b = 0;
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);
}
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)
{
(void) default_vref;
// Check parameters
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");
ESP_RETURN_ON_FALSE(chars != NULL, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "Ivalid characteristic");
ESP_RETURN_ON_FALSE(atten < ADC_ATTEN_MAX, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "Invalid attenuation");
int version_num = esp_efuse_rtc_calib_get_ver();
ESP_RETURN_ON_FALSE(version_num == 1, ESP_ADC_CAL_VAL_NOT_SUPPORTED, LOG_TAG, "No calibration efuse burnt");
memset(chars, 0, sizeof(esp_adc_cal_characteristics_t));
adc_calib_info_t calib_info = {0};
// make sure adc is calibrated.
get_reference_point(version_num, adc_num, atten, &calib_info);
calculate_characterization_coefficients(&calib_info, chars);
// Initialize remaining fields
chars->adc_num = adc_num;
chars->atten = atten;
chars->bit_width = bit_width;
return ESP_ADC_CAL_VAL_EFUSE_TP_FIT;
}
static int32_t get_reading_error(uint64_t v_cali_1, uint8_t adc_num, uint8_t atten)
{
if (v_cali_1 == 0) {
return 0;
}
uint8_t term_max = (atten == 3) ? 5 : 3;
int32_t error = 0;
uint64_t coeff = 0;
uint64_t term[5] = {0};
/**
* 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;
*/
//Calculate all the power beforehand
term[term_max-1] = 1;
term[term_max-2] = v_cali_1;
for (int term_id = term_max - 3; term_id >= 0; term_id--) {
term[term_id] = term[term_id + 1] * v_cali_1;
}
//Calculate each term
uint8_t coef_id_start = (adc_num == ADC_UNIT_1) ? 0 : 5;
for (int i = 0; i < term_max; i++) {
coeff = adc_error_coef_atten[atten][coef_id_start + i][0];
term[i] = term[i] * coeff;
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);
term[i] = term[i] / adc_error_coef_atten[atten][coef_id_start + i][1];
error += (int32_t)term[i] * adc_error_sign[atten][i];
ESP_LOGV(LOG_TAG, "term%d is %llu, error is %d", i, term[i], error);
}
return error;
}
uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
{
assert(chars != NULL);
//ADC reading won't exceed 4096. Otherwise the raw reading result is wrong, the next calculation will overflow.
assert(adc_reading < 4096);
uint32_t voltage = 0;
int32_t error = 0;
uint64_t v_cali_1 = 0;
//raw * gradient * 1000000
v_cali_1 = adc_reading * chars->coeff_a;
//convert to real number
v_cali_1 = v_cali_1 / coeff_a_scaling;
ESP_LOGV(LOG_TAG, "v_cali_1 is %llu", v_cali_1);
error = get_reading_error(v_cali_1, chars->adc_num, chars->atten);
voltage = (int32_t)v_cali_1 - error;
return voltage;
}
esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel,
const esp_adc_cal_characteristics_t *chars,
uint32_t *voltage)
{
// Check parameters
ESP_RETURN_ON_FALSE(chars != NULL, ESP_ERR_INVALID_ARG, LOG_TAG, "No characteristic input");
ESP_RETURN_ON_FALSE(voltage != NULL, ESP_ERR_INVALID_ARG, LOG_TAG, "No output buffer");
esp_err_t ret = ESP_OK;
int adc_reading;
if (chars->adc_num == ADC_UNIT_1) {
ESP_RETURN_ON_FALSE(channel < SOC_ADC_CHANNEL_NUM(0), ESP_ERR_INVALID_ARG, LOG_TAG, "Invalid channel");
adc_reading = adc1_get_raw(channel);
} else {
ESP_RETURN_ON_FALSE(channel < SOC_ADC_CHANNEL_NUM(1), ESP_ERR_INVALID_ARG, LOG_TAG, "Invalid channel");
ret = adc2_get_raw(channel, chars->bit_width, &adc_reading);
}
*voltage = esp_adc_cal_raw_to_voltage((uint32_t)adc_reading, chars);
return ret;
}