esp-idf/components/esp_adc/adc_cali_curve_fitting.c

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9.5 KiB
C

/*
* SPDX-FileCopyrightText: 2019-2021 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 "esp_heap_caps.h"
#include "soc/soc_caps.h"
#include "esp_adc/adc_cali_scheme.h"
#include "adc_cali_interface.h"
#include "curve_fitting_coefficients.h"
#if ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED
#include "esp_efuse_rtc_calib.h"
const __attribute__((unused)) static char *TAG = "adc_cali";
// 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 = 65536;
/* -------------------- 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 unit_id;
adc_atten_t atten;
union {
adc_calib_data_ver1_t ver1;
} ref_data;
} adc_calib_info_t;
/* ------------------------ Context Structure--------------------------- */
typedef struct {
uint32_t coeff_a; ///< Gradient of ADC-Voltage curve
uint32_t coeff_b; ///< Offset of ADC-Voltage curve
} cali_chars_first_step_t;
typedef struct {
uint8_t term_num; ///< Term number of the algorithm formula
const uint64_t (*coeff)[COEFF_GROUP_NUM][TERM_MAX][2]; ///< Coeff of each term. See `adc_error_coef_atten` for details (and the magic number 2)
const int32_t (*sign)[COEFF_GROUP_NUM][TERM_MAX]; ///< Sign of each term
} cali_chars_second_step_t;
typedef struct {
adc_unit_t unit_id; ///< ADC unit
adc_atten_t atten; ///< ADC attenuation
cali_chars_first_step_t chars_first_step; ///< Calibration first step characteristics
cali_chars_second_step_t chars_second_step; ///< Calibration second step characteristics
} cali_chars_curve_fitting_t;
/* ----------------------- Characterization Functions ----------------------- */
static void get_first_step_reference_point(int version_num, adc_unit_t unit_id, adc_atten_t atten, adc_calib_info_t *calib_info);
static void calc_first_step_coefficients(const adc_calib_info_t *parsed_data, cali_chars_curve_fitting_t *chars);
static void calc_second_step_coefficients(const adc_cali_curve_fitting_config_t *config, cali_chars_curve_fitting_t *ctx);
static int32_t get_reading_error(uint64_t v_cali_1, const cali_chars_second_step_t *param, adc_atten_t atten);
static esp_err_t check_valid(const adc_cali_curve_fitting_config_t *config);
/* ------------------------ Interface Functions --------------------------- */
static esp_err_t cali_raw_to_voltage(void *arg, int raw, int *voltage);
/* ------------------------- Public API ------------------------------------- */
esp_err_t adc_cali_create_scheme_curve_fitting(const adc_cali_curve_fitting_config_t *config, adc_cali_handle_t *ret_handle)
{
esp_err_t ret = ESP_OK;
ESP_RETURN_ON_FALSE(config && ret_handle, ESP_ERR_INVALID_ARG, TAG, "invalid arg: null pointer");
ret = check_valid(config);
if (ret != ESP_OK) {
return ret;
}
// current version only accepts encoding version: `ESP_EFUSE_ADC_CALIB_VER`.
uint8_t adc_encoding_version = esp_efuse_rtc_calib_get_ver();
ESP_RETURN_ON_FALSE(adc_encoding_version == ESP_EFUSE_ADC_CALIB_VER, ESP_ERR_NOT_SUPPORTED, TAG, "Calibration required eFuse bits not burnt");
adc_cali_scheme_t *scheme = (adc_cali_scheme_t *)heap_caps_calloc(1, sizeof(adc_cali_scheme_t), MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
ESP_RETURN_ON_FALSE(scheme, ESP_ERR_NO_MEM, TAG, "no mem for adc calibration scheme");
cali_chars_curve_fitting_t *chars = (cali_chars_curve_fitting_t *)heap_caps_calloc(1, sizeof(cali_chars_curve_fitting_t), MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
ESP_GOTO_ON_FALSE(chars, ESP_ERR_NO_MEM, err, TAG, "no memory for the calibration characteristics");
scheme->raw_to_voltage = cali_raw_to_voltage;
scheme->ctx = chars;
//Prepare calibration characteristics
adc_calib_info_t calib_info = {0};
//Set first step calibration context
get_first_step_reference_point(adc_encoding_version, config->unit_id, config->atten, &calib_info);
calc_first_step_coefficients(&calib_info, chars);
//Set second step calibration context
calc_second_step_coefficients(config, chars);
chars->unit_id = config->unit_id;
chars->atten = config->atten;
*ret_handle = scheme;
return ESP_OK;
err:
if (scheme) {
free(scheme);
}
return ret;
}
esp_err_t adc_cali_delete_scheme_curve_fitting(adc_cali_handle_t handle)
{
ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid argument: null pointer");
free(handle->ctx);
handle->ctx = NULL;
free(handle);
handle = NULL;
return ESP_OK;
}
/* ------------------------ Interface Functions --------------------------- */
static esp_err_t cali_raw_to_voltage(void *arg, int raw, int *voltage)
{
//pointers are checked in the upper layer
cali_chars_curve_fitting_t *ctx = arg;
uint64_t v_cali_1 = raw * ctx->chars_first_step.coeff_a / coeff_a_scaling + ctx->chars_first_step.coeff_b;
int32_t error = get_reading_error(v_cali_1, &(ctx->chars_second_step), ctx->atten);
*voltage = (int32_t)v_cali_1 - error;
return ESP_OK;
}
/* ----------------------- Characterization Functions ----------------------- */
//To get the reference point (Dout, Vin)
static void get_first_step_reference_point(int version_num, adc_unit_t unit_id, adc_atten_t atten, adc_calib_info_t *calib_info)
{
assert(version_num == ESP_EFUSE_ADC_CALIB_VER);
esp_err_t ret;
calib_info->version_num = version_num;
calib_info->unit_id = unit_id;
calib_info->atten = atten;
uint32_t voltage = 0;
uint32_t digi = 0;
ret = esp_efuse_rtc_calib_get_cal_voltage(version_num, unit_id, atten, &digi, &voltage);
assert(ret == ESP_OK);
calib_info->ref_data.ver1.voltage = voltage;
calib_info->ref_data.ver1.digi = digi;
}
/*
* Estimate the (assumed) linear relationship btwn the measured raw value and the voltage
* with the previously done measurement when the chip was manufactured.
*/
static void calc_first_step_coefficients(const adc_calib_info_t *parsed_data, cali_chars_curve_fitting_t *ctx)
{
ctx->chars_first_step.coeff_a = coeff_a_scaling * parsed_data->ref_data.ver1.voltage / parsed_data->ref_data.ver1.digi;
ctx->chars_first_step.coeff_b = 0;
ESP_LOGV(TAG, "Calib V1, Cal Voltage = %"PRId32", Digi out = %"PRId32", Coef_a = %"PRId32"\n", parsed_data->ref_data.ver1.voltage, parsed_data->ref_data.ver1.digi, ctx->chars_first_step.coeff_a);
}
static void calc_second_step_coefficients(const adc_cali_curve_fitting_config_t *config, cali_chars_curve_fitting_t *ctx)
{
ctx->chars_second_step.term_num = (config->atten == 3) ? 5 : 3;
#if CONFIG_IDF_TARGET_ESP32C3
//On esp32c3, ADC1 and ADC2 share the second step coefficients
ctx->chars_second_step.coeff = &adc1_error_coef_atten;
ctx->chars_second_step.sign = &adc1_error_sign;
#else
ctx->chars_second_step.coeff = (config->unit_id == ADC_UNIT_1) ? &adc1_error_coef_atten : &adc2_error_coef_atten;
ctx->chars_second_step.sign = (config->unit_id == ADC_UNIT_1) ? &adc1_error_sign : &adc2_error_sign;
#endif
}
static int32_t get_reading_error(uint64_t v_cali_1, const cali_chars_second_step_t *param, adc_atten_t atten)
{
if (v_cali_1 == 0) {
return 0;
}
uint8_t term_num = param->term_num;
int32_t error = 0;
uint64_t coeff = 0;
uint64_t variable[term_num];
uint64_t term[term_num];
memset(variable, 0, term_num * sizeof(uint64_t));
memset(term, 0, term_num * sizeof(uint64_t));
/**
* For atten0 ~ 2:
* error = (K0 * X^0) + (K1 * X^1) + (K2 * X^2);
*
* For atten3:
* error = (K0 * X^0) + (K1 * X^1) + (K2 * X^2) + (K3 * X^3) + (K4 * X^4);
*/
variable[0] = 1;
coeff = (*param->coeff)[atten][0][0];
term[0] = variable[0] * coeff / (*param->coeff)[atten][0][1];
error = (int32_t)term[0] * (*param->sign)[atten][0];
for (int i = 1; i < term_num; i++) {
variable[i] = variable[i-1] * v_cali_1;
coeff = (*param->coeff)[atten][i][0];
term[i] = variable[i] * coeff;
ESP_LOGV(TAG, "big coef is %llu, big term%d is %llu, coef_id is %d", coeff, i, term[i], i);
term[i] = term[i] / (*param->coeff)[atten][i][1];
error += (int32_t)term[i] * (*param->sign)[atten][i];
ESP_LOGV(TAG, "term%d is %llu, error is %"PRId32, i, term[i], error);
}
return error;
}
static esp_err_t check_valid(const adc_cali_curve_fitting_config_t *config)
{
ESP_RETURN_ON_FALSE(config->unit_id < SOC_ADC_PERIPH_NUM, ESP_ERR_INVALID_ARG, TAG, "invalid ADC unit");
ESP_RETURN_ON_FALSE(config->atten < SOC_ADC_ATTEN_NUM, ESP_ERR_INVALID_ARG, TAG, "invalid ADC attenuation");
bool available_oneshot_bitwidth = (config->bitwidth >= SOC_ADC_RTC_MIN_BITWIDTH && config->bitwidth <= SOC_ADC_RTC_MAX_BITWIDTH);
bool available_dma_bitwidth = (config->bitwidth >= SOC_ADC_DIGI_MIN_BITWIDTH && config->bitwidth <= SOC_ADC_DIGI_MAX_BITWIDTH);
bool default_bitwidth_mark = (config->bitwidth == ADC_BITWIDTH_DEFAULT);
bool available_bitwidth = (available_oneshot_bitwidth || available_dma_bitwidth || default_bitwidth_mark);
ESP_RETURN_ON_FALSE(available_bitwidth, ESP_ERR_INVALID_ARG, TAG, "invalid bitwidth");
return ESP_OK;
}
#endif //#if ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED