adc: upgrade adc calibration algorithm to version 2 on c3

components/esp_adc_cal/CMakeLists.txt

@@ -1,7 +1,7 @@
 idf_build_get_property(target IDF_TARGET)
 
 set(srcs "esp_adc_cal_common.c")
-set(src_target "esp_adc_cal_${target}.c")
+set(src_target "${target}/esp_adc_cal.c")
 if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/${src_target}")
     list(APPEND srcs ${src_target})
 endif()

components/esp_adc_cal/esp32c3/esp_adc_cal.c

@@ -14,6 +14,7 @@
 #include "hal/adc_ll.h"
 #include "esp32c3/esp_efuse_rtc_calib.h"
 #include "esp_adc_cal.h"
+#include "../esp_adc_cal_internal.h"
 
 
 #define ADC_CALIB_CHECK(cond, err_msg, ret) do {\
@@ -28,10 +29,40 @@ const static char LOG_TAG[] = "adc_calib";
 
 /* ------------------------ Characterization Constants ---------------------- */
 
-// coeff_a and coeff_b are actually floats
+// coeff_a is actually a float number
-// they are scaled to put them into uint32_t so that the headers do not have to be changed
+// 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;
-static const int coeff_b_scaling = 1024;
+
+/**
+ * @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 = (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);
+ * @note Above formula is rewritten from the original documentation, please note that the coefficients are re-ordered.
+ * @note ADC1 and ADC2 use same coeffients
+ */
+const static uint64_t adc_error_coef_atten[4][5][2] = {
+                                                        {{225966470500043, 1e15}, {7265418501948, 1e16}, {109410402681, 1e16}, {0, 0}, {0, 0}},                         //atten0
+                                                        {{4229623392600516, 1e16}, {731527490903, 1e16}, {88166562521, 1e16}, {0, 0}, {0, 0}},                          //atten1
+                                                        {{1017859239236435, 1e15}, {97159265299153, 1e16}, {149794028038, 1e16}, {0, 0}, {0, 0}},                       //atten2
+                                                        {{14912262772850453, 1e16}, {228549975564099, 1e16}, {356391935717, 1e16}, {179964582, 1e16}, {42046, 1e16}}    //atten3
+                                                       };
+/**
+ * Term sign
+ * @note ADC1 and ADC2 use same coeffients
+ */
+const static int32_t adc_error_sign[4][5] = {
+                                                {-1, -1, 1,  0,  0}, //atten0
+                                                { 1, -1, 1,  0,  0}, //atten1
+                                                {-1, -1, 1,  0,  0}, //atten2
+                                                {-1, -1, 1, -1,  1}  //atten3
+                                             };
+
 /* -------------------- Characterization Helper Data Types ------------------ */
 typedef struct {
     uint32_t voltage;
@@ -45,9 +76,9 @@ typedef struct {
     union {
         adc_calib_data_ver1 ver1;
     } efuse_data;
-} adc_calib_parsed_info;
+} adc_calib_parsed_info_t;
 
-static esp_err_t prepare_calib_data_for(int version_num, adc_unit_t adc_num, adc_atten_t atten, adc_calib_parsed_info *parsed_data_storage)
+static esp_err_t prepare_calib_data_for(int version_num, adc_unit_t adc_num, adc_atten_t atten, adc_calib_parsed_info_t *parsed_data_storage)
 {
     assert(version_num == 1);
     esp_err_t ret;
@@ -71,7 +102,7 @@ static esp_err_t prepare_calib_data_for(int version_num, adc_unit_t adc_num, adc
  * 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 calculate_characterization_coefficients(const adc_calib_parsed_info *parsed_data, esp_adc_cal_characteristics_t *chars)
+static void calculate_characterization_coefficients(const adc_calib_parsed_info_t *parsed_data, esp_adc_cal_characteristics_t *chars)
 {
     ESP_LOGD(LOG_TAG, "Calib V1, Cal Voltage = %d, Digi out = %d\n", parsed_data->efuse_data.ver1.voltage, parsed_data->efuse_data.ver1.digi);
 
@@ -100,7 +131,7 @@ esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
         esp_adc_cal_characteristics_t *chars)
 {
     esp_err_t ret;
-    adc_calib_parsed_info efuse_parsed_data = {0};
+    adc_calib_parsed_info_t efuse_parsed_data = {0};
     // Check parameters
     ADC_CALIB_CHECK(adc_num == ADC_UNIT_1 || adc_num == ADC_UNIT_2, "Invalid unit num", ESP_ADC_CAL_VAL_NOT_SUPPORTED);
     ADC_CALIB_CHECK(chars != NULL, "Invalid characteristic", ESP_ADC_CAL_VAL_NOT_SUPPORTED);
@@ -132,7 +163,17 @@ esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
 
 uint32_t esp_adc_cal_raw_to_voltage(uint32_t adc_reading, const esp_adc_cal_characteristics_t *chars)
 {
-    ADC_CALIB_CHECK(chars != NULL, "No characteristic input.", ESP_ERR_INVALID_ARG);
+    assert(chars != NULL);
 
-    return adc_reading * chars->coeff_a / coeff_a_scaling + chars->coeff_b / coeff_b_scaling;
+    int32_t error = 0;
+    uint64_t v_cali_1 = adc_reading * chars->coeff_a / coeff_a_scaling;
+    esp_adc_error_calc_param_t param = {
+        .v_cali_input = v_cali_1,
+        .term_num = (chars->atten == 3) ? 5 : 3,
+        .coeff = &adc_error_coef_atten,
+        .sign = &adc_error_sign,
+    };
+    error = esp_adc_cal_get_reading_error(&param, chars->atten);
+
+    return (int32_t)v_cali_1 - error;
 }

components/esp_adc_cal/esp32s2/esp_adc_cal.c

@@ -170,7 +170,6 @@ esp_adc_cal_value_t esp_adc_cal_characterize(adc_unit_t adc_num,
         esp_adc_cal_characteristics_t *chars)
 {
     bool res;
-    bool res __attribute__((unused));
     adc_calib_parsed_info efuse_parsed_data = {0};
     // Check parameters
     assert((adc_num == ADC_UNIT_1) || (adc_num == ADC_UNIT_2));

components/esp_adc_cal/esp_adc_cal_common.c

@@ -12,6 +12,7 @@
 #include "driver/adc.h"
 #include "hal/adc_types.h"
 #include "esp_adc_cal.h"
+#include "esp_adc_cal_internal.h"
 
 #define ADC_CAL_CHECK(cond, ret) ({                                         \
             if(!(cond)){                                                    \
@@ -44,3 +45,49 @@ esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel,
     }
     return ret;
 }
+
+#if ESP_ADC_CAL_CURVE_FITTING_SUPPORTED
+/*------------------------------------------------------------------------------
+ * Private API
+ *----------------------------------------------------------------------------*/
+int32_t esp_adc_cal_get_reading_error(const esp_adc_error_calc_param_t *param, uint8_t atten)
+{
+    if (param->v_cali_input == 0) {
+        return 0;
+    }
+
+    uint64_t v_cali_1 = param->v_cali_input;
+    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 %d", i, term[i], error);
+    }
+
+    return error;
+}
+#endif  //#if ESP_ADC_CAL_CURVE_FITTING_SUPPORTED

components/esp_adc_cal/esp_adc_cal_internal.h

@@ -0,0 +1,50 @@
+/*
+ * SPDX-FileCopyrightText: 2020-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include "sdkconfig.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if CONFIG_IDF_TARGET_ESP32C3 || CONFIG_IDF_TARGET_ESP32S3
+#define ESP_ADC_CAL_CURVE_FITTING_SUPPORTED    1
+
+#define COEFF_GROUP_NUM    4
+#define TERM_MAX           5
+#endif
+
+#if ESP_ADC_CAL_CURVE_FITTING_SUPPORTED
+/**
+ * Calculation parameters used for curve fitting calibration algorithm error
+ *
+ * @note 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);
+ *       Where X is the `v_cali_input`.
+ */
+typedef struct {
+    uint64_t v_cali_input;                                      //Input to calculate the error
+    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
+} esp_adc_error_calc_param_t;
+
+/**
+ * Calculate the curve fitting error
+ *
+ * @param param   see `esp_adc_error_calc_param_t`
+ * @param atten   ADC attenuation
+ */
+int32_t esp_adc_cal_get_reading_error(const esp_adc_error_calc_param_t *param, uint8_t atten);
+
+#endif  //#if ESP_ADC_CAL_CURVE_FITTING_SUPPORTED
+
+
+#ifdef __cplusplus
+}
+#endif

components/esp_adc_cal/include/esp_adc_cal.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */