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+/*
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+ * SPDX-FileCopyrightText: 2022 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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+
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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 "esp_heap_caps.h"
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+#include "esp_efuse_rtc_calib.h"
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+#include "soc/soc_caps.h"
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+#include "esp_adc/adc_cali_scheme.h"
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+#include "adc_cali_interface.h"
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+
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+
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+/**
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+ * This file contains Line Fitting Calibration Scheme for ESP32C2.
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+ *
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+ * If ESP EFuse Line Fitting Calibration Scheme on future chips are similar to the scheme in this file, we can:
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+ *
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+ * 1. Rename this file to `adc_cali_line_fitting_v2.c`, as the Line Fitting Scheme on ESP32 and ESP32S2 are different to this.
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+ * 2. Move this file to common directory
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+ * 3. Still support `ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED`
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+ * 4. Add a new internal maccro `ADC_CALI_SCHEME_LINE_FITTING_V2_SUPPORTED`
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+ * 5. Only build this file, when `ADC_CALI_SCHEME_LINE_FITTING_V2_SUPPORTED == true`
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+ */
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+
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+
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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 = 65536;
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+const static char *TAG = "adc_cali";
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+
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+typedef struct {
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+ adc_unit_t unit_id;
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+ adc_atten_t atten;
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+ uint32_t coeff_a; ///< Gradient of ADC-Voltage characteristics
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+ uint32_t coeff_b; ///< Offset of ADC-Voltage characteristics
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+} cali_chars_line_fitting_t;
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+
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+
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+/* ------------------------ Interface Functions --------------------------- */
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+static esp_err_t cali_raw_to_voltage(void *arg, int raw, int *voltage);
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+static esp_err_t check_valid(const adc_cali_line_fitting_config_t *config);
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+
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+/* ------------------------- Public API ------------------------------------- */
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+esp_err_t adc_cali_create_scheme_line_fitting(const adc_cali_line_fitting_config_t *config, adc_cali_handle_t *ret_handle)
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+{
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+ esp_err_t ret = ESP_OK;
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+ ESP_RETURN_ON_FALSE(config && ret_handle, ESP_ERR_INVALID_ARG, TAG, "invalid arg: null pointer");
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+ ret = check_valid(config);
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+ if (ret != ESP_OK) {
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+ return ret;
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+ }
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+
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+ //current version only accepts encoding version: `ESP_EFUSE_ADC_CALIB_VER`.
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+ uint8_t adc_cali_version = esp_efuse_rtc_calib_get_ver();
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+ ESP_RETURN_ON_FALSE(adc_cali_version == ESP_EFUSE_ADC_CALIB_VER, ESP_ERR_NOT_SUPPORTED, TAG, "Calibration required eFuse bits not burnt");
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+
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+ adc_cali_scheme_t *scheme = (adc_cali_scheme_t *)heap_caps_calloc(1, sizeof(adc_cali_scheme_t), MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
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+ ESP_RETURN_ON_FALSE(scheme, ESP_ERR_NO_MEM, TAG, "no mem for adc calibration scheme");
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+
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+ cali_chars_line_fitting_t *chars = (cali_chars_line_fitting_t *)heap_caps_calloc(1, sizeof(cali_chars_line_fitting_t), MALLOC_CAP_INTERNAL | MALLOC_CAP_8BIT);
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+ ESP_GOTO_ON_FALSE(chars, ESP_ERR_NO_MEM, err, TAG, "no memory for the calibration characteristics");
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+
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+ scheme->raw_to_voltage = cali_raw_to_voltage;
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+ scheme->ctx = chars;
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+
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+ chars->unit_id = config->unit_id;
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+ chars->atten = config->atten;
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+
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+ uint32_t voltage_mv = 0;
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+ uint32_t digi_val = 0;
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+ esp_efuse_rtc_calib_get_cal_voltage(adc_cali_version, chars->unit_id, chars->atten, &digi_val, &voltage_mv);
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+ assert(ret == ESP_OK);
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+ chars->coeff_a = coeff_a_scaling * voltage_mv / digi_val;
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+ chars->coeff_b = 0;
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+ ESP_LOGV(TAG, "Calib V1, Cal Voltage = %"PRId32", Digi out = %"PRId32", Coef_a = %"PRId32"\n", voltage_mv, digi_val, chars->coeff_a);
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+
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+ *ret_handle = scheme;
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+
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+ return ESP_OK;
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+
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+err:
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+ if (scheme) {
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+ free(scheme);
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+ }
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+ return ret;
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+}
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+
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+esp_err_t adc_cali_delete_scheme_line_fitting(adc_cali_handle_t handle)
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+{
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+ ESP_RETURN_ON_FALSE(handle, ESP_ERR_INVALID_ARG, TAG, "invalid argument: null pointer");
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+
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+ free(handle->ctx);
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+ handle->ctx = NULL;
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+
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+ free(handle);
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+ handle = NULL;
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+
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+ return ESP_OK;
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+}
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+
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+
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+/* ------------------------ Interface Functions --------------------------- */
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+static esp_err_t cali_raw_to_voltage(void *arg, int raw, int *voltage)
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+{
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+ //pointers are checked in the upper layer
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+
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+ cali_chars_line_fitting_t *ctx = arg;
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+ *voltage = raw * ctx->coeff_a / coeff_a_scaling + ctx->coeff_b;
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+
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+ return ESP_OK;
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+}
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+
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+static esp_err_t check_valid(const adc_cali_line_fitting_config_t *config)
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+{
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+ ESP_RETURN_ON_FALSE(config->unit_id < SOC_ADC_PERIPH_NUM, ESP_ERR_INVALID_ARG, TAG, "invalid ADC unit");
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+ ESP_RETURN_ON_FALSE((config->atten == ADC_ATTEN_DB_0 || config->atten == ADC_ATTEN_DB_11), ESP_ERR_NOT_SUPPORTED, TAG, "only ADC_ATTEN_DB_0 and ADC_ATTEN_DB_11 are supported");
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+
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+ bool available_oneshot_bitwidth = (config->bitwidth >= SOC_ADC_RTC_MIN_BITWIDTH && config->bitwidth <= SOC_ADC_RTC_MAX_BITWIDTH);
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+ bool available_dma_bitwidth = (config->bitwidth >= SOC_ADC_DIGI_MIN_BITWIDTH && config->bitwidth <= SOC_ADC_DIGI_MAX_BITWIDTH);
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+ bool default_bitwidth_mark = (config->bitwidth == ADC_BITWIDTH_DEFAULT);
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+ bool available_bitwidth = (available_oneshot_bitwidth || available_dma_bitwidth || default_bitwidth_mark);
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+ ESP_RETURN_ON_FALSE(available_bitwidth, ESP_ERR_INVALID_ARG, TAG, "invalid bitwidth");
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+
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+ return ESP_OK;
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+}
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Armando