esp_adc: support adc calibration on esp32c2

components/esp_adc/esp32c2/adc_cali_line_fitting.c

@@ -0,0 +1,133 @@
+/*
+ * SPDX-FileCopyrightText: 2022 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 "esp_efuse_rtc_calib.h"
+#include "soc/soc_caps.h"
+#include "esp_adc/adc_cali_scheme.h"
+#include "adc_cali_interface.h"
+
+
+/**
+ * This file contains Line Fitting Calibration Scheme for ESP32C2.
+ *
+ * If ESP EFuse Line Fitting Calibration Scheme on future chips are similar to the scheme in this file, we can:
+ *
+ * 1. Rename this file to `adc_cali_line_fitting_v2.c`, as the Line Fitting Scheme on ESP32 and ESP32S2 are different to this.
+ * 2. Move this file to common directory
+ * 3. Still support `ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED`
+ * 4. Add a new internal maccro `ADC_CALI_SCHEME_LINE_FITTING_V2_SUPPORTED`
+ * 5. Only build this file, when `ADC_CALI_SCHEME_LINE_FITTING_V2_SUPPORTED == true`
+ */
+
+
+// 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;
+const static char *TAG = "adc_cali";
+
+typedef struct {
+    adc_unit_t unit_id;
+    adc_atten_t atten;
+    uint32_t coeff_a;    ///< Gradient of ADC-Voltage characteristics
+    uint32_t coeff_b;    ///< Offset of ADC-Voltage characteristics
+} cali_chars_line_fitting_t;
+
+
+/* ------------------------ Interface Functions --------------------------- */
+static esp_err_t cali_raw_to_voltage(void *arg, int raw, int *voltage);
+static esp_err_t check_valid(const adc_cali_line_fitting_config_t *config);
+
+/* ------------------------- Public API ------------------------------------- */
+esp_err_t adc_cali_create_scheme_line_fitting(const adc_cali_line_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_cali_version = esp_efuse_rtc_calib_get_ver();
+    ESP_RETURN_ON_FALSE(adc_cali_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_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);
+    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;
+
+    chars->unit_id = config->unit_id;
+    chars->atten = config->atten;
+
+    uint32_t voltage_mv = 0;
+    uint32_t digi_val = 0;
+    esp_efuse_rtc_calib_get_cal_voltage(adc_cali_version, chars->unit_id, chars->atten, &digi_val, &voltage_mv);
+    assert(ret == ESP_OK);
+    chars->coeff_a = coeff_a_scaling * voltage_mv / digi_val;
+    chars->coeff_b = 0;
+    ESP_LOGV(TAG, "Calib V1, Cal Voltage = %"PRId32", Digi out = %"PRId32", Coef_a = %"PRId32"\n", voltage_mv, digi_val, chars->coeff_a);
+
+    *ret_handle = scheme;
+
+    return ESP_OK;
+
+err:
+    if (scheme) {
+        free(scheme);
+    }
+    return ret;
+}
+
+esp_err_t adc_cali_delete_scheme_line_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_line_fitting_t *ctx = arg;
+    *voltage = raw * ctx->coeff_a / coeff_a_scaling + ctx->coeff_b;
+
+    return ESP_OK;
+}
+
+static esp_err_t check_valid(const adc_cali_line_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 == 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");
+
+    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;
+}

components/esp_adc/esp32c2/include/adc_cali_schemes.h

@@ -12,4 +12,4 @@
  * @brief Supported calibration schemes
  */
 
-//No scheme supported
+#define ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED    1