esp-idf/components/esp_adc_cal/esp_adc_cal_esp32c3.c

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// Copyright 2019-2020 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include "esp_types.h"
#include "esp_err.h"
#include "esp_log.h"
#include "driver/adc.h"
#include "hal/adc_ll.h"
#include "esp_efuse_rtc_calib.h"
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#include "esp_adc_cal.h"
#define ADC_CALIB_CHECK(cond, err_msg, ret) do {\
if (!(cond)) { \
ESP_LOGE(LOG_TAG, err_msg); \
return (ret); \
} \
} while(0)
const static char LOG_TAG[] = "adc_calib";
/* ------------------------ Characterization Constants ---------------------- */
// coeff_a and coeff_b are actually floats
// they are 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;
/* -------------------- Characterization Helper Data Types ------------------ */
typedef struct {
uint32_t voltage;
uint32_t digi;
} adc_calib_data_ver1;
typedef struct {
char version_num;
adc_unit_t adc_num;
adc_atten_t atten_level;
union {
adc_calib_data_ver1 ver1;
} efuse_data;
} adc_calib_parsed_info;
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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)
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{
assert(version_num == 1);
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esp_err_t ret;
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parsed_data_storage->version_num = version_num;
parsed_data_storage->adc_num = adc_num;
parsed_data_storage->atten_level = atten;
// V1 we don't have calibration data for ADC2, using the efuse data of ADC1
uint32_t voltage, digi;
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ret = esp_efuse_rtc_calib_get_cal_voltage(version_num, atten, &digi, &voltage);
if (ret != ESP_OK) {
return ret;
}
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parsed_data_storage->efuse_data.ver1.voltage = voltage;
parsed_data_storage->efuse_data.ver1.digi = digi;
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return ret;
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}
/* ----------------------- Characterization Functions ----------------------- */
/*
* Estimate the (assumed) linear relationship btwn the measured raw value and the voltage
* with the previously done measurement when the chip was manufactured.
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*/
static void calculate_characterization_coefficients(const adc_calib_parsed_info *parsed_data, esp_adc_cal_characteristics_t *chars)
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{
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);
chars->coeff_a = coeff_a_scaling * parsed_data->efuse_data.ver1.voltage / parsed_data->efuse_data.ver1.digi;
chars->coeff_b = 0;
}
/* ------------------------- Public API ------------------------------------- */
esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t source)
{
if (source != ESP_ADC_CAL_VAL_EFUSE_TP) {
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;
}
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)
{
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esp_err_t ret;
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adc_calib_parsed_info 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);
ADC_CALIB_CHECK(bit_width == ADC_WIDTH_BIT_12, "Invalid bit_width", ESP_ADC_CAL_VAL_NOT_SUPPORTED);
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ADC_CALIB_CHECK(atten < 4, "Invalid attenuation", ESP_ADC_CAL_VAL_NOT_SUPPORTED);
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int version_num = esp_efuse_rtc_calib_get_ver();
ADC_CALIB_CHECK(version_num == 1, "No calibration efuse burnt", ESP_ADC_CAL_VAL_NOT_SUPPORTED);
memset(chars, 0, sizeof(esp_adc_cal_characteristics_t));
// make sure adc is calibrated.
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ret = prepare_calib_data_for(version_num, adc_num, atten, &efuse_parsed_data);
if (ret != ESP_OK) {
abort();
}
calculate_characterization_coefficients(&efuse_parsed_data, chars);
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ESP_LOGD(LOG_TAG, "adc%d (atten leven %d) calibration done: A:%d B:%d\n", adc_num, atten, chars->coeff_a, chars->coeff_b);
// Initialize remaining fields
chars->adc_num = adc_num;
chars->atten = atten;
chars->bit_width = bit_width;
// in esp32c3 we only use the two point method to calibrate the adc.
return ESP_ADC_CAL_VAL_EFUSE_TP;
}
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);
return adc_reading * chars->coeff_a / coeff_a_scaling + chars->coeff_b / coeff_b_scaling;
}
esp_err_t esp_adc_cal_get_voltage(adc_channel_t channel,
const esp_adc_cal_characteristics_t *chars,
uint32_t *voltage)
{
// Check parameters
ADC_CALIB_CHECK(chars != NULL, "No characteristic input.", ESP_ERR_INVALID_ARG);
ADC_CALIB_CHECK(voltage != NULL, "No output buffer.", ESP_ERR_INVALID_ARG);
int adc_reading;
if (chars->adc_num == ADC_UNIT_1) {
//Check if channel is valid on ADC1
ADC_CALIB_CHECK((adc1_channel_t)channel < ADC1_CHANNEL_MAX, "Invalid channel", ESP_ERR_INVALID_ARG);
adc_reading = adc1_get_raw(channel);
} else {
//Check if channel is valid on ADC2
ADC_CALIB_CHECK((adc2_channel_t)channel < ADC2_CHANNEL_MAX, "Invalid channel", ESP_ERR_INVALID_ARG);
if (adc2_get_raw(channel, chars->bit_width, &adc_reading) != ESP_OK) {
return ESP_ERR_TIMEOUT; //Timed out waiting for ADC2
}
}
*voltage = esp_adc_cal_raw_to_voltage((uint32_t)adc_reading, chars);
return ESP_OK;
}