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driver/adc: support for esp32s2 adc calibration scheme 

ESP32 lets the user choose from using Vref, Lookup Table, and Two-Point Calibration. In ESP32S2 only two-point calibration is supported. This commit support these changes in idf.

Closes https://github.com/espressif/esp-idf/issues/5455
pull/5778/head
Wu Bo Wen 2020-07-09 20:55:52 +08:00
rodzic 7acda7b8eb
commit 6a0951ecb2
10 zmienionych plików z 393 dodań i 26 usunięć
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2
components/driver/test/CMakeLists.txt
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@ -1,3 +1,3 @@
idf_component_register(SRC_DIRS . param_test touch_sensor_test adc_dma_test dac_dma_test
PRIV_INCLUDE_DIRS include param_test/include touch_sensor_test/include
PRIV_REQUIRES unity test_utils driver nvs_flash esp_serial_slave_link infrared_tools)
PRIV_REQUIRES unity test_utils driver nvs_flash esp_serial_slave_link infrared_tools esp_adc_cal)

58
components/driver/test/test_dac.c
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@ -2,6 +2,7 @@
Tests for the dac device driver
*/
#include "esp_system.h"
#include "driver/adc.h"
#include "driver/dac.h"
#include "unity.h"
@ -13,6 +14,8 @@
#include "test_utils.h"
#include "driver/i2s.h"
#include "esp_adc_cal.h"
static const char *TAG = "test_dac";
#ifdef CONFIG_IDF_TARGET_ESP32
@ -119,3 +122,58 @@ TEST_CASE("DAC cw generator output (RTC) check by adc", "[dac]")
TEST_ESP_OK( dac_cw_generator_disable() );
TEST_ESP_OK( dac_output_disable( DAC_TEST_CHANNEL_NUM ) );
}
#if CONFIG_IDF_TARGET_ESP32S2
static int helper_calc_dac_output(int mV)
{
return mV * 0.07722;
}
static bool subtest_adc_dac(int mV_ref, esp_adc_cal_characteristics_t * chars)
{
dac_output_voltage(DAC_TEST_CHANNEL_NUM, helper_calc_dac_output(mV_ref));
vTaskDelay(pdMS_TO_TICKS(80));
int raw;
adc2_get_raw((adc2_channel_t)ADC_TEST_CHANNEL_NUM, ADC_WIDTH_BIT_13, &raw);
uint32_t voltage = esp_adc_cal_raw_to_voltage(raw, chars);
TEST_ASSERT_INT_WITHIN( 120, mV_ref, voltage ); // 120 mV error allowance, because both DAC and ADC have error
return true;
}
TEST_CASE("esp32s2 adc2-dac with adc2 calibration", "[adc-dac]")
{
gpio_num_t adc_gpio_num, dac_gpio_num;
TEST_ESP_OK( adc2_pad_get_io_num( ADC_TEST_CHANNEL_NUM, &adc_gpio_num ) );
TEST_ESP_OK( dac_pad_get_io_num( DAC_TEST_CHANNEL_NUM, &dac_gpio_num ) );
printf("Please connect ADC2 CH%d-GPIO%d <--> DAC CH%d-GPIO%d.\n", ADC_TEST_CHANNEL_NUM, adc_gpio_num,
DAC_TEST_CHANNEL_NUM + 1, dac_gpio_num );
TEST_ESP_OK( dac_output_enable( DAC_TEST_CHANNEL_NUM ) );
esp_adc_cal_characteristics_t chars;
printf("Test 0dB atten...\n");
adc2_config_channel_atten((adc2_channel_t)ADC_TEST_CHANNEL_NUM, ADC_ATTEN_DB_0);
esp_adc_cal_characterize(ADC_UNIT_2, ADC_ATTEN_DB_0, ADC_WIDTH_BIT_13, 0, &chars);
printf("a %d, b %d\n", chars.coeff_a, chars.coeff_b);
subtest_adc_dac(750, &chars);
printf("Test 2.5dB atten...\n");
adc2_config_channel_atten((adc2_channel_t)ADC_TEST_CHANNEL_NUM, ADC_ATTEN_DB_2_5);
esp_adc_cal_characterize(ADC_UNIT_2, ADC_ATTEN_DB_2_5, ADC_WIDTH_BIT_13, 0, &chars);
printf("a %d, b %d\n", chars.coeff_a, chars.coeff_b);
subtest_adc_dac(1100, &chars);
printf("Test 6dB atten...\n");
adc2_config_channel_atten((adc2_channel_t)ADC_TEST_CHANNEL_NUM, ADC_ATTEN_DB_6);
esp_adc_cal_characterize(ADC_UNIT_2, ADC_ATTEN_DB_6, ADC_WIDTH_BIT_13, 0, &chars);
printf("a %d, b %d\n", chars.coeff_a, chars.coeff_b);
subtest_adc_dac(800, &chars);
subtest_adc_dac(1250, &chars);
printf("Test 11dB atten...\n");
adc2_config_channel_atten((adc2_channel_t)ADC_TEST_CHANNEL_NUM, ADC_ATTEN_DB_11);
esp_adc_cal_characterize(ADC_UNIT_2, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_13, 0, &chars);
printf("a %d, b %d\n", chars.coeff_a, chars.coeff_b);
subtest_adc_dac(1500, &chars);
subtest_adc_dac(2500, &chars);
}
#endif

18
components/esp_adc_cal/CMakeLists.txt
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@ -1,9 +1,15 @@
idf_build_get_property(target IDF_TARGET)
# ToDo: re-enable adc-cal for other target
if(NOT ${target} STREQUAL "esp32")
return()
if(${target} STREQUAL "esp32")
idf_component_register(SRCS "esp_adc_cal_esp32.c"
INCLUDE_DIRS "include"
REQUIRES driver efuse)
elseif(${target} STREQUAL "esp32s2")
idf_component_register(SRCS "esp_adc_cal_esp32s2.c"
INCLUDE_DIRS "include"
REQUIRES driver efuse)
endif()
idf_component_register(SRCS "esp_adc_cal.c"
INCLUDE_DIRS "include"
REQUIRES driver)

4
components/esp_adc_cal/Kconfig
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@ -1,6 +1,7 @@
menu "ADC-Calibration"
config ADC_CAL_EFUSE_TP_ENABLE
depends on IDF_TARGET_ESP32
bool "Use Two Point Values"
default "y"
help
@ -9,6 +10,7 @@ menu "ADC-Calibration"
ADC-Voltage curve using Two Point values if they are available.
config ADC_CAL_EFUSE_VREF_ENABLE
depends on IDF_TARGET_ESP32
bool "Use eFuse Vref"
default "y"
help
@ -17,6 +19,7 @@ menu "ADC-Calibration"
eFuse Vref if it is available.
config ADC_CAL_LUT_ENABLE
depends on IDF_TARGET_ESP32
bool "Use Lookup Tables"
default "y"
help
@ -24,4 +27,5 @@ menu "ADC-Calibration"
to correct for non-linear behavior in 11db attenuation. Other attenuations
do not exhibit non-linear behavior hence will not be affected by this option.
endmenu # ADC-Calibration

4
components/esp_adc_cal/component.mk
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@ -2,4 +2,6 @@
# Component Makefile
#
COMPONENT_ADD_INCLUDEDIRS := include
COMPONENT_ADD_INCLUDEDIRS := include
COMPONENT_OBJEXCLUDE += esp_adc_cal_esp32s2.o

0
components/esp_adc_cal/esp_adc_cal.c → components/esp_adc_cal/esp_adc_cal_esp32.c
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293
components/esp_adc_cal/esp_adc_cal_esp32s2.c 100644
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@ -0,0 +1,293 @@
// 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 "esp_types.h"
#include "driver/adc.h"
#include "soc/efuse_periph.h"
#include "esp_err.h"
#include "assert.h"
#include "esp_adc_cal.h"
#include "esp_efuse.h"
#define ADC_CAL_CHECK(cond, ret) ({ \
if(!(cond)){ \
return ret; \
} \
})
/* ------------------------ Characterization Constants ---------------------- */
#define ADC_CHAR_VERSION1_EFUSEVAL 1
static const uint32_t adc1_D_mean_low[] = {2231, 1643, 1290, 701};
static const uint32_t adc2_D_mean_low[] = {2305, 1693, 1343, 723};
static const uint32_t adc1_D_mean_high[] = {5775, 5692, 5725, 6209};
static const uint32_t adc2_D_mean_high[] = {5817, 5703, 5731, 6157};
static const int Dlow_data_length = 6;
static const int Dhigh_data_length = 8;
static const int adc_efuse_block = 2;
static const int adc_calib_ver_block = 2;
static const int adc_calib_ver_word_loc = 4;
static const int adc_calib_ver_offset = 4;
static const int adc_calib_ver_len = 3;
static const int adc1_atten0_Dlow_word_loc = 6;
static const int adc2_atten0_Dlow_word_loc = 7;
static const int adc1_atten0_Dhigh_word_loc = 4;
static const int adc2_atten0_Dhigh_word_loc = 5;
static const int adc1_atten0_Dlow_offset = 16;
static const int adc2_atten0_Dlow_offset = 8;
static const int adc1_atten0_Dhigh_offset = 16;
static const int adc2_atten0_Dhigh_offset = 16;
/* ----------------------- EFuse Access Functions --------------------------- */
/**
* Convenience function that reads a few bits from efuse and assembles them.
* For example, if the contents of the EFuse are:
* Word2: 0x1234 Word3:0x5678
* Then, setting base=2, offset=24, len=24 will yield 0x456.
* @note does not check for boundaries, make sure parameters are correct
* @param blk EFuse Block
* @param base the starting word
* @param offset the bit offset in the starting word
* @param bit how many consecutive bits to fetch
* @return the assembled number
*/
static uint32_t get_consecutive_bits_from_blk(int blk, uint32_t base, int offset, int len)
{
base += offset / 32;
offset %= 32;
if (offset + len <= 32 || base == 7) {
uint32_t result = esp_efuse_read_reg(blk, base);
result <<= (32 - offset - len);
result >>= (32 - len);
return result;
} else {
// need to fetch both bytes.
uint64_t result = ((uint64_t)esp_efuse_read_reg(blk, base + 1) << 32) + esp_efuse_read_reg(blk, base);
result &= ((uint64_t)1 << (offset + len)) - 1;
result >>= offset;
return result;
}
}
/**
* To save space in EFuse, the calibration values for adc are compressed.
* The compression scheme is: for X bits of ADC Efuse data,
* The actual ADC reading is: BASE_VALUE + 4*ADC_OFFSET
* where ADC_OFFSET = bits X-1:0 in Efuse, the highest bit is the sign bit (0:+, 1:-).
*
* The following functions do this conversion.
* @param efuse_val raw values read from efuse.
* @param adc_num Specifies the channel number. The 2 adc channels each have different calibration values.
* @param attem Specifies the attenuation. Different attenuation level have different calibration values.
*/
static uint32_t efuse_low_val_to_d(uint16_t efuse_val, adc_unit_t adc_num, adc_atten_t atten)
{
// efuse_val is 5 bits + 6th sign bit.
int32_t rawoffsetval = efuse_val & ((1 << (Dlow_data_length - 1)) - 1);
// if the sign bit is 1, it means it is a negative sign.
int32_t offset = (efuse_val & (1 << (Dlow_data_length - 1))) ? (-rawoffsetval * 4) : (rawoffsetval * 4);
if (adc_num == ADC_UNIT_1) {
return offset + adc1_D_mean_low[atten - ADC_ATTEN_DB_0];
} else {
return offset + adc2_D_mean_low[atten - ADC_ATTEN_DB_0];
}
}
static uint32_t efuse_high_val_to_d (uint16_t efuse_val, adc_unit_t adc_num, adc_atten_t atten)
{
// efuse_val is 7 bits + 8th sign bit.
int32_t rawoffsetval = efuse_val & ((1 << (Dhigh_data_length - 1)) - 1);
int32_t offset = (efuse_val & (1 << (Dhigh_data_length - 1))) ? (-rawoffsetval * 4) : (rawoffsetval * 4);
if (adc_num == ADC_UNIT_1) {
return offset + adc1_D_mean_high[atten - ADC_ATTEN_DB_0];
} else {
return offset + adc2_D_mean_high[atten - ADC_ATTEN_DB_0];
}
}
/**
* To save space in EFuse, the calibration values for adc are compressed.
* The compression scheme is: for X bits of ADC Efuse data,
* The actual ADC reading is: BASE_VALUE + 4*ADC_OFFSET
* where ADC_OFFSET = bits X-1:0 in Efuse, the highest bit is the sign bit (0:+, 1:-).
*
* The following functions do the reading.
* @param efuse_val raw values read from efuse.
* @param adc_num Specifies the channel number. The 2 adc channels each have different calibration values.
* @param attem Specifies the attenuation. Different attenuation level have different calibration values.
*/
static uint32_t read_efuse_tp_low(adc_unit_t adc_num, adc_atten_t atten)
{
// this fcn retrieves and decodes the calibration value stored in efuse.
uint32_t base;
int offset;
// may need to move magic numbers out
if (adc_num == ADC_UNIT_1) {
// the first value is at the 16th bit of the 6th word of the efuse block 2, each value is 6 bits long.
base = adc1_atten0_Dlow_word_loc;
offset = adc1_atten0_Dlow_offset + Dlow_data_length * (atten - ADC_ATTEN_DB_0);
} else {
// the first value is at the 8th bit of the 7th word of the efuse block 2, each value is 6 bits long.
base = adc2_atten0_Dlow_word_loc;
offset = adc2_atten0_Dlow_offset + Dlow_data_length * (atten - ADC_ATTEN_DB_0);
}
uint32_t read_result = get_consecutive_bits_from_blk(adc_efuse_block, base, offset, Dlow_data_length);
return read_result;
}
static uint32_t read_efuse_tp_high(adc_unit_t adc_num, adc_atten_t atten)
{
// this fcn retrieves and decodes the calibration value stored in efuse.
uint32_t base;
int offset;
if (adc_num == ADC_UNIT_1) {
// the first value is at the 16th bit of the 4th word of the efuse block 2, each value is 8 bits long.
base = adc1_atten0_Dhigh_word_loc;
offset = adc1_atten0_Dhigh_offset + Dhigh_data_length * (atten - ADC_ATTEN_DB_0);
} else {
// the first value is at the 16th bit of the 5th word of the efuse block 2, each value is 8 bits long.
base = adc2_atten0_Dhigh_word_loc;
offset = adc2_atten0_Dhigh_offset + Dhigh_data_length * (atten - ADC_ATTEN_DB_0);
}
uint32_t read_result = get_consecutive_bits_from_blk(adc_efuse_block, base, offset, Dhigh_data_length);
return read_result;
}
/* ----------------------- Characterization Functions ----------------------- */
// 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;
/**
* The Two Point calibration measures the reading at two specific input voltages, and calculates the (assumed linear) relation
* between input voltage and ADC response. (Response = A * Vinput + B)
* A and B are scaled ints.
* @param high The ADC response at the higher voltage of the corresponding attenuation (600mV, 800mV, 1000mV, 2000mV).
* @param low The ADC response at the lower voltage of the corresponding attenuation (all 250mV).
*
*/
static void characterize_using_two_point(adc_unit_t adc_num,
adc_atten_t atten,
uint32_t high,
uint32_t low,
uint32_t *coeff_a,
uint32_t *coeff_b)
{
// once we have recovered the reference high(Dhigh) and low(Dlow) readings, we can calculate a and b from
// the measured high and low readings
static const uint32_t v_high[] = {600, 800, 1000, 2000};
static const uint32_t v_low = 250;
*coeff_a = coeff_a_scaling * (v_high[atten] - v_low) / (high - low);
*coeff_b = coeff_b_scaling * (v_low * high - v_high[atten] * low) / (high - low);
}
/* ------------------------- 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 adc1_atten0_dh = get_consecutive_bits_from_blk(adc_efuse_block, adc1_atten0_Dhigh_word_loc, adc1_atten0_Dhigh_offset, Dhigh_data_length);
uint8_t adc2_atten0_dh = get_consecutive_bits_from_blk(adc_efuse_block, adc2_atten0_Dhigh_word_loc, adc2_atten0_Dhigh_offset, Dhigh_data_length);
if (!adc1_atten0_dh || !adc2_atten0_dh) {
return ESP_ERR_NOT_SUPPORTED;
}
uint8_t adc_encoding_version = get_consecutive_bits_from_blk(adc_calib_ver_block, adc_calib_ver_word_loc, adc_calib_ver_offset, adc_calib_ver_len);
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)
{
// Check parameters
assert((adc_num == ADC_UNIT_1) || (adc_num == ADC_UNIT_2));
assert(chars != NULL);
assert(bit_width == ADC_WIDTH_BIT_13);
// Characterize based on efuse Two Point values. If these values are not present in efuse,
// or efuse values are of a version that we do not recognize, automatically assume default values.
uint32_t adc_calib_high, adc_calib_low;
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_TP) == ESP_OK) {
adc_calib_high = read_efuse_tp_high(adc_num, atten);
adc_calib_low = read_efuse_tp_low(adc_num, atten);
} else {
adc_calib_high = 0;
adc_calib_low = 0;
}
uint32_t high = efuse_high_val_to_d(adc_calib_high, adc_num, atten);
uint32_t low = efuse_low_val_to_d(adc_calib_low, adc_num, atten);
characterize_using_two_point(adc_num, atten, high, low, &(chars->coeff_a), &(chars->coeff_b));
// Initialize remaining fields
chars->adc_num = adc_num;
chars->atten = atten;
chars->bit_width = bit_width;
// these values are not used as the corresponding calibration themes are deprecated.
chars->vref = 0;
chars->low_curve = NULL;
chars->high_curve = NULL;
// in esp32s2 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_CAL_CHECK(chars != NULL, 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_CAL_CHECK(chars != NULL, ESP_ERR_INVALID_ARG);
ADC_CAL_CHECK(voltage != NULL, ESP_ERR_INVALID_ARG);
int adc_reading;
if (chars->adc_num == ADC_UNIT_1) {
//Check if channel is valid on ADC1
ADC_CAL_CHECK((adc1_channel_t)channel < ADC1_CHANNEL_MAX, ESP_ERR_INVALID_ARG);
adc_reading = adc1_get_raw(channel);
} else {
//Check if channel is valid on ADC2
ADC_CAL_CHECK((adc2_channel_t)channel < ADC2_CHANNEL_MAX, 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;
}

8
components/esp_adc_cal/include/esp_adc_cal.h
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@ -30,6 +30,7 @@ typedef enum {
ESP_ADC_CAL_VAL_EFUSE_VREF = 0, /**< Characterization based on reference voltage stored in eFuse*/
ESP_ADC_CAL_VAL_EFUSE_TP = 1, /**< Characterization based on Two Point values stored in eFuse*/
ESP_ADC_CAL_VAL_DEFAULT_VREF = 2, /**< Characterization based on default reference voltage*/
ESP_ADC_CAL_VAL_MAX
} esp_adc_cal_value_t;
/**
@ -71,12 +72,15 @@ esp_err_t esp_adc_cal_check_efuse(esp_adc_cal_value_t value_type);
* Characterization can be based on Two Point values, eFuse Vref, or default Vref
* and the calibration values will be prioritized in that order.
*
* @note Two Point values and eFuse Vref can be enabled/disabled using menuconfig.
* @note
* For ESP32, Two Point values and eFuse Vref calibration can be enabled/disabled using menuconfig.
* For ESP32s2, only Two Point values calibration and only ADC_WIDTH_BIT_13 is supported. The parameter default_vref is unused.
*
*
* @param[in] adc_num ADC to characterize (ADC_UNIT_1 or ADC_UNIT_2)
* @param[in] atten Attenuation to characterize
* @param[in] bit_width Bit width configuration of ADC
* @param[in] default_vref Default ADC reference voltage in mV (used if eFuse values is not available)
* @param[in] default_vref Default ADC reference voltage in mV (Only in ESP32, used if eFuse values is not available)
* @param[out] chars Pointer to empty structure used to store ADC characteristics
*
* @return

30
examples/peripherals/adc/main/adc1_example_main.c
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@ -12,15 +12,13 @@
#include "freertos/task.h"
#include "driver/gpio.h"
#include "driver/adc.h"
#if CONFIG_IDF_TARGET_ESP32
#include "esp_adc_cal.h"
#endif
#define DEFAULT_VREF 1100 //Use adc2_vref_to_gpio() to obtain a better estimate
#define NO_OF_SAMPLES 64 //Multisampling
#if CONFIG_IDF_TARGET_ESP32
static esp_adc_cal_characteristics_t *adc_chars;
#if CONFIG_IDF_TARGET_ESP32
static const adc_channel_t channel = ADC_CHANNEL_6; //GPIO34 if ADC1, GPIO14 if ADC2
static const adc_bits_width_t width = ADC_WIDTH_BIT_12;
#elif CONFIG_IDF_TARGET_ESP32S2
@ -30,24 +28,34 @@ static const adc_bits_width_t width = ADC_WIDTH_BIT_13;
static const adc_atten_t atten = ADC_ATTEN_DB_0;
static const adc_unit_t unit = ADC_UNIT_1;
#if CONFIG_IDF_TARGET_ESP32
static void check_efuse(void)
{
//Check TP is burned into eFuse
#if CONFIG_IDF_TARGET_ESP32
//Check if TP is burned into eFuse
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_TP) == ESP_OK) {
printf("eFuse Two Point: Supported\n");
} else {
printf("eFuse Two Point: NOT supported\n");
}
//Check Vref is burned into eFuse
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_VREF) == ESP_OK) {
printf("eFuse Vref: Supported\n");
} else {
printf("eFuse Vref: NOT supported\n");
}
#elif CONFIG_IDF_TARGET_ESP32S2
if (esp_adc_cal_check_efuse(ESP_ADC_CAL_VAL_EFUSE_TP) == ESP_OK) {
printf("eFuse Two Point: Supported\n");
} else {
printf("Cannot retrieve eFuse Two Point calibration values. Default calibration values will be used.\n");
}
#else
#error "This example is configured for ESP32/ESP32S2."
#endif
}
static void print_char_val_type(esp_adc_cal_value_t val_type)
{
if (val_type == ESP_ADC_CAL_VAL_EFUSE_TP) {
@ -58,14 +66,12 @@ static void print_char_val_type(esp_adc_cal_value_t val_type)
printf("Characterized using Default Vref\n");
}
}
#endif
void app_main(void)
{
#if CONFIG_IDF_TARGET_ESP32
//Check if Two Point or Vref are burned into eFuse
check_efuse();
#endif
//Configure ADC
if (unit == ADC_UNIT_1) {
@ -75,12 +81,10 @@ void app_main(void)
adc2_config_channel_atten((adc2_channel_t)channel, atten);
}
#if CONFIG_IDF_TARGET_ESP32
//Characterize ADC
adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));
esp_adc_cal_value_t val_type = esp_adc_cal_characterize(unit, atten, width, DEFAULT_VREF, adc_chars);
print_char_val_type(val_type);
#endif
//Continuously sample ADC1
while (1) {
@ -96,13 +100,9 @@ void app_main(void)
}
}
adc_reading /= NO_OF_SAMPLES;
#if CONFIG_IDF_TARGET_ESP32
//Convert adc_reading to voltage in mV
uint32_t voltage = esp_adc_cal_raw_to_voltage(adc_reading, adc_chars);
printf("Raw: %d\tVoltage: %dmV\n", adc_reading, voltage);
#elif CONFIG_IDF_TARGET_ESP32S2
printf("ADC%d CH%d Raw: %d\t\n", unit, channel, adc_reading);
#endif
vTaskDelay(pdMS_TO_TICKS(1000));
}
}

2
examples/peripherals/adc2/main/adc2_example_main.c
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@ -45,7 +45,7 @@ void app_main(void)
//be sure to do the init before using adc2.
printf("adc2_init...\n");
adc2_config_channel_atten( ADC2_EXAMPLE_CHANNEL, ADC_ATTEN_0db );
adc2_config_channel_atten( ADC2_EXAMPLE_CHANNEL, ADC_ATTEN_11db );
vTaskDelay(2 * portTICK_PERIOD_MS);