adc: rename adc examples according to hw feature and usage

examples/peripherals/adc/single_read/adc/CMakeLists.txt

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+# The following lines of boilerplate have to be in your project's CMakeLists
+# in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.5)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(adc)

examples/peripherals/adc/single_read/adc/Makefile

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+#
+# This is a project Makefile. It is assumed the directory this Makefile resides in is a
+# project subdirectory.
+#
+
+PROJECT_NAME := adc
+
+include $(IDF_PATH)/make/project.mk

examples/peripherals/adc/single_read/adc/README.md

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+| Supported Targets | ESP32 |
+| ----------------- | ----- |
+
+# ADC1 Example
+
+(See the README.md file in the upper level 'examples' directory for more information about examples.)
+
+This example shows how to configure ADC1 and read the voltage connected to GPIO pin.
+
+## How to use example
+
+### Hardware Required
+
+* A development board with ESP32 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
+* A USB cable for power supply and programming
+
+In this example, we use `ADC_UNIT_1` by default, we need to connect a voltage source (0 ~ 3.3v) to GPIO34. If another ADC unit is selected in your application, you need to change the GPIO pin (please refer to Chapter 4.11 of the `ESP32 Technical Reference Manual`).
+
+### Configure the project
+
+```
+idf.py menuconfig
+```
+
+### Build and Flash
+
+Build the project and flash it to the board, then run monitor tool to view serial output:
+
+```
+idf.py -p PORT flash monitor
+```
+
+(To exit the serial monitor, type ``Ctrl-]``.)
+
+See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
+
+## Example Output
+
+Running this example, you will see the following log output on the serial monitor:
+
+```
+Raw: 486	Voltage: 189mV
+Raw: 435	Voltage: 177mV
+Raw: 225	Voltage: 128mV
+Raw: 18	    Voltage: 79mV
+```
+
+## Troubleshooting
+
+* program upload failure
+
+    * Hardware connection is not correct: run `idf.py -p PORT monitor`, and reboot your board to see if there are any output logs.
+    * The baud rate for downloading is too high: lower your baud rate in the `menuconfig` menu, and try again.
+
+For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.

examples/peripherals/adc/single_read/adc/main/CMakeLists.txt

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+idf_component_register(SRCS "adc1_example_main.c"
+                    INCLUDE_DIRS ".")

examples/peripherals/adc/single_read/adc/main/adc1_example_main.c

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+/* ADC1 Example
+
+   This example code is in the Public Domain (or CC0 licensed, at your option.)
+
+   Unless required by applicable law or agreed to in writing, this
+   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+   CONDITIONS OF ANY KIND, either express or implied.
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "driver/gpio.h"
+#include "driver/adc.h"
+#include "esp_adc_cal.h"
+
+#define DEFAULT_VREF    1100        //Use adc2_vref_to_gpio() to obtain a better estimate
+#define NO_OF_SAMPLES   64          //Multisampling
+
+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
+static const adc_channel_t channel = ADC_CHANNEL_6;     // GPIO7 if ADC1, GPIO17 if ADC2
+static const adc_bits_width_t width = ADC_WIDTH_BIT_13;
+#endif
+static const adc_atten_t atten = ADC_ATTEN_DB_0;
+static const adc_unit_t unit = ADC_UNIT_1;
+
+
+static void check_efuse(void)
+{
+#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) {
+        printf("Characterized using Two Point Value\n");
+    } else if (val_type == ESP_ADC_CAL_VAL_EFUSE_VREF) {
+        printf("Characterized using eFuse Vref\n");
+    } else {
+        printf("Characterized using Default Vref\n");
+    }
+}
+
+
+void app_main(void)
+{
+    //Check if Two Point or Vref are burned into eFuse
+    check_efuse();
+
+    //Configure ADC
+    if (unit == ADC_UNIT_1) {
+        adc1_config_width(width);
+        adc1_config_channel_atten(channel, atten);
+    } else {
+        adc2_config_channel_atten((adc2_channel_t)channel, atten);
+    }
+
+    //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);
+
+    //Continuously sample ADC1
+    while (1) {
+        uint32_t adc_reading = 0;
+        //Multisampling
+        for (int i = 0; i < NO_OF_SAMPLES; i++) {
+            if (unit == ADC_UNIT_1) {
+                adc_reading += adc1_get_raw((adc1_channel_t)channel);
+            } else {
+                int raw;
+                adc2_get_raw((adc2_channel_t)channel, width, &raw);
+                adc_reading += raw;
+            }
+        }
+        adc_reading /= NO_OF_SAMPLES;
+        //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);
+        vTaskDelay(pdMS_TO_TICKS(1000));
+    }
+}

examples/peripherals/adc/single_read/adc/main/component.mk

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+#
+# Main Makefile. This is basically the same as a component makefile.
+#