ESP32-C3 ADC와 터치 센서 — 아날로그 입력 처리

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#include "esp_adc/adc_oneshot.h"
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#include "esp_adc/adc_cali.h"
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#include "esp_adc/adc_cali_scheme.h"
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adc_oneshot_unit_handle_t adc1;
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adc_cali_handle_t cali;
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void setup_adc(void) {
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    adc_oneshot_unit_init_cfg_t init_cfg = {
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        .unit_id = ADC_UNIT_1,
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        .ulp_mode = ADC_ULP_MODE_DISABLE,
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    };
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    adc_oneshot_new_unit(&init_cfg, &adc1);
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    adc_oneshot_chan_cfg_t chan_cfg = {
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        .bitwidth = ADC_BITWIDTH_12,
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        .atten = ADC_ATTEN_DB_12,
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    };
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    adc_oneshot_config_channel(adc1, ADC_CHANNEL_0, &chan_cfg);   // GPIO0
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    // 캘리브레이션 (Curve Fitting scheme, C3에서 기본)
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    adc_cali_curve_fitting_config_t cali_cfg = {
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        .unit_id = ADC_UNIT_1,
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        .atten = ADC_ATTEN_DB_12,
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        .bitwidth = ADC_BITWIDTH_12,
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    };
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    adc_cali_create_scheme_curve_fitting(&cali_cfg, &cali);
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}
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int read_voltage_mv(void) {
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    int raw;
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    adc_oneshot_read(adc1, ADC_CHANNEL_0, &raw);
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    int voltage_mv;
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    adc_cali_raw_to_voltage(cali, raw, &voltage_mv);
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    return voltage_mv;
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}

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esp_err_t err = adc_cali_create_scheme_curve_fitting(&cfg, &cali);
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if (err == ESP_ERR_NOT_SUPPORTED) {
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    printf("Calibration not burned, falling back\n");
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    // Vref 1100 mV 가정한 manual conversion
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    voltage_mv = raw * 1100 / 4095;
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}

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#define BATTERY_DIVIDER_RATIO 2.0f
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float read_battery_voltage(void) {
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    int sum = 0;
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    const int N = 32;
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    for (int i = 0; i < N; i++) {
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        int raw;
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        adc_oneshot_read(adc1, ADC_CHANNEL_0, &raw);
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        sum += raw;
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    }
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    int avg_raw = sum / N;
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    int voltage_mv;
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    adc_cali_raw_to_voltage(cali, avg_raw, &voltage_mv);
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    return (voltage_mv * BATTERY_DIVIDER_RATIO) / 1000.0f;
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}

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#include "esp_adc/adc_continuous.h"
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adc_continuous_handle_t handle;
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void setup_continuous(void) {
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    adc_continuous_handle_cfg_t handle_cfg = {
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        .max_store_buf_size = 4096,
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        .conv_frame_size = 256,
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    };
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    adc_continuous_new_handle(&handle_cfg, &handle);
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    adc_digi_pattern_config_t pat[1] = {
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        {
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            .atten = ADC_ATTEN_DB_12,
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            .channel = ADC_CHANNEL_0,
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            .unit = ADC_UNIT_1,
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            .bit_width = ADC_BITWIDTH_12,
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        }
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    };
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    adc_continuous_config_t cont_cfg = {
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        .pattern_num = 1,
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        .adc_pattern = pat,
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        .sample_freq_hz = 20000,         // 20 kHz
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        .conv_mode = ADC_CONV_SINGLE_UNIT_1,
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        .format = ADC_DIGI_OUTPUT_FORMAT_TYPE2,
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    };
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    adc_continuous_config(handle, &cont_cfg);
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    adc_continuous_start(handle);
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}
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void read_continuous(void) {
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    uint8_t buf[256];
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    uint32_t bytes_read;
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    while (1) {
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        if (adc_continuous_read(handle, buf, sizeof(buf),
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                                 &bytes_read, 100) == ESP_OK) {
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            // buf 안에 adc_digi_output_data_t 구조체 배열
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            for (int i = 0; i < bytes_read; i += sizeof(adc_digi_output_data_t)) {
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                adc_digi_output_data_t *p = (void*)(buf + i);
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                // p->type2.data, p->type2.channel
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            }
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        }
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    }
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}

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// 1. Multisampling (가장 흔함)
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int read_avg(int channel, int n) {
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    int sum = 0;
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    for (int i = 0; i < n; i++) {
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        int raw;
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        adc_oneshot_read(adc1, channel, &raw);
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        sum += raw;
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    }
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    return sum / n;
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}
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// 2. Median filter (스파이크 제거)
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int read_median(int channel, int n) {
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    int samples[n];
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    for (int i = 0; i < n; i++) {
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        adc_oneshot_read(adc1, channel, &samples[i]);
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    }
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    // qsort + 중앙값 반환
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    qsort(samples, n, sizeof(int), int_compare);
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    return samples[n / 2];
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}
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// 3. Exponential moving average (저주파 추적)
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float ema = 0;
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const float alpha = 0.1f;
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void update(int channel) {
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    int raw;
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    adc_oneshot_read(adc1, channel, &raw);
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    ema = alpha * raw + (1.0f - alpha) * ema;
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}

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// 9장에서 다룰 deep-sleep + GPIO wake
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esp_sleep_enable_gpio_wakeup();
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gpio_wakeup_enable(GPIO_NUM_9, GPIO_INTR_LOW_LEVEL);
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esp_deep_sleep_start();