嵌入式 ANC：ESP32 实战

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#include "driver/i2s.h"

#define I2S_SAMPLE_RATE     16000
#define I2S_BUFFER_SIZE     1024

void i2s_mic_init(void) {
    i2s_config_t i2s_config = {
        .mode = I2S_MODE_MASTER | I2S_MODE_RX,
        .sample_rate = I2S_SAMPLE_RATE,
        .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
        .channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
        .communication_format = I2S_COMM_FORMAT_STAND_I2S,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
        .dma_buf_count = 4,
        .dma_buf_len = I2S_BUFFER_SIZE,
        .use_apll = true,
        .tx_desc_auto_clear = false,
        .fixed_mclk = 0
    };

    i2s_pin_config_t pin_config = {
        .bck_io_num = GPIO_NUM_4,
        .ws_io_num = GPIO_NUM_5,
        .data_out_num = I2S_PIN_NO_CHANGE,
        .data_in_num = GPIO_NUM_6
    };

    i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
    i2s_set_pin(I2S_NUM_0, &pin_config);
}

void read_mic_samples(int16_t *buffer, size_t len) {
    size_t bytes_read;
    i2s_read(I2S_NUM_0, buffer, len * sizeof(int16_t), &bytes_read, portMAX_DELAY);
}

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#include "esp_dsp.h"
#include "driver/i2s.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"

#define SAMPLE_RATE     16000
#define FRAME_SIZE      128
#define FILTER_ORDER    64

typedef struct {
    float w[FILTER_ORDER];          // 滤波器系数
    float x_ring[FILTER_ORDER];     // 参考信号环形缓冲区
    float s_hat[32];                // 次级路径估计
    float s_ring[32];               // 滤波后信号环形缓冲区
    int w_ptr;                      // 环形缓冲区写指针
    int s_ptr;
    float mu;                       // 自适应步长
} ESP32_ANC;

static ESP32_ANC g_anc;

void esp_anc_init(void) {
    memset(&g_anc, 0, sizeof(g_anc));
    g_anc.mu = 0.0005f;
    dsps_fft2r_init_fc32(NULL, CONFIG_DSP_MAX_FFT_SIZE);
}

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static inline float fast_convolve(const float *w, const float *x, int ptr, int len) {
    float output = 0.0f;
    for (int i = 0; i < len; i++) {
        int idx = (ptr + len - i) % len;
        output += w[i] * x[idx];
    }
    return output;
}

void esp_anc_process_frame(float *ref, float *err, float *out, int len) {
    for (int n = 0; n < len; n++) {
        g_anc.x_ring[g_anc.w_ptr] = ref[n];
        g_anc.s_ring[g_anc.s_ptr] = ref[n];

        float y = fast_convolve(g_anc.w, g_anc.x_ring, g_anc.w_ptr, FILTER_ORDER);
        float x_filt = fast_convolve(g_anc.s_hat, g_anc.s_ring, g_anc.s_ptr, 32);

        float power = 0.0f;
        for (int i = 0; i < FILTER_ORDER; i++)
            power += g_anc.x_ring[i] * g_anc.x_ring[i];
        float norm_step = g_anc.mu / (power + 1e-6f);

        for (int i = 0; i < FILTER_ORDER; i++) {
            int idx = (g_anc.w_ptr + FILTER_ORDER - i) % FILTER_ORDER;
            g_anc.w[i] += norm_step * err[n] * g_anc.x_ring[idx];
        }

        out[n] = y;
        g_anc.w_ptr = (g_anc.w_ptr + 1) % FILTER_ORDER;
        g_anc.s_ptr = (g_anc.s_ptr + 1) % 32;
    }
}