两个麦克风实时声源方向检测mbed代码

以下是基于mbed平台的两个麦克风实时声源方向检测的示例代码：

#include "mbed.h"
#include "USBSerial.h"
#include "SDFileSystem.h"
#include "FastAnalogIn.h"

#define SAMPLE_RATE 16000
#define FRAME_SIZE 256
#define BUFFER_SIZE (FRAME_SIZE * 2)

#define MIC1_PIN A0
#define MIC2_PIN A1

#define MIC1_WEIGHT 1
#define MIC2_WEIGHT 1

#define MIC1_DELAY_US 0
#define MIC2_DELAY_US 1000

FastAnalogIn mic1(MIC1_PIN);
FastAnalogIn mic2(MIC2_PIN);

Timer timer;

int16_t buffer[BUFFER_SIZE];
int16_t frame[FRAME_SIZE];
int16_t xcorr[FRAME_SIZE];

void normalize(int16_t *samples, int size) {
    int16_t max = 0;
    for (int i = 0; i < size; i++) {
        if (abs(samples[i]) > max) {
            max = abs(samples[i]);
        }
    }

    if (max > 0) {
        float scale = 32767.0f / max;
        for (int i = 0; i < size; i++) {
            samples[i] = (int16_t)(samples[i] * scale);
        }
    }
}

float cross_correlation(int16_t *x, int16_t *y, int size) {
    float sum = 0;
    for (int i = 0; i < size; i++) {
        sum += x[i] * y[i];
    }
    return sum;
}

void process_frame() {
    // read data from mic1 and mic2
    for (int i = 0; i < FRAME_SIZE; i++) {
        buffer[i] = mic1.read_u16() - 32768;
        buffer[i + FRAME_SIZE] = mic2.read_u16() - 32768;
    }

    // apply weights and delays
    for (int i = 0; i < FRAME_SIZE; i++) {
        int16_t mic1_sample = buffer[i] * MIC1_WEIGHT;
        int16_t mic2_sample = buffer[i + FRAME_SIZE] * MIC2_WEIGHT;

        int16_t mic1_delayed = buffer[i] * MIC1_WEIGHT;
        int16_t mic2_delayed = buffer[i + FRAME_SIZE] * MIC2_WEIGHT;

        if (MIC1_DELAY_US > 0) {
            mic1_delayed = buffer[i - MIC1_DELAY_US * SAMPLE_RATE / 1000000] * MIC1_WEIGHT;
        }

        if (MIC2_DELAY_US > 0) {
            mic2_delayed = buffer[i + FRAME_SIZE - MIC2_DELAY_US * SAMPLE_RATE / 1000000] * MIC2_WEIGHT;
        }

        frame[i] = mic1_sample + mic2_delayed;
        frame[i] = mic2_sample + mic1_delayed;
    }

    // normalize samples
    normalize(frame, FRAME_SIZE);

    // calculate cross-correlation
    for (int i = 0; i < FRAME_SIZE; i++) {
        int16_t *x = &frame[0];
        int16_t *y = &frame[i];
        xcorr[i] = cross_correlation(x, y, FRAME_SIZE - i);
    }

    // find peak of cross-correlation
    int peak_index = 0;
    float peak_value = xcorr[0];
    for (int i = 1; i < FRAME_SIZE; i++) {
        if (xcorr[i] > peak_value) {
            peak_index = i;
            peak_value = xcorr[i];
        }
    }

    // calculate direction of arrival
    float direction = (float)(peak_index * SAMPLE_RATE / FRAME_SIZE);
    printf("Direction: %.1f\r\n", direction);
}

int main() {
    timer.start();

    while (1) {
        process_frame();

        while (timer.read_us() < FRAME_SIZE * 1000000 / SAMPLE_RATE) {
            // wait for next frame
        }
        timer.reset();
    }
}

上述代码实现了基于交叉相关函数的声源方向检测。其中，`MIC1_PIN`和`MIC2_PIN`分别表示麦克风1和麦克风2的引脚，`MIC1_WEIGHT`和`MIC2_WEIGHT`分别表示相应麦克风采样值的权重，`MIC1_DELAY_US`和`MIC2_DELAY_US`分别表示相应麦克风的延迟时间（单位为微秒）。通过调整这些参数，可以适应不同的环境和应用场景。

需要注意的是，在实际应用中，可能需要对采样值进行滤波、增益等处理，以提高检测的准确性和鲁棒性。