Linux实时信号处理在通信中的应用过程

sudo apt update
sudo apt install build-essential

sudo apt install libasound2-dev

sudo apt install libfftw3-dev

aplay -l

**** List of PLAYBACK Hardware Devices ****
card 1: USB [USB PnP Sound Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>

#define PCM_DEVICE "default"

int main() {
    long loops;
    int rc;
    int size;
    snd_pcm_t *pcm_handle;
    snd_pcm_hw_params_t *params;
    snd_pcm_uframes_t frames;
    char *buffer;

    // 打开音频设备
    rc = snd_pcm_open(&pcm_handle, PCM_DEVICE, SND_PCM_STREAM_CAPTURE, 0);
    if (rc < 0) {
        fprintf(stderr, "无法打开音频设备 '%s': %s\n", PCM_DEVICE, snd_strerror(rc));
        return EXIT_FAILURE;
    }

    // 分配硬件参数对象
    snd_pcm_hw_params_alloca(&params);

    // 填充默认硬件参数
    snd_pcm_hw_params_any(pcm_handle, params);
    snd_pcm_hw_params_set_access(pcm_handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    snd_pcm_hw_params_set_format(pcm_handle, params, SND_PCM_FORMAT_S16_LE);
    snd_pcm_hw_params_set_channels(pcm_handle, params, 1);
    snd_pcm_hw_params_set_rate(pcm_handle, params, 44100, 0);
    frames = 32;
    snd_pcm_hw_params_set_period_size(pcm_handle, params, frames, 0);

    // 写入硬件参数
    rc = snd_pcm_hw_params(pcm_handle, params);
    if (rc < 0) {
        fprintf(stderr, "无法设置硬件参数: %s\n", snd_strerror(rc));
        return EXIT_FAILURE;
    }

    // 获取周期大小
    snd_pcm_hw_params_get_period_size(params, &frames, 0);
    size = frames * 2; // 2 bytes/sample, 1 channels
    buffer = (char *) malloc(size);

    // 开始音频采集
    snd_pcm_prepare(pcm_handle);
    for (loops = 0; loops < 10000; loops++) {
        rc = snd_pcm_readi(pcm_handle, buffer, frames);
        if (rc == -EPIPE) {
            // EPIPE means overrun
            fprintf(stderr, "缓冲区溢出。\n");
            snd_pcm_prepare(pcm_handle);
        } else if (rc < 0) {
            fprintf(stderr, "音频采集错误: %s\n", snd_strerror(rc));
        }
    }

    snd_pcm_drain(pcm_handle);
    snd_pcm_close(pcm_handle);
    free(buffer);

    return 0;
}

gcc -o signal_capture signal_capture.c -lasound

./signal_capture

#include <stdio.h>
#include <stdlib.h>
#include <fftw3.h>

#define SAMPLE_RATE 44100
#define BUFFER_SIZE 1024

int main() {
    fftw_complex *in, *out;
    fftw_plan p;
    int i;

    // 分配输入和输出数组
    in = (fftw_complex *) fftw_malloc(sizeof(fftw_complex) * BUFFER_SIZE);
    out = (fftw_complex *) fftw_malloc(sizeof(fftw_complex) * BUFFER_SIZE);

    // 创建FFT计划
    p = fftw_plan_dft_1d(BUFFER_SIZE, in, out, FFTW_FORWARD, FFTW_ESTIMATE);

    // 填充输入数组（这里使用随机数据模拟信号）
    for (i = 0; i < BUFFER_SIZE; i++) {
        in[i][0] = (double) rand() / RAND_MAX; // 实部
        in[i][1] = (double) rand() / RAND_MAX; // 虚部
    }

    // 执行FFT
    fftw_execute(p);

    // 输出FFT结果
    for (i = 0; i < BUFFER_SIZE; i++) {
        printf("频率：%d, 幅度：%f\n", i * SAMPLE_RATE / BUFFER_SIZE, out[i][0]);
    }

    // 清理资源
    fftw_destroy_plan(p);
    fftw_free(in);
    fftw_free(out);

    return 0;
}

gcc -o signal_processing signal_processing.c -lfftw3

./signal_processing

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 8888
#define BUFFER_SIZE 1024

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buffer[BUFFER_SIZE];

    // 创建UDP套接字
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("创建套接字失败");
        return -1;
    }

    // 配置服务器地址
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    inet_pton(AF_INET, SERVER_IP, &server_addr.sin_addr);

    // 模拟信号数据
    for (int i = 0; i < BUFFER_SIZE; i++) {
        buffer[i] = rand() % 256;
    }

    // 发送信号数据
    if (sendto(sockfd, buffer, BUFFER_SIZE, 0, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("发送数据失败");
        close(sockfd);
        return -1;
    }

    printf("信号数据已发送\n");

    close(sockfd);
    return 0;
}

gcc -o signal_transmit signal_transmit.c

./signal_transmit

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define SERVER_PORT 8888
#define BUFFER_SIZE 1024

int main() {
    int sockfd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_len;
    char buffer[BUFFER_SIZE];

    // 创建UDP套接字
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("创建套接字失败");
        return -1;
    }

    // 配置服务器地址
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    // 绑定套接字
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("绑定套接字失败");
        close(sockfd);
        return -1;
    }

    printf("等待接收信号数据...\n");

    client_len = sizeof(client_addr);
    if (recvfrom(sockfd, buffer, BUFFER_SIZE, 0, (struct sockaddr *)&client_addr, &client_len) < 0) {
        perror("接收数据失败");
        close(sockfd);
        return -1;
    }

    printf("接收到信号数据\n");

    // 模拟解调过程
    for (int i = 0; i < BUFFER_SIZE; i++) {
        buffer[i] = buffer[i] / 2; // 简单的解调示例
    }

    printf("解调后的信号数据已保存\n");

    close(sockfd);
    return 0;
}

gcc -o signal_receive signal_receive.c

./signal_receive

frames = 64;