epoll 读串口例子

以下是一个使用 epoll 读取串口数据的示例代码，供您参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <sys/epoll.h>

#define MAX_EVENTS 10
#define BUF_SIZE 256

int set_interface_attribs(int fd, int speed) {
    struct termios tty;
    memset(&tty, 0, sizeof(tty));
    if (tcgetattr(fd, &tty) != 0) {
        printf("Error %d from tcgetattr\n", errno);
        return -1;
    }

    cfsetospeed(&tty, (speed_t)speed);
    cfsetispeed(&tty, (speed_t)speed);

    tty.c_cflag |= (CLOCAL | CREAD);    // ignore modem controls
    tty.c_cflag &= ~CSIZE;
    tty.c_cflag |= CS8;         // 8-bit characters
    tty.c_cflag &= ~PARENB;     // no parity bit
    tty.c_cflag &= ~CSTOPB;     // only need 1 stop bit
    tty.c_cflag &= ~CRTSCTS;    // no hardware flowcontrol

    // setup for non-canonical mode
    tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON);
    tty.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
    tty.c_oflag &= ~OPOST;

    // fetch bytes as they become available
    tty.c_cc[VMIN] = 1;
    tty.c_cc[VTIME] = 1;

    if (tcsetattr(fd, TCSANOW, &tty) != 0) {
        printf("Error %d from tcsetattr\n", errno);
        return -1;
    }
    return 0;
}

int set_blocking(int fd, int should_block) {
    struct termios tty;
    memset(&tty, 0, sizeof(tty));
    if (tcgetattr(fd, &tty) != 0) {
        printf("Error %d from tggetattr\n", errno);
        return -1;
    }

    tty.c_cc[VMIN] = should_block ? 1 : 0;
    tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout

    if (tcsetattr(fd, TCSANOW, &tty) != 0) {
        printf("Error %d setting term attributes\n", errno);
        return -1;
    }
    return 0;
}

int main() {
    int fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_SYNC);
    if (fd < 0) {
        printf("Error %d opening serial port\n", errno);
        return -1;
    }

    if (set_interface_attribs(fd, B9600) < 0) {
        printf("Error setting serial port attributes\n");
        return -1;
    }

    if (set_blocking(fd, 0) < 0) {
        printf("Error setting serial port blocking mode\n");
        return -1;
    }

    int efd = epoll_create1(0);
    if (efd == -1) {
        printf("Error %d creating epoll instance\n", errno);
        return -1;
    }

    struct epoll_event ev, events[MAX_EVENTS];
    ev.events = EPOLLIN;
    ev.data.fd = fd;
    if (epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ev) == -1) {
        printf("Error %d adding file descriptor to epoll instance\n", errno);
        return -1;
    }

    char buf[BUF_SIZE];
    while (1) {
        int n = epoll_wait(efd, events, MAX_EVENTS, -1);
        if (n == -1) {
            printf("Error %d from epoll_wait\n", errno);
            break;
        }

        for (int i = 0; i < n; i++) {
            if (events[i].events & EPOLLIN) {
                int len = read(fd, buf, BUF_SIZE);
                if (len > 0) {
                    buf[len] = 0;
                    printf("Received %d bytes: %s\n", len, buf);
                }
            }
        }
    }

    close(fd);
    close(efd);
    return 0;
}

此示例代码使用 epoll 监听串口的 EPOLLIN 事件，当有数据可读时，使用非阻塞读取方式从串口读取数据。在读取到数据后，将其打印到控制台上。同时，该示例代码也设置了串口的基本参数，以确保能够正确地读取串口数据。