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

#define SERIAL_PORT "/dev/ttyS0" // 根据你的设备修改串口设备文件路径

int main() {
    int serial_fd;
    struct termios options;
    char *port = SERIAL_PORT;
    char readbuffer[256];
    fd_set readfds;
    struct timeval timeout;

    // 打开串口
    serial_fd = open(port, O_RDWR | O_NOCTTY | O_NDELAY);
    if (serial_fd == -1) {
        perror("open_port: Unable to open device");
        return -1;
    }

    // 获取当前串口设置
    tcgetattr(serial_fd, &options);

    // 设置波特率
    cfsetispeed(&options, B9600);
    cfsetospeed(&options, B9600);

    // 设置串口参数：8位数据位，1位停止位，无奇偶校验位
    options.c_cflag &= ~PARENB; // Clear parity bit, no parity
    options.c_cflag &= ~CSTOPB; // Clear stop field, only one stop bit used in communication
    options.c_cflag &= ~CSIZE; // Clear all the size bits
    options.c_cflag |= CS8; // 8 data bits
    options.c_cflag &= ~CRTSCTS; // Disable RTS/CTS hardware flow control
    options.c_lflag &= ~ICANON;
    options.c_lflag &= ~ECHO; // Disable echo
    options.c_lflag &= ~ECHOE; // Disable erasure
    options.c_lflag &= ~ECHONL; // Disable new-line echo
    options.c_lflag &= ~ISIG; // Disable interpretation of INTR, QUIT and SUSP
    options.c_iflag &= ~(IXON | IXOFF | IXANY); // Turn off s/w flow ctrl
    options.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR); // Disable special handling of received bytes

    // 设置输入输出的VMIN和VTIME
    options.c_cc[VMIN] = 0;
    options.c_cc[VTIME] = 5;

    // 应用串口参数
    tcsetattr(serial_fd, TCSANOW, &options);

    printf("Configuring the serial port completed\n");

    // 发送数据
    char *msg = "Hello, Serial Port!\n";
    write(serial_fd, msg, strlen(msg));

    // 使用select等待数据
    while (1) {
        FD_ZERO(&readfds);
        FD_SET(serial_fd, &readfds);

        // 设置超时时间
        timeout.tv_sec = 5;  // 5 seconds
        timeout.tv_usec = 0;

        // 等待串口数据，超时返回
        int ret = select(serial_fd + 1, &readfds, NULL, NULL, &timeout);
        if (ret == -1) {
            perror("select error");
            break;
        } else if (ret == 0) {
            printf("select timeout\n");
            continue;
        } else {
            if (FD_ISSET(serial_fd, &readfds)) {
                memset(readbuffer, 0, sizeof(readbuffer));
                int n = read(serial_fd, readbuffer, sizeof(readbuffer));
                if (n > 0) {
                    printf("Data Received: %s", readbuffer);
                }
            }
        }
    }

    // 关闭串口
    close(serial_fd);

    return 0;
}