linux uart 编程

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>

int set_interface_attribs(int fd, int speed, int parity) {
    struct termios tty;
    memset(&tty, 0, sizeof(tty));
    if (tcgetattr(fd, &tty) != 0) {
        perror("error from tcgetattr");
        return -1;
    }

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

    tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
    tty.c_iflag &= ~IGNBRK;         // disable break processing
    tty.c_lflag = 0;                // no signaling chars, no echo, no canonical processing
    tty.c_oflag = 0;                // no remapping, no delays
    tty.c_cc[VMIN]  = 0;            // read doesn't block
    tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout

    tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off s/w flow ctrl
    tty.c_cflag |= (CLOCAL | CREAD);        // ignore modem controls, enable reading
    tty.c_cflag &= ~(PARENB | PARODD);      // shut off parity
    tty.c_cflag |= parity;
    tty.c_cflag &= ~CSTOPB;
    tty.c_cflag &= ~CRTSCTS;

    if (tcsetattr(fd, TCSANOW, &tty) != 0) {
        perror("error from tcsetattr");
        return -1;
    }
    return 0;
}

void set_blocking(int fd, int should_block) {
    struct termios tty;
    memset(&tty, 0, sizeof(tty));
    if (tcgetattr(fd, &tty) != 0) {
        perror("error from tggetattr");
        return;
    }

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

    if (tcsetattr(fd, TCSANOW, &tty) != 0)
        perror("error setting term attributes");
}

int main() {
    char *portname = "/dev/ttyUSB0";
    int fd = open(portname, O_RDWR | O_NOCTTY | O_SYNC);
    if (fd < 0) {
        perror("error opening %s: %s", portname, strerror(errno));
        return -1;
    }

    set_interface_attribs(fd, B9600, 0);  // set speed to 9600 baud, 8N1 (no parity)
    set_blocking(fd, 0);                // set non-blocking

    char buf[100];
    while (1) {
        int n = read(fd, buf, sizeof(buf));
        if (n > 0) {
            write(STDOUT_FILENO, buf, n);
        }
    }

    close(fd);
    return 0;
}