[技術] 在Linux上用C撰寫RS-232通訊程式

Written on 12:41 下午 by Yu Lai

最近工作上玩到的，總結一下當Note吧。
主要是Ref: Serial Programming Guide for POSIX Operating Systems。
配合pthread把收跟送的部份分開，
以下是收的部份。

struct tty_q {
 int len;
 unsigned char buff[TTY_Q_SZ]; /* TTY_Q_SZ=1024 */
} tty_q;

int tty_fd;
pthread_mutex_t tty_mutex;

void * rs232com(void *arg) {

 int c=0, len;
 struct termios oldtio, newtio;
 char buf[256];

 pthread_detach(pthread_self());
 pthread_mutex_init(&tty_mutex, NULL);

 /* Open the rs232 port */
 tty_fd = open(TTYDEVICE, O_RDWR|O_NOCTTY);
 if (tty_fd < 0) {
  perror(TTYDEVICE);
  exit(1);
 }

 /* Get the current options */
 tcgetattr(tty_fd, &oldtio);

 /* Set new options */
 bzero(&newtio, sizeof(newtio));
 newtio.c_cflag = BAUDRATE|CS8|CLOCAL|CREAD;
 newtio.c_iflag = IGNPAR;
 newtio.c_oflag = 0;
 newtio.c_lflag = ICANON;
 
 /* Set the options */
 tcflush(tty_fd, TCIFLUSH);
 tcsetattr(tty_fd, TCSANOW, &newtio);

 while(1) {
  len = read(tty_fd, buf, 255);
  buf[len]=0;

  MCP_LOG("RS-232 recv, len=%03d, buf=%s\n", len, buf);

  pthread_mutex_lock(&tty_mutex);

  if(tty_q.len + len > TTY_Q_SZ) {
   memset(tty_q.buff, 0, TTY_Q_SZ);
   tty_q.len = 0;
  }

  memcpy(&tty_q.buff[tty_q.len], buf, len);
  tty_q.len += len;

  pthread_mutex_unlock(&tty_mutex);
 }
}

而送的部份在這裡。
int rs232send(U8 * buf) {

 pthread_mutex_lock(&tty_mutex);

 memset(tty_q.buff, 0, TTY_Q_SZ);
 tty_q.len = 0;

 pthread_mutex_unlock(&tty_mutex);

 return write(tty_fd, buf, strlen(buf));

}

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