thank you for your answer.now when I "cat /dev/tts/0,1,2..5". The system won't halt anymore.but I still can't receive GPS signal.

can you give me some advice?

thank you very much!

this is my setting for serial:

    struct termios newtio; 
 
    bzero(&newtio, sizeof(newtio)); 
 
    newtio.c_lflag &= ~(ECHO | ICANON| ECHOE | ISIG); 
    newtio.c_cflag = B115200 | CS8 | CLOCAL | CREAD; 
    newtio.c_iflag = IGNPAR; 
    newtio.c_oflag = 0; 
    newtio.c_oflag &= ~(OPOST); 
 
    newtio.c_cc[VTIME]    = 5;   /* inter-character timer unused */ 
    newtio.c_cc[VMIN]     = 0;   /* blocking read until 9 chars received */ 
 
    tcflush(fd, TCIFLUSH); 
    tcsetattr(fd,TCSANOW,&newtio);