linux UART

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

 int set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop)
 {
     struct termios newtio,oldtio;
     if  ( tcgetattr( fd,&oldtio)  !=  )
     {
         perror("SetupSerial 1");
         return -;
     }
     bzero( &newtio, sizeof( newtio ) );
     newtio.c_cflag  |=  CLOCAL | CREAD;
     newtio.c_cflag &= ~CSIZE;

     switch( nBits )
     {
     case :
         newtio.c_cflag |= CS7;
         break;
     case :
         newtio.c_cflag |= CS8;
         break;
     }

     switch( nEvent )
     {
     case 'O':                     //奇校验
         newtio.c_cflag |= PARENB;
         newtio.c_cflag |= PARODD;
         newtio.c_iflag |= (INPCK | ISTRIP);
         break;
     case 'E':                     //偶校验
         newtio.c_iflag |= (INPCK | ISTRIP);
         newtio.c_cflag |= PARENB;
         newtio.c_cflag &= ~PARODD;
         break;
     case 'N':                    //无校验
         newtio.c_cflag &= ~PARENB;
         break;
     }

     switch( nSpeed )
     {
     case :
         cfsetispeed(&newtio, B2400);
         cfsetospeed(&newtio, B2400);
         break;
     case :
         cfsetispeed(&newtio, B4800);
         cfsetospeed(&newtio, B4800);
         break;
     case :
         cfsetispeed(&newtio, B9600);
         cfsetospeed(&newtio, B9600);
         break;
     case :
         cfsetispeed(&newtio, B115200);
         cfsetospeed(&newtio, B115200);
         break;
     default:
         cfsetispeed(&newtio, B9600);
         cfsetospeed(&newtio, B9600);
         break;
     }
     if( nStop ==  )
     {
         newtio.c_cflag &=  ~CSTOPB;
     }
     else if ( nStop ==  )
     {
         newtio.c_cflag |=  CSTOPB;
     }
     newtio.c_cc[VTIME]  = ;
     newtio.c_cc[VMIN] = ;
     tcflush(fd,TCIFLUSH);
     if((tcsetattr(fd,TCSANOW,&newtio))!=)
     {
         perror("com set error");
         return -;
     }
     printf("set done!\n");
     return ;
 }

 int open_port(int fd,int comport)
 {
     char *dev[]={"/dev/ttySAC0","/dev/ttySAC1","/dev/ttySAC3","/dev/ttySAC4"};
     long  vdisable;
     if (comport==)
     {
         fd = open( dev[comport - ], O_RDWR|O_NOCTTY|O_NDELAY);
         if (- == fd)
         {
             perror("Can't Open Serial Port");
             return(-);
         }
         else
         {
             printf("%s .....\n", dev[comport - ]);
         }
     }
     else if(comport==)
     {    fd = open( dev[comport - ], O_RDWR|O_NOCTTY|O_NDELAY);
         if (- == fd)
         {
             perror("Can't Open Serial Port");
             return(-);
         }
         else
         {
             printf("%s .....\n", dev[comport - ]);
         }
     }
     else if (comport==)
     {
         fd = open( dev[comport - ], O_RDWR|O_NOCTTY|O_NDELAY);
         if (- == fd)
         {
             perror("Can't Open Serial Port");
             return(-);
         }
         else
         {
             printf("%s .....\n", dev[comport - ]);
         }
     }
     if(fcntl(fd, F_SETFL, )<)
     {
         printf("fcntl failed!\n");
     }
     else
     {
         printf("fcntl=%d\n",fcntl(fd, F_SETFL,));
     }
     if(isatty(STDIN_FILENO)==)
     {
         printf("standard input is not a terminal device\n");
     }
     else
     {
         printf("isatty success!\n");
     }
     printf("fd-open=%d\n",fd);
     return fd;
 }

 int main(void)
 {
     int fd;
     int nread,i;
     char buff[]="Hello\n";

     if((fd=open_port(fd,))<)
     {
         perror("open_port error");
         return;
     }
     if((i=set_opt(fd,,,'N',))<)
     {
         perror("set_opt error");
         return;
     }
     printf("fd=%d\n",fd);
     while(){
         errno = ;
         nread=read(fd,buff,);
         if( < nread){
             printf("nread=%d,%s\n",nread,buff);
         }
     }
     close(fd);
     return;
 }