com.c

在Linux上实现对串口设备的读写程序

int open_port(int fd,int comport)
{
   char *dev[]={"/dev/ttyS0","/dev/ttyS1","/dev/ttyS2"};
   long vdisable;
   if(comport == 1)
     {
        fd = open("/dev/ttyS0",O_RDWR|O_NOCITY|O_NEDLAY);
        if(-1 == fd)
        {
           perror("can't open serial port");
           return -1;
        }
     }
     else if(comport == 2)
     {
        fd = open("/dev/ttyS1",O_RDWR|O_NOCITY|O_NEDLAY);
        if(-1 == fd)
        {
           perror("can't open serial port");
           return -1;
        }
     }
     else if(comport == 3)
     {
        fd = open("/dev/ttyS2",O_RDWR|O_NOCITY|O_NEDLAY);
        if(-1 == fd)
        {
           perror("can't open serial port");
           return -1;
        }     
     }
     if(fcntl(fd,F_SETFL,0)<0)
         printf("fcntl failed!\n");
     else
         printf(fcntl = %d\n",fcntl(fd,F_SETFL,0));
         
     if(isatty(STDIN_FILENO) == 0)
     		printf("standard input is not a terminal device \n");
     else
     		printf("isatty success!\n");
     printf("fd-open=%d\n",fd);
     return fd;
}

int set_opt(int fd,int nSpeed,int nBits,char nEvent,int nStop)
{
  struct termios newtio,oldtio;
  if(tcgetattr(fd,&oldtio)!=0)
  {
    perror("SetupSerial 1");
    return -1;
  }
  
  bzero(&newtio,sizeof(newtio));
  
  newtio.c_cflag |= CLOAL | CREAD;
  newtio.c_cflag &= ~CSIZE;
  
  switch(nBits)
  {
    case 7:
           newtio.c_cflag |= CS7;
           break;
    case 8:
    			 newtio.c_cflag |= CS8;
    			 break;
  }
  
  switch(nEvent)
  {
   case 'O':
           newtio.c_cflag |= PARENB;
           newtio.c_cflag |= PARODD;
           newtio.c_cflag |= (INPCK | ISTRIP);
           break;
   case 'E':
           newtio.c_cflag |= PARENB;
           newtio.c_cflag &= ~PARODD;
           newtio.c_cflag |= (INPCK | ISTRIP);
           break;
   case 'N':
           newtio.c_cflag &=~ PARENB;
           break;
  }
  
  switch(nSpeed)
  {
    case 2400:
            cfsetispeed(&newtio,B2400);
            cfsetospeed(&newtio,B2400);
            break;
    case 4800:
            cfsetispeed(&newtio,B4800);
            cfsetospeed(&newtio,B4800);
            break;
    case 9600:
            cfsetispeed(&newtio,B9600);
            cfsetospeed(&newtio,B9600);
            break;
    case 115200:
            cfsetispeed(&newtio,B115200);
            cfsetospeed(&newtio,B115200);
            break;
    case 460800:
            cfsetispeed(&newtio,B460800);
            cfsetospeed(&newtio,B460800);
            break;
    default:
            cfsetispeed(&newtio,B115200);
            cfsetospeed(&newtio,B115200);
            break;            
  }
  if(nStop == 1)
  				  newtio.c_cflag &= ~CSTOPB;
  else if(nStop == 2)
  				  newtio.c_cflag |= CSTOPB;
  newtio.c_cc[VIIME] = 0;
  newtio.c_cc[VMIN] = 0;
  tcflush(fd,TCIFLUSH);
  
  if((tcsetattr(fd,TCSANOW,&newtio))!=0)
  {
    perror("com set error");
    return -1;
  }
  printf("set done!\n");
  return 0;
}


#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 main(void)
{
  int fd;
  int nread,i;
  char buff[]="Hello\n";
  
  if((fd = open_port(fd,1))<0)
  {
    perror("open_port error");
    return;
  }
  if((i=set_opt(fd,115200,8,'N',1))<0)
  {
    perror("set_opt error");
    return;
  }
  printf("fd=%d\n",fd);
  fd = 3;
  nread = read(fd,buff,8);
  printf("nread=%d,%s\n",nread,buff);
  close(fd);
  return;
}