Linux下打开串口设置

给出打开串口函数

int open_tty(char tty[])
{
	int fd;
	char tty_path[32]={0};
	sprintf(tty_path,"/dev/%s",tty);
	fd=tty_open_port(tty_path);
	// PORT_SPEED是一个定义的宏，表示传输速率。数据位为8，无校验位，停止位为1
	tty_set_opt(fd,PORT_SPEED,8,'N',1);
	return fd;
}

该函数接受一个参数，表示你要打开的串口名称，如“ttyS1”，返回串口操作描述符，在调用该函数后，可以根据返回值来判断是否设置成功，如果fd大于0，则返回成功。

该函数还依赖于两个函数，下面也给出（包括用到的头文件）。

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <error.h>
#include <sys/stat.h>
#include <unistd.h>
#include <termios.h>
#include <fcntl.h>
#include <stdlib.h>
extern int tty_open_port(char *tty_num);
extern int tty_set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop);
int tty_open_port(char *tty_num)
{
     int fd = open (tty_num, O_RDWR | O_NOCTTY | O_NDELAY );
     //阻塞 fcntl(fd,F_SETFL,0)  ; //block
     //非阻塞 fcntl(fd,F_SETFL,FNDELAY)  ;
      if (fd == -1)
      {
	  printf ("Can't Open Serial Port %s !\n",tty_num);
	  return -1;
      }
      else
      {
	   //将串口设置成非阻塞的操作
           fcntl(fd,F_SETFL,FNDELAY);
           return fd;
      }

}
/**************************************************************************************
* 功    能:set serial port speed
* 修改历史: 2011.6.29.
**************************************************************************************/
int tty_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  |=  CLOCAL | CREAD;
	newtio.c_cflag &= ~CSIZE;             //mask the character size bits

	switch( nBits )
	{
	case 7:
		newtio.c_cflag |= CS7;              //data: 7bits
		break;
	case 8:
		newtio.c_cflag |= CS8;              //data: 8bits
		break;
	}

	switch( nEvent )
	{
	case 'O':
		newtio.c_cflag |= PARENB;
		newtio.c_cflag |= PARODD;
		newtio.c_iflag |= (INPCK | ISTRIP);
		break;
	case 'E':
		newtio.c_iflag |= (INPCK | ISTRIP);
		newtio.c_cflag |= PARENB;
		newtio.c_cflag &= ~PARODD;
		break;
	case 'N':
		newtio.c_cflag &= ~PARENB;
		break;
	}
	switch( nSpeed )          //set the bps
	{
	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 19200:
		cfsetispeed(&newtio, B19200);
		cfsetospeed(&newtio, B19200);
		break;
	case 115200:
		cfsetispeed(&newtio, B115200);
		cfsetospeed(&newtio, B115200);
		break;
	case 460800:
		cfsetispeed(&newtio, B460800);
		cfsetospeed(&newtio, B460800);
		break;
	default:
		cfsetispeed(&newtio, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	}

	if( nStop == 1 )                //set the 1bit stop
		newtio.c_cflag &=  ~CSTOPB;
	else if ( nStop == 2 )         //set the 2bit stop
		newtio.c_cflag |=  CSTOPB;
	newtio.c_cc[VTIME]  = 0;
	newtio.c_cc[VMIN] = 0;
	tcflush(fd,TCIFLUSH);
	if((tcsetattr(fd,TCSANOW,&newtio))!=0)
	{
		perror("com set error");
		return -1;
	}
	printf("Current serial speed is %d\n",nSpeed);
	return 0;
}

代码中给出了可以设置成阻塞和非阻塞的操作。

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