linux串口编程

#include     <stdio.h>      /*标准输入输出定义*/
#include     <stdlib.h>     /*标准函数库定义*/
#include     <unistd.h>     /*Unix标准函数定义*/
#include     <sys/types.h>  /**/
#include     <sys/stat.h>   /**/
#include     <fcntl.h>      /*文件控制定义*/
#include     <termios.h>    /*PPSIX终端控制定义*/
#include     <errno.h>      /*错误号定义*/


/***@brief  设置串口通信速率
*@param  fd     类型 int  打开串口的文件句柄
*@param  speed  类型 int  串口速度
*@return  void*/

#define FALSE -1
#define TRUE 0

int speed_arr[] = { B38400, B19200, B9600, B4800, B2400, B1200, B300,
	    B38400, B19200, B9600, B4800, B2400, B1200, B300, };
int name_arr[] = {38400,  19200,  9600,  4800,  2400,  1200,  300,
	    38400,  19200,  9600, 4800, 2400, 1200,  300, };
void set_speed(int fd, int speed)
{
  int   i;
  int   status;
  struct termios   Opt;
  tcgetattr(fd, &Opt);
  for ( i= 0;  i < sizeof(speed_arr) / sizeof(int);  i++)
   {
   	if  (speed == name_arr[i])
   	{
   	    tcflush(fd, TCIOFLUSH);
    	cfsetispeed(&Opt, speed_arr[i]);
    	cfsetospeed(&Opt, speed_arr[i]);
    	status = tcsetattr(fd, TCSANOW, &Opt);
    	if  (status != 0)
            perror("tcsetattr fd1");
     	return;
     	}
   tcflush(fd,TCIOFLUSH);
   }
}
/**
*@brief   设置串口数据位，停止位和效验位
*@param  fd     类型  int  打开的串口文件句柄*
*@param  databits 类型  int 数据位   取值 为 7 或者8*
*@param  stopbits 类型  int 停止位   取值为 1 或者2*
*@param  parity  类型  int  效验类型 取值为N,E,O,,S
*/
int set_Parity(int fd,int databits,int stopbits,int parity)
{
	struct termios options;
 if  ( tcgetattr( fd,&options)  !=  0)
  {
  	perror("SetupSerial 1");
  	return(FALSE);
  }
  options.c_cflag &= ~CSIZE;
  switch (databits) /*设置数据位数*/
  {
  	case 7:
  		options.c_cflag |= CS7;
  		break;
  	case 8:
		options.c_cflag |= CS8;
		break;
	default:
		fprintf(stderr,"Unsupported data size\n");
		return (FALSE);
	}
  switch (parity)
  	{
  	case 'n':
	case 'N':
		options.c_cflag &= ~PARENB;   /* Clear parity enable */
		options.c_iflag &= ~INPCK;     /* Enable parity checking */
		break;
	case 'o':
	case 'O':
		options.c_cflag |= (PARODD | PARENB);  /* 设置为奇效验*/
		options.c_iflag |= INPCK;             /* Disnable parity checking */
		break;
	case 'e':
	case 'E':
		options.c_cflag |= PARENB;     /* Enable parity */
		options.c_cflag &= ~PARODD;   /* 转换为偶效验*/
		options.c_iflag |= INPCK;       /* Disnable parity checking */
		break;
	case 'S':
	case 's':  /*as no parity*/
		options.c_cflag &= ~PARENB;
		options.c_cflag &= ~CSTOPB;
		break;
	default:
		fprintf(stderr,"Unsupported parity\n");
		return (FALSE);
		}
  /* 设置停止位*/
  switch (stopbits)
  	{
  	case 1:
  		options.c_cflag &= ~CSTOPB;
		break;
	case 2:
		options.c_cflag |= CSTOPB;
		break;
	default:
		fprintf(stderr,"Unsupported stop bits\n");
		return (FALSE);
	}
  /* Set input parity option */
  if (parity != 'n')
  		options.c_iflag |= INPCK;
    options.c_cc[VTIME] = 150; // 15 seconds
    options.c_cc[VMIN] = 0;

  tcflush(fd,TCIFLUSH); /* Update the options and do it NOW */
  if (tcsetattr(fd,TCSANOW,&options) != 0)
  	{
  		perror("SetupSerial 3");
		return (FALSE);
	}
  return (TRUE);
 }
/**
*@breif 打开串口
*/
int OpenDev(char *Dev)
{
int	fd = open( Dev, O_RDWR| O_NDELAY|O_NONBLOCK);         //| O_NOCTTY | O_NDELAY
	if (-1 == fd)
		{ /*设置数据位数*/
			perror("Can't Open Serial Port");
			return -1;
		}
	else
	return fd;

}
/**
*@breif 	main()
*/
int main(int argc, char **argv)
{
	int fd;
	char *dev ="/dev/ttyUSB0";      //注意串口名称
	fd = OpenDev(dev);
	if (fd>0)
    	set_speed(fd,19200);
	else
	{
		printf("Can't Open Serial Port!\n");
		exit(0);
	}
  	if (set_Parity(fd,8,1,'N')== FALSE)
 	{
    		printf("Set Parity Error\n");
    		exit(1);
  	}

           fd_set rfds;
           struct timeval tv;
           int retval;

           tv.tv_sec = 0;
           tv.tv_usec = 1000;

	while(1)
	{
		  FD_ZERO(&rfds);
           FD_SET(fd, &rfds);
		retval = select(fd+1, &rfds, NULL, NULL, &tv);
		if (retval <0)
               	{
			perror("select()");
		}
           	else if(FD_ISSET(fd, &rfds))
		{
			char buffer[512];
			char data[512];
			int len;
			int nread;
			memset(buffer, 0, sizeof(buffer));
			memset(data, 0, sizeof(data));
			len = 0;

			while((nread = read(fd,buffer,1))>0)
      			{
				int i;
				for(i=0;i<nread;i++)
				{
					data[len++] = buffer[i];
				}
      			}

			data[len]='\0';
			printf("%s",data);
			fflush(NULL);		//attention ! refresh data buffer,otherwise cannot see print data.

			int nByte = write(fd, data ,strlen(data));

		}
		else
		{
			//printf("time out\n");
			//sleep(0.5);
		}

	}

    close(fd);
    return 0;
}