seri.c

Linux 下 C 库及常用 系统调用的使用事例

#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>
#include "seri.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;
}

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  |=  CLOCAL | 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_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 )
	{
	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, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	}
	if( nStop == 1 )
		newtio.c_cflag &=  ~CSTOPB;
	else if ( nStop == 2 )
	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("set done!\n");
	return 0;
}

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_NOCTTY|O_NDELAY);
		if (-1 == fd){
			perror("Can't Open Serial Port");
			return(-1);
		}
	}
	else if(comport==2)
	{	fd = open( "/dev/ttyS1", O_RDWR|O_NOCTTY|O_NDELAY);
		if (-1 == fd){
			perror("Can't Open Serial Port");
			return(-1);
		}
	}
	else if (comport==3)
	{
		fd = open( "/dev/ttyS2", O_RDWR|O_NOCTTY|O_NDELAY);
		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;
}