linux基础复习（7）串口应用开发

B115200);

cfsetospeed(newtio, B115200);

break;

case 460800:

cfsetispeed(newtio, B460800);

cfsetospeed(newtio, B460800);

break;

default:

cfsetispeed(newtio, B9600);

cfsetospeed(newtio, B9600);

break;

}

/*设置停止位*/

if( nStop == 1 )

newtio.c_cflag = ~CSTOPB;

else if ( nStop == 2 )

newtio.c_cflag |= CSTOPB;

/*设置等待时间和最小接收字符*/

newtio.c_cc[VTIME] = 0;

newtio.c_cc[VMIN] = 0;

/*处理未接收字符*/

tcflush(fd,TCIFLUSH);

/*激活新配置*/

if((tcsetattr(fd,TCSANOW,newtio))!=0)

{

perror(com set error);

return -1;

}

printf(set done!\n);

return 0;

}

[b]串口使用详解[/b]

在配置完串口的相关属性后，就可对串口进行打开，读写操作了。其使用方式与文件操作一样，区别在于串口是一个终端设备。

[b]打开串口[/b]

fd = open( /dev/ttyS0, O_RDWR|O_NOCTTY|O_NDELAY);

Open函数中除普通参数外，另有两个参数O_NOCTTY和O_NDELAY。

O_NOCTTY: 通知linix系统，这个程序不会成为这个端口的控制终端。

O_NDELAY: 通知linux系统不关心DCD信号线所处的状态(端口的另一端是否激活或者停止)。

然后，恢复串口的状态为阻塞状态，用于等待串口数据的读入。用fcntl函数：

fcntl(fd, F_SETFL, 0);

接着，测试打开的文件描述府是否引用一个终端设备，以进一步确认串口是否正确打开。

isatty(STDIN_FILENO);

串口的读写与普通文件一样，使用read,write函数。

read(fd,buff,8);

write(fd,buff,8);

实例

#i nclude stdio.h>

#i nclude string.h>

#i nclude sys/types.h>

#i nclude errno.h>

#i nclude sys/stat.h>

#i nclude fcntl.h>

#i nclude unistd.h>

#i nclude termios.h>

#i nclude stdlib.h>

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;

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

printf(open ttyS0 .....\n);

}

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

printf(open ttyS1 .....\n);

}

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);

}

else

printf(open ttyS2 .....\n);

}

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 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,1