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本帖最后由 yff1030 于 2012-08-29 08:14 编辑
大家好！
我写了一个Linux下串口和主机通信的小程序，问题是这样的：
首先我的网络是通的，我用主机上的串口助手和Mini2440上的串口助手可以互相通信，所以硬件问题排除了。
现在，mini2440给PC发数据，PC可以收到，可是，PC给mini2440发数据，mini2440收不到。
#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>
/*******************打开串口*************************/
int open_port(int fd,int comport)
{
char *dev[]={"/dev/ttySAC0","/dev/ttySAC1","/dev/ttySAC2"};
long vdisable;
if (comport==1)
{
fd = open( "/dev/ttySAC0", O_RDWR|O_NOCTTY|O_NONBLOCK);
/*读写操作、不作为控制终端、不关心另一端口是否激活或关闭*/
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC0 .....\n");
}
else if(comport==2)
{
fd = open( "/dev/ttySAC1", O_RDWR|O_NOCTTY|O_NONBLOCK);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC1 .....\n");
}
else if (comport==3)
{
fd = open( "/dev/ttySAC2", O_RDWR|O_NOCTTY|O_NONBLOCK);
if (-1 == fd){
perror("Can't Open Serial Port");
return(-1);
}
else
printf("open ttySAC2 .....\n");
}
if(fcntl(fd, F_SETFL, 0)<0) //fcntl()设置串口的状态为阻塞状态，等待串口数据读入
printf("fcntl failed!\n");
else
printf("fcntl=%d\n",fcntl(fd, F_SETFL,0));//F_SETFL设置文件标记状态
if(isatty(STDIN_FILENO)==0) //isatty()测试打开的文件描述符是否引用一个终端设备，以进一步确认串口是否正确打开
printf("standard input is not a terminal device\n");
else
printf("isatty success!\n");
printf("fd_open=%d\n",fd);
return fd;
}
/*******************设置串口参数************************/
int set_opt(int fd,int nSpeed, int nBits, char nEvent, int nStop)
{
struct termios newtio,oldtio;
if ( tcgetattr( fd,&oldtio) != 0) //将原有的设置保存到oldio，以便程序结束后恢复
{
perror("SetupSerial 1");
return -1;
}
bzero( &newtio, sizeof( newtio ) );
newtio.c_cflag |= CLOCAL | CREAD; //本地连接和接收使能
newtio.c_cflag &= ~CSIZE; //清除数据位掩码设置
newtio.c_lflag&=~(ICANON);
newtio.c_lflag &= ~(ICANON |ISIG);
newtio.c_iflag &= ~(ICRNL|IGNCR);
switch( nBits )
{
case 7:
newtio.c_cflag |= CS7; //数据位数
break;
case 8:
newtio.c_cflag |= CS8;
break;
}
switch( nEvent )
{
case 'O': //奇校验设置
newtio.c_cflag |= PARENB;
newtio.c_cflag |= PARODD;
newtio.c_iflag |= (INPCK | ISTRIP);
break;
case 'E': //偶校验设置
newtio.c_iflag |= (INPCK | ISTRIP);
newtio.c_cflag |= PARENB;
newtio.c_cflag &= ~PARODD;
break;
case 'N': //无校验
newtio.c_cflag &= ~PARENB;
break;
}
switch( nSpeed )
{
case 2400:
cfsetispeed(&newtio, B2400); //设置输入波特率
cfsetospeed(&newtio, B2400);//设置输出波特率
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 )
//停止位设置，若停止位为1, 则清除CSTOPB，
//若停止位为2，则激活CSTOPB。
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);
//tcflush()刷清输入缓冲区或输出缓冲区
//TCIFLUSH 输入队列
if((tcsetattr(fd,TCSANOW,&newtio))!=0) //前面串口的参数设置立即生效
{
perror("com set error");
return -1;
}
printf("set done!\n");
return 0;
}
/************************主函数************************/
int main(void)
{
int fd;
int i;
int nread;
char *buff;
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);
while(1)
{
nread=read(fd,buff,255); //读串口数据
printf("nread=%d\n",nread);
if(nread>0)
{
printf("receive data is %s\n",buff);
}
else
printf("cannot receive data!\n");
sleep(2);
}
close(fd);
return 0;
}
执行结果:
open ttySAC0......
fcntl=0
isatty success!
fd_open=11;
set done!
fd=11;
nread=0
cannot receive data!
nread=0
cannot receive data!
nread=-1
cannot receive data!
nread=-1
cannot receive data!
nread=-1
cannot receive data!
nread=-1
cannot receive data!
........
求指教，为什么read函数一直读不成功？
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发表于 2012-05-18 16:51
求指教！
