串口通讯question????
这是我改写别人的一个串口通讯的程序,主要是实现PC和电子秤通讯的程序.但是为什么老读不出数据呀,当我向电子秤写入02010103的时候,电子秤就应该向PC发送数据呀,为什么呢
#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>
#include<iostream>
#include<string>
#define FALSE-1
#define TRUE 0
int set_Parity(int fd,int databits,int stopbits,int parity)
{
struct termios options;
// options.c_lflag&= ~(ICANON | ECHO | ECHOE | ISIG);/*Input*/
//options.c_oflag&= ~OPOST; /*Output*/
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;
tcflush(fd,TCIFLUSH);
options.c_cc = 0; /* 设置超时15 seconds*/
options.c_cc = 10; /* Update the options and do it NOW */
if (tcsetattr(fd,TCSANOW,&options) != 0)
{
perror("SetupSerial 3");
return (FALSE);
}
return (TRUE);
}
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) {
tcflush(fd, TCIOFLUSH);
cfsetispeed(&Opt, speed_arr);
cfsetospeed(&Opt, speed_arr);
status = tcsetattr(fd, TCSANOW, &Opt);
if(status != 0) {
perror("tcsetattr fd1");
return;
}
tcflush(fd,TCIOFLUSH);
}
}
}
using namespace std;
int main(void)
{
int fd,nread,nwrite,i;
char buff;
structtermios Opt;
string a,b,c,d,line;
string cline;
fd=open("/dev/ttyS0",O_RDWR|O_NOCTTY|O_NDELAY);
if(fd<0)
{
cout<<"open serial failed"<<endl;
exit(1);
}
set_speed(fd,9600);
if(set_Parity(fd,8,2,'N')==FALSE)
{
cout<<"set parity error\n";
exit(0);
}
a=static_cast<char>(2);
b="0101";
d=static_cast<char>(3);
line=a+b+d;
cout<<line.c_str()<<endl;
// cline=line.c_str();
nwrite=write(fd,line.c_str(),9);
if(nwrite<0)
{
cout<<"send data failed"<<endl;
}
while (1) //循环读取数据
{
//fcntl(fd,F_SETFL,FNDELAY);
nread = read(fd, buff, 1);
/* printf("\nLen %d\n",nread);
buff = '\0'; */
if(nread<0)
{
cout<<"read data failed"<<endl;
exit(0);
}
cout<<nread<<endl;
}
close(fd);
}
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