『高分』如何实现串口发送数据同时处理接收数据（C/C++）

[zl198183]

现已完成串口的单工的发送和读取，源代码如下：

#include <stdio.h>
#include <fcntl.h> 
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/io.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <termios.h>
#include <sys/time.h>
#include <errno.h>



unsigned char ch_read(int fd);
int asy_open(char *Port, int Baud);

#define  DataTimeout     0
#define  UART_DEBUG

/* Main program */

static void useage()
{
	printf("uart test for 2410--------------------\n");
	printf("brate:115200\n");
	printf("example:\n");
	printf("uart3 send--------:  #uarttest -3 -s  \n");
	printf("uart3 receive------:  #uarttest -3 -r  \n");
}







int main(int argc, char **argv)
{
	int fd;
	char portname[15];
	int e;
	unsigned char ch;
	char buf[20] = "hello world!\n";
	char rvbuf[100];
	char rv_Pos;
	int ret;
	int i,n,recvbytes,flag;	

	struct timeval timeout;
   
	timeout.tv_sec = 0;
	timeout.tv_usec = 0;
	
	if(argc!=3)
	{
		useage();
		return -1;
	}
	sprintf(portname,"/dev/ttyS%d",argv[1][1]-49);
	fd = asy_open(portname,B115200);  
	if(argv[2][1]=='s')
	{
		while(1)
		{     
			write(fd,buf,strlen(buf));
			sleep(1);
		}
		return 0;
	}
	printf("read-------------\n");
	rv_Pos=0;
	/*
	while(1){
		FD_ZERO (&rset);
		if (fd >= 0)FD_SET (fd, &rset);

	        e = select (fd + 1, &rset, NULL, NULL, &timeout);

	        if (e > 0){
        	        if (fd >= 0 && FD_ISSET (fd, &rset)){
         		    	FD_CLR(fd, &rset);
				//ret = ch_read(fd);
				read(fd,&ch,1);
				//if(ret > 0)
				printf("ch = %x\n",ch);
			}
		}
	}
	*/
	memset(rvbuf,0,100);
	while(1)
	{
		//n=read(fd,&ch,1);
		recvbytes=0;
		ioctl(fd, FIONREAD, &recvbytes);
		//if there are some chars in the input buffer, then receive them.
		if(recvbytes>0)
		{
			flag=1;
			while(1)				
			{	
				n=read(fd,&ch,1);		
				if(n<0)
				{
				//printf("Serial COM receiving data error!\n");
					if(errno==EAGAIN)//Resource temporarily unavailable
						break;//break from the while loop
					else
						perror("read com error");
				}
				else if(n>0)
				{

					if((rv_Pos+1)>100)
					{
						printf("1The input buffer is overflowed!\n");
						rvbuf[rv_Pos]='\0';
						printf(rvbuf);
						printf("\n");
						rv_Pos=0;
					}
					else
					{
						rvbuf[rv_Pos]=ch;
						rv_Pos++;
					}
				}
				else
				{
					//rvbuf[rv_Pos]='\0';
					//printf(rvbuf);
					//printf("\n");
					//rv_Pos=0;
					break;
				}			
			}		
		}
		if((recvbytes==0)&&(flag==1))
		{
			rvbuf[rv_Pos]='\0';
			flag=0;
			printf(rvbuf);
			printf("\n");
			rv_Pos=0;
		}
	}
	return 0;
}




/* Char processing */
/*
unsigned char ch_read(int fd)
{	
	unsigned char ch,temp1,buf[10] = {0};
	int ret,i;

	ret = read(fd,&ch,1);
	if(!ret || ch != 0x55)return 0;
	fprintf(stderr,"ch = %x\n",ch);

	ret = read(fd,&ch,1);
	if(!ret || ch != 0x55)return 0;
	fprintf(stderr,"ch = %x\n",ch);

	ret = read(fd,&ch,1);
	if(!ret)return 0;
	fprintf(stderr,"ch = %x\n",ch);

	temp1 = ch;
	ret = read(fd,&ch,1);
	if(!ret)return 0;
	fprintf(stderr,"ch = %x\n",ch);
	if((temp1 + ch) != 0xff)return 0;

//	if((ch == 0x22) || (ch == 0x13) || (ch == 0x43) || (ch == 0x23))
		return temp1;
	

}*/


/* Uart open fuction */

int asy_open(char *Port, int Baud)
{
	struct termio SerialParameters;
	int i, fd;

	//We want to open the port in nodelay mode, so we are informed if the
	// port cannot be opened. 
	if ((fd = open (Port, O_RDWR | O_NDELAY)) == -1) {
		#ifdef UART_DEBUG
		fprintf (stderr, "asy_open: Cannot open port %s\n", Port);
		#endif
	return -1;
	}

	// Now change the rest of the parameters - non-canonical input, etc. 
	if (ioctl (fd, TCGETA, &SerialParameters) == -1) {
		#ifdef UART_DEBUG
		fprintf (stderr, "asy_open: Cannot ioctl (get) on port %s. Errno = %d\n", Port, errno);
		#endif
		return -1;
	}

	SerialParameters.c_cflag = Baud | CS8 | CLOCAL | CREAD | HUPCL;
	SerialParameters.c_lflag &= ~ICANON;

	SerialParameters.c_lflag = 0;
	SerialParameters.c_oflag = 0;
	SerialParameters.c_iflag = IGNBRK | IGNPAR;
	for (i = 0; i < NCC; i++)
		SerialParameters.c_cc[i] = (unsigned char) 0;
	SerialParameters.c_cc[VMIN] = (unsigned char) 0;
	SerialParameters.c_cc[VTIME] = (unsigned char) DataTimeout;

	if(ioctl (fd, TCSETA, &SerialParameters) == -1) {
		#ifdef UART_DEBUG
		fprintf (stderr, "asy_open: Cannot ioctl (set) on port %s. Errno = %d\n", Port, errno);
		#endif
		return -1;
	}

	return fd;
}

如何实现当串口发送数据时，如果有数据进来先读取串口数据并显示？

[cceczjxy]

实际上,串口的速率很慢的.1ms最多也不过10来个字节.但你1ms能读写可能上百次.所以,你的读写过程可以同时进行,
即在写前判断一下有没有数据要读.有就读出来处理就行了.

[kingwoo]

你这个程序只能写或者只能读啊
要同时读写用select吧

[zl198183]

如果用select应该怎么写？
初学，不明白！
哪位指点一下