comport_old.c

一个串口通讯的c语言的例子

// 对串口的操作
#define ETX  0x03
#define STX  0x02

// 获得当前时间
long getCurrTime(){
	long currTime; 
	time( &currTime );
    //printf( "Time in seconds since UTC 1/1/70:\t%ld\n", currTime );
	return currTime;
}

//open a COM2 port :tty2a
int openPort(char *dev){
	int fd; /* File descriptor for the port */
	fd = open(dev, O_RDWR | O_NOCTTY | O_NDELAY);
	
	if (fd == -1){	// Could not open the port.
		printf("Unable to open %s port\n",dev);
		return -1;
	}
//	printf("Opened a serial port: %s\n",dev);
	return fd;
}

//close Port
void closePort(int fd){
	close(fd);
}

//read data from serial port and check data 
int readPort(int fd,unsigned char *buffer,int *length){
	int	i = 0, n = 1, len = 0, flag = 0, timeout = 0;
	unsigned char lrc = '\x00';					//unsigned char	lrc;
	long currTime1,currTime2;

//	printf("read begin .....\n");
	if ( read(fd, buffer, 1) > 0 ) {			// 读启始位‘02’
		if (buffer[0] == STX){
			printf("[%02x]", buffer[0] );
		}else{
//			printf("Error Head!\n");
			return 0;
		}
	}else{
//		printf("No data!\n");
		return 0;
	}

	currTime1=getCurrTime();
	
	for ( ; ; ) {
		if (read(fd, &buffer[n], 1) > 0 ) {
			printf("[%02x]", buffer[n] );

			fflush(stdout);

			if ( flag < 2 ) {
				len = len * 100 + (((buffer[n] & 0xf0) >> 4) * 10 + (buffer[n] & 0x0f));
				lrc ^= buffer[n];
                flag++;
				n++;
			}else if ( flag == 2 && i++ < len ){
				*length = len + 5;
				lrc ^= buffer[n];
				n++;
			}else if ( flag == 2 && i >= len ){
				if ( buffer[n] == ETX ){
					lrc ^ = buffer[n];
					flag++;
					n++;
				} else {
//					printf("\nETX not received\n" );
					return( -1 );
				}
			}else if ( flag == 3 ){
				if ( lrc != buffer[n] ) {
//					printf("2 resp LRC: %2x, cacl LRC: %02x\n", buffer[n], lrc );
					return( -2 );
				} else {
					return( len );
				}
			}
		}else {
//			printf("\nNot data\n" );
			currTime2 = getCurrTime();
//			printf("\ntime=%d-%d\n",currTime2,currTime1);
			if( (currTime2-currTime1)>timeout){
//				printf("\nTime out=%d\n", currTime2-currTime1);
//				printf("\nTime out\n" );
				return( 0 );
			}
		}
	}
}

//write to serial port
void writePort(int fd,unsigned char *buffer,int len){
	int  k;

	for ( k = 0; k < len; k++) {
//		printf("[%02x]",buffer[k]);
		while ( write(fd, buffer + k, 1) != 1 );
	}
}

int setAttr(int fdread){
	struct termio comtty;
	
	if(ioctl(fdread,TCGETA,&comtty)){
		printf("\n[ERROR]: Get tty error\n" );
		return (-1);
	}

	comtty.c_iflag = 1;
	comtty.c_oflag = 0;
	comtty.c_cflag =(B9600|CS8|CREAD|HUPCL|CLOCAL);
	comtty.c_lflag = 0;
	comtty.c_cc[VMIN]=0;
	comtty.c_cc[VTIME]=1;

	if(ioctl(fdread,TCSETA,&comtty)==-1){
		printf("\n[ERROR]: Set tty error\n" );
		return (-1);
	}
}

int setNowait(int fd){
	struct termio term_attr;
	
	if(fd<0) return -1;
	
	if(ioctl(fd,TCGETA,&term_attr)<0)
		return -1;
	
	term_attr.c_cc[VMIN]=0;
	term_attr.c_cc[VTIME]=1;
	
	if(ioctl(fd,TCSETAW,&term_attr)<0)
		return -1;
	
	return 0;
}