On the H3 development board to run Linux, want to use he read a serial port information, such as serial port tool sends abcde
But read out the contents of the first read the first loss, a second read out entirely, the third time without a, 4 times and read out, all the time cycle,
Please tell me what's the problem?

The HTML code is as follows:

 # include & lt; Errno. H> 
# include & lt; fcntl.h> 
# include & lt; stdio.h> 
# include & lt; stdlib.h> 
# include & lt; string.h> 
# include & lt; Termios. H> 
# include & lt; unistd.h> 
# include & lt; Iostream> 

using namespace std; 

Int set_interface_attribs (int fd, int speed) 
{
Struct termios tty. 

If (tcgetattr (fd, & amp; Tty) & lt; 0 {
Printf (" the Error from tcgetattr: % s \ n ", the strerror (errno)); 
return -1; 
} 

Cfsetospeed (& amp; Tty (speed_t) speed); 
Cfsetispeed (& amp; Tty (speed_t) speed); 

Tty. C_cflag |=(CLOCAL | CREAD);/* ignore modem controls */
Tty. C_cflag & amp;=~ CSIZE; 
Tty. C_cflag |=CS8 gives;/* 8-bit characters */
Tty. C_cflag & amp;=~ PARENB;/* no parity bit */
Tty. C_cflag & amp;=~ CSTOPB;/* only need 1 stop bit */
Tty. C_cflag & amp;=~ CRTSCTS;/* no hardware flowcontrol */

/* setup for non - canonical mode */
Tty. C_iflag & amp;=~ (IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON); 
Tty. C_lflag & amp;=~ (ECHO | ECHONL | ICANON | ISIG | IEXTEN); 
Tty. C_oflag & amp;=~ OPOST; 

/* the fetch bytes as they become available */
Tty. C_cc [VMIN]=1; 
Tty. C_cc [VTIME]=1; 

If (tcsetattr (fd, TCSANOW, & amp; Tty)!=0) {
Printf (" the Error from tcsetattr: % s \ n ", the strerror (errno)); 
return -1; 
} 
return 0; 
} 

Void set_mincount (int fd, int McOunt) 
{
Struct termios tty. 

If (tcgetattr (fd, & amp; Tty) & lt; 0 {
Printf (" Error tcgetattr: % s \ n ", the strerror (errno)); 
return; 
} 

Tty. C_cc [VMIN]=McOunt? 1:0; 
Tty. C_cc [VTIME]=5;/* half second timer */

If (tcsetattr (fd, TCSANOW, & amp; Tty) & lt; 0) 
Printf (" Error tcsetattr: % s \ n ", the strerror (errno)); 
} 


Int main () 
{
Char * portname="/dev/ttyS0"; 
Int fd. 
Int wlen; 

Fd=open (portname, O_RDWR | O_NOCTTY | O_SYNC); 
If (fd & lt; 0 {
Printf (" Error opening % s: % s \ n ", portname, strerror (errno)); 
return -1; 
} 
/* baudrate 9600, 8 bits, no parity, 1 stop bit */
//set_mincount (fd, 0);/* set to pure timed read */
Set_interface_attribs (fd, B115200); 
Char buf [64]. 
Int rdlen=0; 
/* simple noncanonical input */
Do {

Memset (buf, 0, sizeof (buf)); 
Rdlen=read (fd, buf, sizeof (buf)); 
If (rdlen & gt; 0 {
cout<" Rdlen: "& lt; } else if (rdlen & lt; 0 {
Printf (" the Error from the read: % d: % s \ n ", rdlen, strerror (errno)); 
} 
Sleep (0); 
/* reeat read to get the full message */
} the while (1); 
}