QNX serial port problem need help

Hi all,

I am trying to read a word form the serial port. so I have connected two PC one running QNX with my C code and the other windows xp with hyperterminal. I am able to read characters, but not words. So here is the code I am trying.

#include <fcntl.h>
#include <stdio.h>
#include <termios.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#define SPEED B9600
#define PORT “/dev/ser1”

int main()
int fd;
struct termios options;
struct termios org_port_options;
int r,i=0;
char buff[255];
char sCmd[254];
int n;
int len;

//fd = open(PORT, O_RDWR | O_NOCTTY | O_NDELAY); 
fd = open(PORT, O_RDWR);
if(fd == -1)
	printf("Can not open the port");
	return 0;
tcgetattr(fd, &org_port_options);  	// Get the current port settings
options = org_port_options;		// save the port settings

printf("\norg_options = %d",options.c_cflag);	//test

/* Initialize the Port */
cfsetispeed(&options, SPEED);	  // Input Baud Rate - 9600
cfsetospeed(&options, SPEED);	 // Output Baud Rate - 9600

options.c_cflag |= CLOCAL;	   // Local line - Do not change the owner 
options.c_cflag |= CREAD;	    // Enable receiver
options.c_cflag |= PARENB; 	    // parity - enabled
options.c_cflag &= ~PARODD; 	 // Odd parity - even
options.c_cflag &= ~CSTOPB; 	  // stop bit - 1
options.c_cflag &= ~CSIZE;  	    // bit mask for data bits
//options.c_cflag &= ~CNEW_RTSCTS;	// hardware flow control-disable   
options.c_cflag |= CS7;		       // data bits - 7

/* Initialize the Terminal */
options.c_lflag &= ~ECHO;    	    // Echo the Terminal screen - off
options.c_lflag &= ~ICANON;	   // Canonical Input else raw - disable

options.c_iflag &= ~INPCK;	     // Parity Check - disable
    options.c_iflag &= ~IGNBRK; 	    // Parity Errors - Ignore 
options.c_iflag &= ~PARMRK; 	    // Mark Parity Errors - disable
options.c_iflag &= ~ISTRIP; 	      // Strip Parity bits - disable
options.c_iflag &= ~IXON;	      // Software outgoing flow control - disable
options.c_iflag &= ~IXOFF;	       // Software incoming flow control - disable	      	
options.c_oflag &= ~OPOST;	     // Post process output (not set = raw output)
tcsetattr(fd, TCSANOW, &options);   // make changes on the Port
printf(" options = %d",options.c_cflag);
fcntl(fd, F_SETFL, 0);  //FNDELAY);

//printf(" buff = %s\n",buff);
    sCmd[0] = 0x41;
sCmd[1] = 0x42;
sCmd[2] = 0x43;
sCmd[3] = 0x00;;	// keystroke input from user.
len = strlen(sCmd);
sCmd[len] = 0x0d; // stick a <CR> after the command
sCmd[len+1] = 0x00; // terminate the string properly

while(i < 20)
	r = read(fd, &buff, '\r');
	buff[r] = '\0';
	if(r > 0) 
		printf(" ");
		printf(" String = %s\n", buff);

		n = write(fd, sCmd, strlen(sCmd));
		if (n < 0) {
			fputs("write failed!\n", stderr);
			return 0;


return 0;


Please let me know any changes and improvements I have to make.
Thank you.

If you are able to read characters your able to read words… :slight_smile:
Anyway I think you should check the way your are calling read function.

The prototype is : ssize_t read( int fildes, void* buf, size_t nbyte ) as you see in docs.

Juan Manuel

The hardware interface to the computer consists of a Universal Asynchronous Receiver/Transmitter (UART) for each serial port. But i dont know how to connected to a serial port? I would like to connect/login to a qnx system through a serial connection to be able to execute files.

I don’t think that QNX supports that natively. So you need an application on the other machine that communicates with the serial interface too - and forwards the received requests to the system. May be a small proxy that forwards the data between the serial interface and a local SSH server would be a solution.

I can’t tell who’s right here. Of course you can connect to a QNX system via a serial link and login and execute programs. You have to set things up using tinit so that the login will appear on the serial link. Is that what adenjhon is asking?