Serial Port Programming

QNX DEVELOPERS Realtime and Embedded
1

Hi All,

I am doing the serial port testing under QNX 6.2.1B , I wrote and ran the following code but nothing can be seen from the serial output.

I would be very appreciated if any suggestion and help.

Regards,
Shilunz

int main(void)
{
int data = 0, fd, error;
int i,j,n,sec;
struct termios oldtio, newtio;

char buf[255];                       //buffer for where data is put
speed_t speed;


//if((fd = open ("/dev/ser2", O_RDWR|O_NOCTTY)) == -1)
if((fd = open ("/dev/ser1", O_RDWR |O_NOCTTY )) == -1)
{    
 fprintf(stderr, "Error with open() on /dev/ser1.  Make sure exists.\n");
 perror (NULL);
 exit(EXIT_FAILURE);
}


tcgetattr(fd,&oldtio); // save current port settings 
     
oldtio.c_cflag &= ~CSIZE;
oldtio.c_cflag |= CS8;
oldtio.c_cflag &=~CSTOPB; //1 stop   
oldtio.c_cflag &=~PARENB; //no parity

oldtio.c_cflag &=~IHFLOW; //no handshake
oldtio.c_cflag &=~OHFLOW; //no handshake  
    
oldtio.c_cflag |= CLOCAL | CREAD;
   
oldtio.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);      //raw;
//no sw handshake
oldtio.c_iflag &= ~(IXON | IXOFF );
//raw
oldtio.c_oflag &= ~OPOST;
    
    
tcflush(fd, TCIFLUSH);

//speed setting
speed=600;
//speed=38400;
cfsetispeed( &oldtio, speed);
cfsetospeed( &oldtio, speed);
tcsetattr(fd,TCSANOW,&oldtio);
    
    
sec=60;
while(sec--)
{
    	for(i=0;i<255;i++)
		buf[i]=0xff;
	  	
	
	n=write(fd, buf,i);
	if(n<0)
		printf(" Write Err!\n");
else
	printf(" Written :%d \n",n);
				
	sleep(1);
}


close(fd);

return (1);

}

2

Hi All,

I am doing the serial port testing under QNX 6.2.1B , I wrote and ran the following code but nothing can be seen from the serial output.

I would be very appreciated if any suggestion and help.

Regards,
Shilunz

int main(void)
{
int data = 0, fd, error;
int i,j,n,sec;
struct termios oldtio, newtio;

char buf[255];                       //buffer for where data is put
speed_t speed;


//if((fd = open ("/dev/ser2", O_RDWR|O_NOCTTY)) == -1)
if((fd = open ("/dev/ser1", O_RDWR |O_NOCTTY )) == -1)
{    
 fprintf(stderr, "Error with open() on /dev/ser1.  Make sure exists.\n");
 perror (NULL);
 exit(EXIT_FAILURE);
}


tcgetattr(fd,&oldtio); // save current port settings 
     
oldtio.c_cflag &= ~CSIZE;
oldtio.c_cflag |= CS8;
oldtio.c_cflag &=~CSTOPB; //1 stop   
oldtio.c_cflag &=~PARENB; //no parity

oldtio.c_cflag &=~IHFLOW; //no handshake
oldtio.c_cflag &=~OHFLOW; //no handshake  
    
oldtio.c_cflag |= CLOCAL | CREAD;
   
oldtio.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);      //raw;
//no sw handshake
oldtio.c_iflag &= ~(IXON | IXOFF );
//raw
oldtio.c_oflag &= ~OPOST;
    
    
tcflush(fd, TCIFLUSH);

//speed setting
speed=600;
//speed=38400;
cfsetispeed( &oldtio, speed);
cfsetospeed( &oldtio, speed);
tcsetattr(fd,TCSANOW,&oldtio);
    
    
sec=60;
while(sec--)
{
    	for(i=0;i<255;i++)
		buf[i]=0xff;
	  	
	
	n=write(fd, buf,i);
	if(n<0)
		printf(" Write Err!\n");
else
	printf(" Written :%d \n",n);
				
	sleep(1);
}


close(fd);

return (1);

}

3

I have personnaly never used O_NOCTTY, not sure of it’s effect here.

What does write() returns.

If at the other end of the serial port you have a terminal program (qtalk, hyperterminal… ) it is unlikely you will see the 0xff.

You should also check return value of tcsetattr.