You CANNOT mix using hardware interrupts  and going through a the serial port driver. It`s either one or the other.  You
 are disabling interrupt while writing to disk and to the screen, this is real bad because these operation can take a 
long time, and you lucking the disc controller is not using the same interrupt as the serial port ;-)

Basically your approach is all wrong.  Either you totally take control of the hardware and kill devc-8250 or you rely 
totally on the driver.  

You code should look something like

 open_port();
ssize_t rssize;
#define SIZE_BUFFER 167
char buffer[SIZE_BUFFER];
while (1 )
{
  rssize = read(fd, buffer, SIZE_BUFFER);  // this will block until SIZE_BUFFER bytes has been received, no need to use 
interrupt
  if ( rrsize != SIZE_BUFFER )
  {
	// handle error or the fact that not all data has bee received
  }
 else
 {
     printf("\n numREAD %d\n",numRead);
      /*WRITE*/
      printf("%s",buffer);
      write(outfd,buffer,SIZE_BUFFER);     //writing to file on PC/104
 }

-----Message d'origine-----
De : Avantha Jayawickreme [mailto:community-noreply@qnx.com] 
Envoyé : 17 août 2010 23:22
À : momenticsgs-community
Objet : Reading from serial port

Hey all!

I am having difficulty reading from the serial port, it is being controlled by interrupts when the data comes in, it is 
supposed to be roughly 1Hz (depends on GPS signal and stuff) I am encountering 2 problems:

1: Is that when i read using Interrupts so the serial port interrupts when the data is ready to be read, that happens 
roughly 1Hz, then after that i for some reason get like  roughly 20(give or take)  interrupts one after another which 
also reads the data (its not supposed to do this, because the program on the IMU that i am using outputs data roughly 
every 1Hz).

2: After i perform the read I noticed that the data in the serial port doesn;t get updated for some reason, and the data
 that is in the serial port is only maxed at 2048 bytes(anyone know why this is?), it only gets updated when i perform 
an InterruptWait() and corresponding InterruptUnmask() when this happens I found out that the data in the serial port 
gets refreshed 8 bytes at a time, so eventually after say 2048 - 167 *(amount of reads), the data in the serial port 
runs out and ruins my whole output.
To counteract that problem i put in a while loop (which is in the code below).
To make sure I only read when there is more then 167 bytes.

CODE: FOR READING FROM SERIAL PORT

while(1){

         InterruptWait( 0, NULL );
   //THE LOOP BELOW IS WHAT I USE TO MAKE SURE THERE IS MORE THEN 167 BYTES BEFORE I READ     
   while (tcischars(fd)<(167))
          {
             InterruptUnmask( IRQ, intr_id );
             InterruptWait(0,NULL);
          }
      numRead = read(fd, buffer, SIZE_BUFFER);
      printf("\n numREAD %d\n",numRead);
      /*WRITE*/
      printf("%s",buffer);
      write(outfd,buffer,SIZE_BUFFER);     //writing to file on PC/104

      /* Reenable this interrupt since writing is finished */
     InterruptUnmask( IRQ, intr_id );

      }


CODE FOR SETTING UP SERIAL PORT
The IMU has to be read at 9600baud No flow contorl no parity and read 8 Bits at a time (ASCII)

int open_port(void)
{
int fd; /* File descriptor for the port */
      struct termios termios_p; /*termios structure*/
      fd = open("/dev/ser1", O_RDONLY | O_NOCTTY );
  if (fd == -1)

      {
            perror("open_port: Unable to open /dev/ser1 - ");
            return 0;
      }
      else
            printf ("port opened\n");
      tcgetattr(fd, &termios_p);                /*read in the current settings*/
      cfsetispeed(&termios_p, BAUD_RATE);       //set input baud
      cfsetospeed(&termios_p, BAUD_RATE);       //set output baud
      termios_p.c_cflag &= ~PARENB;       //no parity bit (error checking bit)
      termios_p.c_cflag &= ~CSIZE;
      termios_p.c_cflag |= CS8;           //set number of...