break loop with 'q'

Altera_Forum · ‎06-21-2005

Hello,

this may be a very beginner question, but I cannot get ahead.

I have a loop wich should be performed until the user presses 'q'. I tried with getchar() but it seems that getchar() waits for a return and my loop is not performed anymore. So I'm looking for a command which is not waiting for a return, or maybe a command who tells me if the uart buffer is empty or not.

Thank you for each suggestion, Ralf

do
{
  printf( "do something" );
} while( getchar() != &#39;q&#39; );

Altera_Forum · ‎06-21-2005

This happens because the default STDIN is blocking; it waits for an input before returning a value. To make the system do what you want you must make it a non-blocking call. If you are using the 5.0 release of Nios II you can use the fcntl call and change STDIN to non blocking (O_NONBLOCK flag). If you are using an earlier release, you can change the flags directly or create a new file handle for the serial line and create to be non-blocking.

Hope this helps.

Michael

Altera_Forum · ‎06-22-2005

Thank you very much, works fine now.

My code:

int32 KeyPressed( void )
{
  int32 key = -1;
  int32 flags;
  
  /* save flags */
  flags = fcntl( fileno(stdin), F_GETFL );
  
  /* set non blocking */
  if( ! fcntl( fileno(stdin), F_SETFL, flags | O_NONBLOCK ) );
  {
    key = getchar();
  }
  
  /* restore flags */
  fcntl( fileno(stdin), F_SETFL, flags );
  
  return( key );
}

Altera_Forum · ‎01-26-2010

Hi,

This code works with Quartus II 9.0 using the JTAG uart but failed when I use an UART core.

Have you an idea to allow non-blocking with the UART corre from ALTERA ??