RS-232, controlling the RTS pin

[Doug Carter]

I've been using a C program to control a custom radio on FreeBSD
(5.2-5.4) for some time.  This program uses the RS-232 RTS pin to
key the half duplex radio transmitter.  I am attempting to port
this program to OpenBSD 3.8.

On the OpenBSD machine the serial port (cua00) sends and receives
bytes just fine but my code to switch the RTS pin does not seem
to work.  I never see any state change on the RTS pin.  

My question is: Does OpenBSD support RTS control (not flow
control)?  If so, is the control done differently than under
FreeBSD?


The relevent C code fragments. First I call 'lockLINX' as part of
the serial port setup then call 'Transmit' and 'Receive' as
appropiate for my half duplex communicaiton:


#define LINX      "cua00"
lockLINX()
{
int error_limit = 0;
for(;;)
   {
   if(error_limit++ == 200) return(0);  // give up
   if(uu_lock(LINX) == 0)  // 0 == good lock
      {
      if((SIO_fd = open("/dev/" LINX, O_RDWR | O_FSYNC)) > 2)
         break;  // valid fd
      }
   usleep(50U * 1000U);
   }
tcgetattr(SIO_fd,&oldtio);       /* save current serial port
settings */
memset(&newtio, 0, sizeof(newtio)); /* clear struct for new port
settings */
newtio.c_ispeed      = BAUDRATE;
newtio.c_ospeed      = BAUDRATE;
newtio.c_cflag       = CLOCAL | CS8 | CREAD;
newtio.c_iflag       = IGNPAR | IGNBRK | IGNCR;
newtio.c_oflag       = 0;
newtio.c_lflag       = 0;
newtio.c_cc[VTIME]   = 2;
newtio.c_cc[VMIN]    = 0;
tcsetattr(SIO_fd,TCSANOW,&newtio);                                              
tcflush(SIO_fd, TCIFLUSH);                                                      
return(1);
}


void 
Transmit()  // set LINX RTS line high to key transmitter
{
ioctl(SIO_fd, TIOCMGET, &UART_status);
UART_status |= TIOCM_RTS;
ioctl(SIO_fd, TIOCMSET, &UART_status);
usleep(1000U);  // give the RTS line time to settle
sleep(2);
}


void 
Receive()      // set LINX RTS line low to unkey transmitter
{
ioctl(SIO_fd, TIOCMGET, &UART_status);
UART_status &= ~TIOCM_RTS;
ioctl(SIO_fd, TIOCMSET, &UART_status);
}

-- 
Doug Carter