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Date:      Thu, 22 Jun 2006 09:28:28 -0600
From:      "Andrew Falanga" <af300wsm@gmail.com>
To:        freebsd-questions@freebsd.org
Subject:   Serial programming on FreeBSD 6.0 RELEASE
Message-ID:  <340a29540606220828i500905afq6d1ff81cf095cf88@mail.gmail.com>
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Hello,

I've got a case where I'm writing a simply serial program to send bytes from
one system to another over a serial cable.  The program works in Linux, but
when I use it in FreeBSD nothing happens.  The program starts and, in the
case of receiving, waits for data to appear on the /dev/cuad1 port and times
out in select.  If I'm sending in FreeBSD, the send program believes it has
written all the data but nothing is received in Linux (either with running
my code on Linux or using kermit).  On FreeBSD, however, if I use kermit to
monitor the /dev/cuad1 port and send, using my code, from Linux, all 2500
packets are transmitted ok.  Also, when sending from Linux and receiving in
FreeBSD, the FreeBSD machine show silo and tty-level interrupt errors.  The
man page for sio describes that as problems in the interrupt handler, for
silo overflows, and that data arrived faster than the application could
process (for the tty-level overflows).

What am I doing wrong?  What is it that Kermit does to allow data being read
from the /dev/cuad1 device that I'm not?  I've been looking over the kermit
sources but to be honest, before Thursday of last week, I'd never programmed
for serial ports before let alone having any knowledge of termios.
Therefore, I'm looking at a very steep learning curve.  Please look over my
ctor for the serial line class that is in my code.  After much debugging,
I'm convinced that my problem is in how I'm configuring my port.

sline::sline( std::string d, int opm ) : dev( d ), opMode( opm )
{
   memset( &oldSettings, 0, sizeof( oldSettings ) );
   memset( &ioPort, 0, sizeof( ioPort ) );
   memset( recvBuf, 0, PACKETSIZE );
   memset( &timeout, 0, sizeof( timeout ) );

   FD_ZERO( &incoming );

   timeout.tv_sec = TIMEOUT_SEC;
   timeout.tv_usec = TIMEOUT_USEC;

   // create the packet
   char asciiPrtChars = 32; // first printable ascii character in decimal
   for( int i = 0; i < PACKETSIZE; i++ ) {
      packet[i] = asciiPrtChars++;
      if( asciiPrtChars == 127 ) // 127 is the delete character
         asciiPrtChars = 32;
   }

   // on the systems this code was meant to compile, LINUX and FreeBSD
   // O_NDELAY and O_NONBLOCK are the same, however, this is not always
   // true
   fd = open( dev.c_str(), O_RDWR | O_NOCTTY | O_NDELAY );
   if( fd < 0 )
      throw init();

   tcgetattr( fd, &oldSettings );
   tcgetattr( fd, &ioPort );

#ifdef DEBUG
   COUT << "Current input speed is " << cfgetispeed( &ioPort ) << ENDL;
   COUT << "Current output speed is " << cfgetospeed( &ioPort ) << ENDL;
#endif

#if 0
   if( opMode == OPMODE_WRITE ) {
      if( fcntl( fd, F_SETFL, 0 ) < 0 ) {
         perror( "fcntl" );
         throw init();
      }
   } else {
      if( fcntl( fd, F_SETFL, FNDELAY ) < 0 ) {
         perror( "fcntl" );
         throw init();
      }
      FD_SET( fd, &incoming );
   }
#endif

#if 0
   // configure control field, this should configure for 8N1
   // first, disable flow control (may have to put it back in)
   // ioPort.c_cflag &= ~CRTSCTS;
   ioPort.c_cflag |= CRTSCTS | CLOCAL | CREAD;
   ioPort.c_cflag &= ~PARENB;
   ioPort.c_cflag &= ~CSTOPB;
   ioPort.c_cflag &= ~CSIZE;
   ioPort.c_cflag |= CS8;

   // configure local field, setting to RAW mode
   ioPort.c_lflag |= ~( ICANON | ECHO | ECHOE | ISIG );

   // configure the input field, setting to ignore parity errors
   // and disable software flow control
   ioPort.c_iflag |= IGNPAR;
   ioPort.c_iflag &= ~( IXON | IXOFF | IXANY );

   // configure output field, setting to RAW
   ioPort.c_iflag &= ~OPOST;
#endif /* end of if 0 */

   // configure for raw data transfer
   cfmakeraw( &ioPort );

   // set VMIN and VTIME parameters in c_cc array
   ioPort.c_cc[VMIN] = PACKETSIZE;
   ioPort.c_cc[VTIME] = 0;

   if( cfsetispeed( &ioPort, BAUDRATE ) < 0 ) {
      perror( "cfsetispeed" );
      throw init();
   }

   if( cfsetospeed( &ioPort, BAUDRATE ) < 0 ) {
      perror( "cfsetospeed" );
      throw init();
   }

   COUT << "flushing dev: " << dev << ENDL;
   if( tcflush( fd, TCIOFLUSH ) < 0 ) {
      perror( "tcflush" );
      throw init();
   }

   COUT << "Setting new parameters to: " << dev << ENDL;
   if( tcsetattr( fd, TCSANOW, &ioPort ) < 0 ) {
      perror( "tcsetattr" );
      throw init();
   }

#if 0
   if( ioctl( fd, TIOCMGET, &portStatus ) < 0 ) {
      perror( "ioctl - get" );
      throw init();
   }

   // I believe we want to clearn the DCD bit
   portStatus &= ~TIOCM_DTR;

   if( ioctl( fd, TIOCMSET, &portStatus ) < 0 ) {
      perror( "ioctl - set" );
      throw init();
   }
#endif /* removed for debugging, still not sure I need it */

   if( fcntl( fd, F_SETFL, FNDELAY | O_NONBLOCK ) < 0 ) {
      perror( "fcntl" );
      throw init();
   }

#ifdef DEBUG
   COUT << "New input speed is " << cfgetispeed( &ioPort ) << ENDL;
   COUT << "New output speed is " << cfgetospeed( &ioPort ) << ENDL;
#endif
} // end of sline ctor

Thanks for you help,
Andy

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