FreeBSD kernels typically come prepared to search for four serial
ports, known in the PC-DOS world as COM1:, COM2:,
COM3:, and COM4:. FreeBSD can presently also handle
``dumb'' multiport serial interface cards, such as the Boca Board
1008 and 2016 (please see the manual page sio(4) for kernel
configuration information if you have a multiport serial card). The
default kernel only looks for the standard COM ports, though.
To see if your kernel recognizes any of your serial ports, watch for
messages while the kernel is booting, or use the
/sbin/dmesg command to replay the kernel's boot messages. In
particular, look for messages that start with the characters sio.
Hint: to view just the messages that have the word sio, use the
command:
/sbin/dmesg | grep 'sio'
For example, on a system with four serial ports, these are the serial-port specific kernel boot messages:
sio0 at 0x3f8-0x3ff irq 4 on isa
sio0: type 16550A
sio1 at 0x2f8-0x2ff irq 3 on isa
sio1: type 16550A
sio2 at 0x3e8-0x3ef irq 5 on isa
sio2: type 16550A
sio3 at 0x2e8-0x2ef irq 9 on isa
sio3: type 16550A
If your kernel does not recognize all of your serial ports, you will probably need to configure a custom FreeBSD kernel for your system.
Please see the BSD System Manager's Manual chapter on ``Building
Berkeley Kernels with Config'' [the source for which is in
/usr/src/share/doc/smm] and ``FreeBSD Configuration
Options'' [in /sys/conf/options and in
/sys/arch/conf/options.arch, with
arch for example being i386] for more
information on configuring and building kernels. You may have to
unpack the kernel source distribution if have not installed the system
sources already (srcdist/srcsys.?? in FreeBSD 1.1,
srcdist/sys.?? in FreeBSD 1.1.5.1, or the entire source
distribution in FreeBSD 2.0) to be able to configure and build
kernels.
Create a kernel configuration file for your system (if you have not
already) by cding to /sys/i386/conf. Then, if you are
creating a new custom configuration file, copy the file GENERICAH (or
GENERICBT, if you have a BusTek SCSI controller on FreeBSD 1.x) to
YOURSYS, where YOURSYS is the name of your system, but in
upper-case letters. Edit the file, and change the device lines:
device sio0 at isa? port "IO_COM1" tty irq 4 vector siointr
device sio1 at isa? port "IO_COM2" tty irq 3 vector siointr
device sio2 at isa? port "IO_COM3" tty irq 5 vector siointr
device sio3 at isa? port "IO_COM4" tty irq 9 vector siointr
You can comment-out or completely remove lines for devices you do not
have. If you have a multiport serial board, such as the Boca Board
BB2016, please see the sio(4) man page for complete information
on how to write configuration lines for multiport boards. Be careful
if you are using a configuration file that was previously used for a
different version of FreeBSD because the device flags have changed
between versions.
Note that port "IO_COM1" is a substitution for port 0x3f8,
IO_COM2 is 0x2f8, IO_COM3 is 0x3e8, and
IO_COM4 is 0x2e8, which are fairly common port addresses for
their respective serial ports; interrupts 4, 3, 5, and 9 are fairly
common interrupt request lines. Also note that regular serial ports
cannot share interrupts on ISA-bus PCs (multiport boards have
on-board electronics that allow all the 16550A's on the board to share
one or two interrupt request lines).
When you are finished adjusting the kernel configuration file, use the
program config as documented in ``Building Berkeley Kernels with
Config'' and the config(8) manual page to prepare a kernel
building directory, then build, install, and test the new kernel.