First, make sure you have the right cable. Your modem requires a straight through cable, with no pins crossed. Any computer store should have these. Make sure you get the correct gender. Your DB25 serial port on your PC is always male. Do not confuse it with the parallel port, which is the female DB25. Hook up your modem to one of your serial ports. Consult your modem manual on how to do this.
For an internal modem, you will not need a cable. An internal modem does not need a serial port, it has one built in. All you need to do is configure it to use an interrupt that is not being used, and configure the I/O address. Consult your modem manual if you get stuck. Also, see section 8 if you need help on choosing interrupts or addresses.
Due to a bit of stupidity on IBM's part, you may encounter
problems if you want your internal modem to be on COM4. If Linux
does not detect your internal modem on COM4, you can use
setserial
and the modem will work fine. Internal modems
on COM1 - COM3 should not have any problems.
For now, make sure that nothing is using the serial port you hooked
your modem to. Check to see if there is a getty
watching it,
or that it has not been locked by another process. If there is a
getty
process running on that port, check your
/etc/inittab
file for entries using that serial port.
Comment the line out (with a "#"), and restart init
.
Do not comment any lines that contain a tty*
device, only ones
containing ttyS*
or cua*
. tty*
devices are your
virtual consoles.
Use kermit
to test the setup. For example, say your modem was
on /dev/cua3
, and it could handle 2400 bps.
You would do the following:
linux# kermit
C-Kermit 5A(188), 23 Nov 92, POSIX
Type ? or HELP for help
C-Kermit>set line /dev/cua3
C-Kermit>set speed 2400
/dev/cua3, 2400 bps
C-Kermit>c
Connecting to /dev/cua3, speed 2400.
The escape character is Ctrl-\ (ASCII 28, FS)
Type the escape character followed by C to get back,
or followed by ? to see other options.
AT
OK
<ctrl>-\-C
(Back at linux)
C-Kermit>quit
linux#
If your modem responds to AT
commands, you can assume your modem
is working correctly on the Linux side. Try dialing another modem.
If you don't like kermit
, try one of the more advanced
comm programs. Check out the section about comm programs if you
need some pointers.
For dial out use only, you can configure your modem however you want.
I like to see result codes, so I set Q0
. To set this on my modem,
I would have to preceed the register name with an AT
command.
Using kermit
or some comm program, connect to your modem and
do the following:
ATQ0
If your modem says OK
back to you, then the register is set.
Do this for each register you want to set.
I also like to see what I'm typing, so I set E1
. If your modem
has data compression capabilities, you probably want to enable them.
You may want to enable RTS/CTS handshaking.
Consult your modem manual for more help, and a full listing of option.