>
>This is a list of the serial problems I have had on my linux system.
>Each problem is described shortly and after that is explained how I solved
>it.
>
>-----
>Problem:
>Trying to allow login on my terminal (on ttyS1 with only three wires
>(RX, TX, GND) connected). Getty 9600 /dev/ttyS1 starts and I get the
>login prompt, but the password prompt newer appears.
>
>Solved by:
>Changed the /etc/gettydefs line
>9600# B9600 CS8 # B9600 SANE -ISTRIP #S login: #9600
>to
>9600# B9600 CS8 # B9600 SANE -ISTRIP CLOCAL #S login: #9600
>
>Also can be solved by:
>Fake the serial singnals. Shortcut (pins 4 and 5), (pins 6, 8 and 20) on D25
>connector plugged to the I/O card.
>
>Question:
>What would be the proper way to solve this? Bug in kernel?
Setting CLOCAL is the correct way to solve this --- it is not a bug in
the kernel. Since you only have three wires connected, it means that
the carrier detect line was left floating, and probably floated to
ground. Thus, the /dev/ttyS1 device blocked waiting for carrier detect
to go high. The reason why the login prompt appeared is that getty
opened /dev/ttyS1 with the NODELAY flag; but when /dev/ttyS1 was
reopened for /bin/login, it did not have the NODELAY flag, and you ended
up blocking.
That's what the CLOCAL flag is for --- it indicates that the serial port
is hooked up to a local (hence CLOCAL) terminal, and so the carrier
detect line should be ignored. In general, whenever the carrier detect
line is not supported by a serial device, or if your RS-232 cable does
not support the CD wire, the CLOCAL flag should be set.
>-----
>Problem:
>Where are my Call-out-mode -serial ports (cuaX)
>
>Solved by:
> login as root
> cd /dev
> mknod cua0 c 5 64
> mknod cua1 c 5 65
> mknod cua2 c 5 66
> mknod cua3 c 5 67
> chmod ugo+rw cua?
> ln -sf cua3 modem
>
>Questions:
>When will these be created in install procedure?
Ask the person who created the install procedure (Peter MacDonald, in
the case of SLS).
>When should I use these cuaX ports?
When you're dialing out (i.e., kermit, cu, seyon, uucp, etc.).
>On my configuration ttyS3 is named ttys3 incorrectly - why?
Again, see the person who created the install procedure. Recent
versions of SLS create the serial devices using the new convention
(ttyS3). ttys3 represents an older convention, and some older install
procedures may not have switched over.
>------
>Problem:
>I got the remote logins on terminal working, but when I start X, the terminal
>session hangs. My mouse is on ttyS0, terminal on ttyS1 and modem on ttyS3.
>TtyS0 uses IRQ 4, ttyS1 and ttyS3 use IRQ 3. The cards are made in Taiwan.
>
>Solved by:
>IRQ's can't be shared by serial ports. Must configure them differently.
>Here's a list of IRQ's and their use.
>
>No. MSDOS name /dev/... Pin
>-----------------------------------------------
>IRQ 3 Com2 / Com4 ttyS1 / ttyS3 B25
>IRQ 4 Com1 / Com3 ttyS0 / ttyS2 B24
>IRQ 5 LPT2 lp2 B23
>IRQ 6 Floppy drive B22
>IRQ 7 LPT1 lp1 B21
>IRQ 9 VGA? B4
>
>If there the system hasn't a secondary parallel port, IRQ 5 is usually free.
>
>The simplest I/O cards don't let configure themselves too much. Often you
>can only select IRQ 4 or 3 to be used. This prevents from getting more than
>2 serial ports in use.
>
>To make a simple multi-I/O card co-existing with another one, you must
>change the IRQ wirings on the card. A simple 8-bit I/O card has 31 connecting
>pins on the both sides. Pin 1 is near the plate with connectors and pin 31 is
>in the other end. Side A is the component side and side B is the other one.
>
>To make the card use IRQ 5 instead of IRQ 4 you cut the folio connected to
>pin B24 and reconnect it to pin B23 (small soldering needed).
>
>Questions:
>What other possibly free IRQ's there are than IRQ 5?
IRQ 2 is also often free, although some networking cares use them.
Can I use IRQ 7 when not printing?
It's generally a bad idea to have two cards plugged in sharing an IRQ
address. It happens to work with most serial cards, but it doesn't
alwas work. You can use IRQ 7 if you don't have a parallel port plugged
into your system. If you do have a parallel port plugged in, you can
try using IRQ 7; it might work, it might not. Be sure to also make sure
that the printer works after you plug in your serial card configured to
use IRQ 7. Another alternative: If you are using the version of the
parallel printer driver that doesn't use interrupts, you can go to your
parallel port board, and disable the IRQ, thus freeing IRQ 7.
Is pin 1 nearest to the plate or is it 31?
If this is a sample PC ISA card, then A1 is the pin closest the "back" of
the card, and on the top, if the pins are held down and the "back" of
the card is to your right:
----------------------------------------------------------------------
| |
| |
| |
| |
| |
| |
+---------------------------------+ +---+ +---+
| | | |
+----------+ +---------------+
A A
3 1
1
The "B1..B31" pins are on the reverse side of the card.
- Ted