Modem problems on D-Class with EISA MUX
Deron E. Meranda
I have been trying to set up external modems for dial-in access on
several D-Class servers using an EISA Mux card. The problem I am
experiencing is that the data communication will sometimes hang in one
direction--for instance I may see the /etc/issue and login prompt, but I
can not type anything in.
The servers range from a D200 to a D350/2, all using the J2482A 8-port
EISA Mux card. The modems I have been using are Pratical Peripheral
(http://www.practinet.com/) external 28.8 and 33.6 kbps. I am running
HP-UX 10.20 with all the patches up to the May 1997 Extension Software
set. I have installed the EISA MUX software J2467B_APZ off of the
Applications CD.
I am trying to set up the modems to use hardware (RTS/CTS) flow control
and have already refered to the "HP EISA Multiplexer Familiy Cabling,
Diagnostics and Troubleshooting Manual" as well as searching the HP
online knowledge base. I have used several different mux ports, modems,
cables, and even servers - so I doubt it's any one specific hardware
fault. My cables send all ten signals (TD, RD, RTS, CTS, DSR, DTR, GND,
CD, and RI), and match the pinouts from Figure 4-8 in the cabling
guide. I have attached RS-232 monitors and all appears fine. I have
even disconnected the modem and forced various DCE lines high and seen
them respond with the emux_stty(1) command and within the emux_diag(1)
"breakout box" display.
Unfortunately SAM is not capable of creating modem devices which use
hardware flow control, but I am fluent enough with mknod and insf to
make the devices myself. For instance, on port A2 I have the following
device (emux card instance 2):
/dev/ttyd2a2_rts crw--w--w- root:tty 75 0x020112
which is easily verified,
# lssf /dev/ttyd2a2_rts
eisa_mux0 card instance 2 port a2 callin HW flow control at address
20/5/2 /dev/ttyd2a2_rts
I can connect to the modem using cu(1) at 115200 baud. The modem is set
to factory settings with auto-answer enabled. BTW, this defaults to
RTS/CTS hardware flow control.
I am using /usr/sbin/getty and supply it with the correct device and
speed with the following command in the /etc/inittab:
/usr/sbin/getty -t 60 -h ttyd2a2_rts 115200
I have also tried an alternate gettydef entry (which I called H115200)
which is just like the default 115200, except that I replaced CS7 with
CS8 and removed PARENB, IXON, and ISTRIP to make it more appropriate for
8-bit hardware flow controlled lines. But from the discussion in the
emux_stty(1) man page, I belive the mux hardware/driver overrides any
software termio settings anyway.
Sometimes this setup works wonderfully, and I have achieved data
throughput up to about 10 KB per second without any data corruption or
loss! However, occasionally a port will exhibit this hanging behavior,
usually right at the beginning of the login process. Resetting or
repowering the modems does not help. And once hung, that same port
seems to continue that behavior on every new dialup connection as long
as the system remains up. However, I can continue to use cu(1) just
fine and talk to the modem in AT-command mode (but keep in mind most
modems ignore RTS/CTS while in command mode).
Also, when this condition occurs, most of the time I will see the
/etc/issue file and the login prompt displayed (at which point all
communication ceases), but I have also seen the case where no data
whatsoever is sent or received after the connection is established.
This really seems to be some kind of flow control problem, but I'm
really stumped trying to figure it out. It's not the local modem
because I've tried many different kinds on many different systems; all
of which work just fine connecting to non-HP servers.
As an interesting side behavior, when a port becomes "hung", I'll stop
the getty process (set it to "off" in the /etc/inittab followed by init
q). Then when I try to use the command:
# emux_stty -m </dev/ttyd2a2_rts
it hangs indefinitely. But after I connect to the modem using cu(1) and
issue an AT, then the emux_stty command works afterwards. But the modem
will still hang the next time I try to long in using getty.
This problem is really frustrating. Can anybody help? Is it a modem
problem, configuration problem, HP hardware, or what? Has anybody ever
successfuly used hardware flow control with a modem on an HP EISA MUX?
Thanks for any suggestions...
--
Deron E. Meranda <dmer...@medplus.com>
Sr. Technical Staff -- MedPlus, Inc.
John Pezzano
"Deron E. Meranda" <dmer...@iac.net> wrote:
:I have been trying to set up external modems for dial-in access on
: # emux_stty -m </dev/ttyd2a2_rts
It sounds like everything is configured right. My first question would
be "Do you have patches"? There are known problems with the EISA mux
fixed by patches.
I also filed SRs regarding the inability of some of the modem
communication programs to properly create lock files in the correct
directory and when device file names are longer than 9 characters (14
characters including the /dev/). I notice you are using longer names.
I don't know if those problems have been corrected.
In any case, if you are not up on patches, I would suggest this be
your first step.
--
jo...@atl.hp.com
HP TIS
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