USB-RS232 strange behaviour

[Rod Whitworth]

I have been using a USB-RS232 dongle for quite a while since DE9
connectors started going away on laptops.

Typically I use cu -l cuaU0 to connect and everything is fine.

Today I tried to use the same (dongle and command) on an old desktop to
talk to a Soekris 4801.

The message I got was /dev/cuaU0: Device not configured LF link
down

Strangely enough there was such device in /dev and I also found a stack
of cua00-cua03, cuac0-cuac7 as well as the cuaU0-cuaU3 I expected to
see.

Trying cu -l cua00 resulted in a response of Connected but there
was no boot message from the working 4801. It appears that there is no
traffic the other way either as I waited long enough for it to be fully
booted and then did a blind login.

An ssh session form another box was successfully made and I saw that
there was no console login.

Both the laptop and the desktop units are running the same OS - a 5.1
GENERIC beta dated around Feb 7.

Any educated guesses? Sure I can use the laptop but the desktop is in
my lab and should work. Obviously it sees the dongles, I tried both
with same result.

TIA,
Rod
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---
This life is not the real thing.
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Re: USB-RS232 strange behaviour

[Gregory Edigarov]

On Tue, 21 Feb 2012 22:25:50 +1100
Rod Whitworth glis...@witworx.com wrote:

 I have been using a USB-RS232 dongle for quite a while since DE9
 connectors started going away on laptops.

What chip is your dongle built on? 
When you connect it, do you see something in the logs/some changes in
dmesg?

 Any educated guesses? Sure I can use the laptop but the desktop is in
 my lab and should work. Obviously it sees the dongles, I tried both
 with same result.



-- 
With best regards,
Gregory Edigarov

Re: USB-RS232 strange behaviour

[Mihai Popescu]

Did you try to connect to that Soekris using your laptop? Maybe there
is nothing wrong with the dongle ...
A dmesg snip with that dongle detection would be interesting, too.
.

Re: USB-RS232 strange behaviour

[Paul de Weerd]

Hi Rod,

On Tue, Feb 21, 2012 at 10:25:50PM +1100, Rod Whitworth wrote:
| I have been using a USB-RS232 dongle for quite a while since DE9
| connectors started going away on laptops.
| 
| Typically I use cu -l cuaU0 to connect and everything is fine.
| 
| Today I tried to use the same (dongle and command) on an old desktop to
| talk to a Soekris 4801.
| 
| The message I got was /dev/cuaU0: Device not configured LF link
| down

Does USB work at all on that old desktop ?  My first guess would be
that it doesn't (perhaps it's switched off in the BIOS ?). 
Alternatively, the USB port you plugged into may be failing.

When you plug in the dongle, does dmesg show an attachment like the
following:

uplcom0 at uhub3 port 1 Prolific Technology Inc. USB-Serial Controller rev 
1.10/3.00 addr 3
ucom0 at uplcom0

(Note that this is for a dongle with a Prolific chip, your output may
vary)

The error you got is a clear indication that the dongle wasn't found
when you plugged it in, so either USB is not working on your machine
or that specific port you plugged into has issues.

| Strangely enough there was such device in /dev and I also found a stack
| of cua00-cua03, cuac0-cuac7 as well as the cuaU0-cuaU3 I expected to
| see.
| 
| Trying cu -l cua00 resulted in a response of Connected but there
| was no boot message from the working 4801. It appears that there is no
| traffic the other way either as I waited long enough for it to be fully
| booted and then did a blind login.

cua00 is for a true serial port, indeed more commonly found on older
desktop machines.  dmesg should show something like:

com0 at isa0 port 0x3f8/8 irq 4: ns16550a, 16 byte fifo

If the machine has a physical serial port, you could opt to use that
instead of the USB dongle.  It could also be just a header on the
motherboard of your machine (maybe not even that), so it's not a given
that there is a DB9 connector available to the outside world.

| An ssh session form another box was successfully made and I saw that
| there was no console login.
| 
| Both the laptop and the desktop units are running the same OS - a 5.1
| GENERIC beta dated around Feb 7.
| 
| Any educated guesses? Sure I can use the laptop but the desktop is in
| my lab and should work. Obviously it sees the dongles, I tried both
| with same result.

So, here you say it 'sees' the dongles; but it's not quite clear to me
what you mean.  If the desktop 'sees' the dongle (i.e. it attaches
correctly), the above statements are obviously not right ;)  Can you
post a dmesg please ?

Cheers,

Paul 'WEiRD' de Weerd

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