[Xastir-dev] strange chars in APRS packets, xastir failed to decode path !

[Curt, WE7U]

On Thu, 17 Feb 2005, Thomas Hoffmann wrote:

> I'm new on xastir and I hope I do well by posting to this list. If not please
> excuse.

For problems where you think Xastir has bugs, this is the
appropriate list.  You did well.

For problems where it is a user education issue or just general
Xastir discussions, the "Xastir" list is the appropriate place.


> I'm running xastir since 2 weeks on a SuSE 9.2 box. Unitl last sunday
> everything was well, but then from one day to the other xastir stopped to
> decode APRS packets tranmitted by our local digi (DB0LC).
>
> Investigation revealed that there are  some strange "<UI>" characters in the
> digi path which prevented xastir from decoding the digi path. A log of my TNC
> traffic is shown below.
>
> ---------------------------------------------------------------
>  0:TNC-> IK3XTM-12>APRS,IQ3VO,WIDE7* <UI>:!4529.59N/01057.58Ej035/005
> Op.Gianluca ARI/R.E. Member
> ------------------------------------------------------------
>
> I went to my M$ windows box to check whether uiview was still decoding these
> packets. For my suprise it did well on them.

Interesting.  UI-View must have special code in there for that.


> Meanwhile I got in contact with the sysop of DB0LC. He told me that nothing
> has changed on the digi side and he could not explain why these <UI>'s are
> there, but promised to follow up the issue.

It looks to me like a setting changed in your TNC, perhaps you had a
power glitch (unnoticed?) and the TNC reset.  The portion:

    "IK3XTM-12>APRS,IQ3VO,WIDE7* <UI>:"

Is your TNC's printable representation of the AX.25 header.  In this
case it is adding the " <UI>" portion to the end to tell you it is
an Unconnected Information frame.  All APRS packets are UI frames.
There's a setting in your TNC to turn off this indication, in which
case the header will look like:

    "IK3XTM-12>APRS,IQ3VO,WIDE7*:"

instead.  Get the manual out for your TNC and change that option to
off.


> My last chance was to fix the xastir code, what I finally did. I added the
> following lines of c-code at the very beginning  of the "valid_path"
> function.

I personally believe that the TNC should be set up into the correct
modes by the tnc-startup.sys sorts of files.  If the commands are
not in there in the file for your TNC, we need to fix that.  If
you're using the wrong startup file for your TNC, you need to switch
to the correct one.


> Please reply directly, I've not (yet) subscribed to the list.

That's considered to be poor practice.  The "Xastir-dev" list has
relatively low traffic, so you should definitely subscribe if you're
posting there.

The "Xastir" list has more traffic, but still not all that much.
Some people subscribe to lists for a short period to ask a question
and then unsubscribe, but this is usually just needed for
high-traffic lists.

Asking people to respond directly may or may not work for you as if
a thread gets going on the subject people will not have your address
in the headers for long, all replies go back to the list address.

Yet another way of doing this sort of thing is just to ask the
question, then to keep checking the list archives to see what
activity it generated.

Many lists won't even let you post unless you are subscribed.  I'm
surprised that this one allows it.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"