[Xastir] My D700 says "EH?" almost every time it gets a "MYCALL" from xastir! Anyone else?

[Richard Polivka]

Tom,
  
  Sending a CR would flush the input buffer, methinks. I would proffer to  say that the buffer is getting garbage in it. The CR takes out the  trash.
  
  Now to find the source of the noise in the buffer.
  
  Good Luck!
  
  Richard, N6NKO
  

Tom Russo <russo at bogodyn.org> wrote:  I'm trying to diagnose and fix an extremely annoying behavior that I have 
always seen when connecting my laptop running xastir to the D700 in my 
vehicle.

I just made a commit to interface.c that fixed the problem I was seeing below,
but I don't much like what the solution was.  This mail is intended to
document the symptom and explain the fix.

Xastir sends "MYCALL xxxxx-xx" every time it is getting ready to transmit
a posit, followed by "UNPROTO...", then followed by the actual posit data.
Both "MYCALL" and "UNPROTO" are preceded by a control C (to get the TNC
back into command mode).   (ASIDE: The control-C before UNPROTO seems like it
might be unnecessary, since the first one should have gotten us into command
mode, but that's beside the point).

But almost every single time the "MYCALL" string is sent, my d700 replies
"EH?" instead of "MYCALL was xxxxx-xx".  This has been happening from the
very first day I ever connected my laptop to my D700 about 2 years ago.  The 
first time it happened the result was that the still-new TNC didn't know my 
callsign and SSID, and the posit went out with "NOCALL" as my callsign.  I 
fixed it then by manually connecting to the TNC with a terminal program and 
typing "MYCALL KM5VY-8" --- that stored my call sign permanently in the 
nonvolatile memory, and so ever since then these "EH?" instances have been 
unimportant, since until yesterday I only ever connected a single laptop to 
the thing with a single SSID.

It became significant again yesterday when I tried to connect a different
laptop with a different SSID --- the MYCALL line that xastir sends is, 
about 99 times out of a hundred, getting an "EH?" and the MYCALL value isn't 
getting reset, with the result that my KM5VY-5 laptop's posits were going out
with KM5VY-8's callsign/ssid in the packet.  Once in a while, though, it DOES 
work.  It appears to be random when it does, but it is extremely rare.

Since seeing this problem, I've tried now and then to figure out how to make
it go away.

I have toyed in vain with inter-character pacing values --- setting a very
long character pacing has NO effect on this behavior.

A few weeks ago I even tried changing the interface.c code to pause for
a second or more immediately after sending a control C to the TNC, on the
assumption that it was possible that the d700 pauses to think a while after
being told to go into command mode (there are other places where it is 
necessary to insert stupid delays so the D700 can work), but this also had no 
effect.  No amount of pause up to *5 seconds* after the first control C had 
any impact.  Scratch one theory.

And today I finally just tried something obvious: I hacked interface.c and
added a carriage return to the string sent to the TNC, right before the 
MYCALL.  This has, in quite a bit of testing, completely eliminated the 
"rejected MYCALL" instances.

Now the "EH?" is coming as a result of the leading carriage return instead.
That's why I don't much like the fix: it merely pushes the error message
from the TNC onto a meaningless, null command instead of the important MYCALL 
command.

Clearly, the D700 (or at least *MY* D700) has some Issues with the first
command given after being returned to command mode from CONVERSE mode with
a control-C.  I have no idea what those Issues are. 

I committed my changes to interface.c, because it seems a completely benign
thing to have an extra carriage return before the MYCALL for a regular TNC,
and it seems to be a necessary work-around for the D700.

So here's what I'm actually asking:

  - Do any other d700 users see "EH?" in their View Incoming Data windows
    right before "UNPROTO was ..." and a posit transmission by your station?
  - Does anyone have a workaround that I should know about?
  - Does anyone have a guess as to why such a huge fraction of these 
    MYCALL commands would be failing on a D700?
  - Anyone want to hazard a guess as to what might make it stop doing this?

This note also serves as warning to users of non-D700 TNCs to be on the lookout
just in case the leading carriage return I added to the MYCALL command is 
NOT as benign as I thought it should be.  Please let me know if you see any
strange behaviors resulting from this extra character in the outgoing command
stream.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick
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