[Xastir-Dev] Please try latest CVS code

[Curt Mills, WE7U]

On Thu, 17 Jul 2003, Stephen West-Fisher wrote:

> Something broke for HSP use there. I'm in the middle of a build at work
> and so haven't had a chance to look at the code, but a complete log
> follows. After the TNC is setup you decode no packets 'cause of the GPS
> strings.


> $GPGSA,A,1,,,,,,KQ4NO-5>APX121,WB4PBF-2*,WIDE:=2748.03N/08237.46W-PHG4100Steve from St. Petersburg, FL: steve at coastaldatasystems.com
                  ^HSP switch occurred between characters

> $GPGSA,A,1üKF4RTH>APR852,W4ACS-10,WIDE3-3,TRACE3-3:@172102z2749.6 N/08239.0 W_157/000g002t093r000p000....h00b   00dU2k
            ^HSP switch occurred mid-character

> $GPGSA,A,1¬WB4PBF-2>APW247,WIDE3-3:_07172049c132s005g007t097r000p000P000h99b10176wU2K
            ^HSP switch occurred mid-character

> $GPGSV,2,1,08,23,73,06ÿKE4UVQ-1>RW3Q1S,WB4PBF-2*,WIDE:'n?1l k/]"3m}D700A
                        ^HSP switch occurred mid-character

Interesting...  I expect to see some GPS strings thrown into the
normal decoding, which is the GPGSA/GPGSV strings in this case.  The
interesting part is that when you do the switch between GPS and TNC,
you get strings that are concatenated.

Probably we should thrown in a line separator into the incoming data
when we do the switch either way.  Blank lines are not a problem
'cuz the decoding logic will throw them out.  Concatenated lines are
a potential problem.  For the first part of them, the decoding logic
will try to decode them.  The last part will get thrown away, which
in this case is the important part.

I wonder if the code could be made even smarter:  At the point the
HSP switch occurs, wipe out the receive queue and any
non-printable-ASCII characters in the first byte or two.  If we did
that you would have perhaps decoded all four of the above lines
properly.  Seems like that might be worthwhile to try.

In any case, it looks to me like your GPS timing is too fast.
Correct me if I'm wrong, but it looks like you're not giving much
time for TNC strings to come in before you try to snag the next GPS
position.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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