[aprssig] NMEA Sentence problems into SCS Tracker....from Garmin Etrex
Stephen H. Smith
wa8lmf2 at aol.com
Fri Nov 23 12:30:34 CST 2007
Jack Chomley wrote:
> Hi all,
> Yesterday, my trusty Magellan 315 died, it was used on my mobile HF
> setup, using a SCS DSP Tracker, which all worked fine. So....I hooked
> my Garmin MAP76S up and away it went.
> I decided to get a Garmin Etrex (basic model) for the job, as all I
> wanted was NMEA V3 @4800 baud, which is what my other GPS units were
> working OK with, into the tracker.
> I set the Etrex up and no comms, check the interface settings. all
> OK....same as the MAP76S, which works.
> Despite resetting everything, still no go :-(
> Next, fire up my RS232 terminal....yep NMEA data is coming out of the
> Etrex fine, so I log the data sentences, THEN do a "read" on the
> MAP76S and find differences?
> Etrex Sentences
> MAP76S Sentences
> Looking at the logged sentence types, there are differences? I just
> bought the Etrex new, so I would say the firmware is reasonably up to
> date, maybe I need to try and load an older version, IF that is at all
> My MAP76S is about 4 years or so old, and its firmware has never been
> I would have thought that the $GPRMC sentence would have been
> sufficient, for the tracker to work off.
> So....I look to the collective wisdom of the group for a solution ;-)
Could it be that your tracker is choking on the longer (more resolution)
lat/long strings in new GPS hardware? I recall some discussions
problems with some hardware being caused by newer longer NMEA strings
mentioned on this list a year or two ago. I think the early TH-D7s
suffered from this problem when the NMEA-0182 Ver 3 format lengthened
the lat/long strings.
Have you looked at the actual number of digits in the lat / long values
output by the two devices. Some GPS devices have menu options to
"dumb down" the values sent out the port to NMEA 2.0 lower-res strings
for the benefit of older programs that choke on the improved longer ones.
Stephen H. Smith wa8lmf (at) aol.com
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