Re: [Paparazzi-devel] NMEA GPS Support in Paparazzi Code-base

[Martin Mueller]

Hi,

this NMEA discussion seems to pop up every once in a while. You can find 
them in the archives. The NMEA code that is in the repo is the 
(unfinished) result of one of these discussions.

NMEA is poorly specified and the resulting implementations are usually 
even worse. Look into NMEA parsing software packages (gpsd/gypsy) to get 
an idea of what GPS receiver developers can do wrong.

The more important point is that the GPS receiver type will play a big 
role in the autopilots performance. Not all of them are prepared to be 
used in an aircraft. The MT3329 GPS (there is an diydrones-binary 
protocol parser in Paparazzi) seems to be ok in normal flight but just 
repeats the old position data if the aircraft goes into tailspins.

Navilock sells complete u-blox receivers (even with a backup battery) 
for 30 Euros. Start with one of those, there is enough adventure ahead 
anyway :-)

Martin

On 01.02.2012 22:14, Roman Krashanitsa wrote:
> I agree with Felix
> NMEA sucks. Paparazzi uses fast, lightweight binary protocol that does
> not put additional strain on the autopilot processor (it needs that
> computational power). Also, ublox produces the best gps modules. Of
> course, they are not cheap.
>
> 2012/2/1 Jake Stewart <address@hidden <mailto:address@hidden>>
>
>     I agree NMEA sucks, but it seems that it is the standard.  Every GPS
>     I've seen uses it.
>
>     A NMEA parser should be a priority, and shouldn't be too hard to
>     implement.  NMEA seems pretty standardized, so most of the traffic
>     can be ignored I would think.
>
>     I'm still trying to learn the ins and outs of the PPZ design, but I
>     did finally get it installed.  The new windows Ubuntu installer
>     works pretty slick.  It sets you up with a dual boot setup and uses
>     a file on your NTFS drive for the linux filesystem, a virtual disk I
>     guess.  Anyways, it works with almost no user interaction or
>     knowledge.  The existing PPZ wiki install documentation works just
>     fine, but I'll update it with some more clear instructions.  The
>     whole thing does take quite awhile though.
>
>
>     -Jake
>
>
>      > ----- Original Message -----
>      > From: Felix Ruess
>      > Sent: 02/01/12 11:02 AM
>      > To: address@hidden <mailto:address@hidden>
>      > Subject: Re: [Paparazzi-devel] NMEA GPS Support in Paparazzi
>     Code-base
>      >
>      > Hi Jake,
>      >
>      > short answer: NMEA sucks (at least imho).
>      > Also the ublox GPS are quite nice and parsing a binary protocol is
>      > always more efficient than parsing NMEA strings...
>      > You can also configure the ublox GPS via the binary protocol at
>      > startup from the ap.
>      >
>      > Not sure what you mean by basic GPS interface. The interface is the
>      > same for all GPS drivers... ublox is just the most commonly used
>     one..
>      >
>      > That being said, of course it would be nice to have a properly tested
>      > and complete NMEA driver...
>      >
>      > Cheers, Felix
>      >
>      > On Wed, Feb 1, 2012 at 7:53 PM, Jake Stewart <address@hidden
>     <mailto:address@hidden>> wrote:
>      > > Chris, you might want to check out the Fastrax UP501 GPS
>     module.  It uses the same mediatek chipset and has better specs for
>     everything I checked.  It's also $28 (Mouser) instead of $60
>     (SparkFun).  I couldn't find any normal electronics distributors
>     carrying the LS20031, so that is maybe a red flag in some ways.
>      > >
>      > > I've got a UP501 and it seems to work well (limited testing
>     only).  I'll be working on getting that running also, so we could
>     share efforts.  I was really surprised to see that PPZ doesn't
>     normally support standard GPS.  Anyone know why an oddball protocol
>     was chosen as the basic GPS interface?
>      > >
>      > >
>      > > -Jake
>      > >
>      > >
>      > >> ----- Original Message -----
>      > >> From: Chris Wozny
>      > >> Sent: 02/01/12 08:44 AM
>      > >> To: address@hidden <mailto:address@hidden>
>      > >> Subject: [Paparazzi-devel] NMEA GPS Support in Paparazzi Code-base
>      > >>
>      > >> All,
>      > >>
>      > >> After having searched through the mailing list, it looks like some
>      > >> work was done on adding an NMEA parser to the guidance code. I was
>      > >> wondering the status of this since I emailed the original
>     inquirer and
>      > >> he told me that he never followed up on his attempt to try it. I'm
>      > >> looking to use the LS20031 GPS receiver (from Sparkfun) with the
>      > >> Lisa/M autopilot. It operates at 57600 bps with a TTL serial
>     interface
>      > >> just in case anyone is wondering. Has anyone used the NMEA
>     parser in
>      > >> flight yet?
>      > >>
>      > >> Best,
>      > >> Chris
>      > >>
>      > >> _______________________________________________
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>      > >
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