Re: GPS based on SIM68M chip

[Greg Troxel]

I have repointed this to the users list, following the guidelines in
SUPPORT.adoc.


Nick Taylor <nicktaylor@dataskill.uk> writes:

> I am working on a project using a custom TI 43xx armhf platform using
> the SIM68M GPS chip:
> https://www.simcom.com/product/SIM68M.html
>
> Wondering whether someone can confirm the support level of this chip
> within gpsd, from what I gather from Gary Miller, support for multi
> system receivers in gpsd is still being developed.

A few suggestions and comments

  While you see to have the recent release, it's best to build gpsd from
  sources from git for doing what you're doing (for now, until you're
  sure it's ok, and then you can go back to the release that is after
  all the fixes/improvements you make).

  Typically people implement support for what they care about.

  gpsd has worked well with more-than-GPS for a long time.  GPS and
  GLONASS has not been unusual for many years now.

  NMEA is in general messy, with lots of almost-conforming, variations,
  etc.

  Often people try to use the vendor binary protocol because it has
  richer data, fits over serial faster, allows more configuration, or
  some other reason.

  gpsd 3.22 decided this was a MTK-3301 with some kind of subtype.  You
  can certainly look up that and compare to the protocol specs from
  simcom, which says MTK but not which, and has two different version
  manuals, and get simcom to explain what's really going on.

  gpsd doesn't really care whose name is on the outer module, if the
  inner module is some particular ipmlementation.  I would advise
  getting a clear answer from simcom about what this really is.

  You are asking for someone to "confirm the support level" , and I
  really don't know what that means.  Free Software comes with no
  warranties.  If you want to know if it works, my advice is to test
  it.   The other thing to do is look at the source code.   A quick
  egrep -R for MTK shows some hits.

> $GNGGA,101338.000,5136.9361,N,00011.1058,W,1,9,0.96,87.5,M,47.0,M,,*67

That looks like a fix, and plotted on openstreetmap seems to be the park
across the road from a more likely office location

Nothing looks obviously messed up in NMEA, and I would look at xgps
output, check out gpsprof, and so on.

If you aren't already used to gpsd, I'd also suggest getting a ublox 8
in perhaps USB to plug into a regular computer (meaning ~POSIX, not
windows) and run gpsd with that.

The big thing you may want to look into is if there is some MTK binary
format.  That I have no idea about, not having any of their devices.

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