Re: GPS based on SIM68M chip

[Gary E. Miller]

Yo Nick!

> On Fri, 5 Feb 2021 10:34:47 +0000
> Nick Taylor <nicktaylor@dataskill.uk> wrote:
> 
> > 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  
> 
> My condolences.  All their doc requires a login, which I do not have.

I got a SIMCom login and grabbed their doc.  Somewhat better than
the usual Chinglish.  So far looks like the MTK3333 repacked.

> > I'm attaching debug log from gpsd -D9 and output from gpspipe in
> > case that provides info about the standards used within the SIM68M  
> 
> Can't tell standards compliance from logs.  That requires doc.

MTK3333 messages (PMTK*) are certainly not "standard", but not uncommon
either.

> I can verify is it NOT working with your gpsd:

Sorry.  I have to retract that statement.  I failed to notice you were on
crazy level of debug (-D9).  LOG_IO, (-D6) is sufficient for most receiver
debugging.  Higner is for debugging programmer errors.

> gpsd:UNK: Packet type 1 accepted 85 =
> $GPGRS,100300.000,1,4.17,-2.23,2.08,9.39,-8.72,4.76,0.48,9.77,-4.48,-1.76,-4.09,*4F\x0d\x0a
> gpsd:UNK: Packet discard of 85, chars remaining is 14 = $GPGST
> 
> When gpsd has to discard input, that is bad.

I checked the code. "discard" is used as a synonym for "consumed",
it does not mean anything bad in this context..  The $GPGRS message
was decoded correctly.  But gpsd does not use the information in that
message.  $GPGRS gives the range residuals, which are fun to know, but I
have no idea how to use them.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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