Re: [gpsd-users] Is gpsd supposed to be filtering NMEA sentences it doesn't understand?

[Ed W]

On 04/02/2015 13:40, Eric S. Raymond wrote:
> Ed W <address@hidden>:
> > I'm using GPSD 3.10.  I'm feeding it data from an airmar 200WX combined
> > wind/temp/pressure/everything sensor.  The raw serial port output includes
> > such sentences as:
> >
> > $YXXDR,A,9.3,D,PTCH,A,-7.5,D,ROLL*78
> > $YXXDR,C,,C,WCHR,C,,C,WCHT,C,,C,HINX,P,1.0180,B,STNP*43
> >
> > However, these don't emerge from gpsd (using gpspipe -[rR])
> >
> > - Is this deliberate?
> The packet getter discards these packets because the prefix YX is not in the
> list of known NMEA talker IDs:

I'm not sure where your referenced list comes from?  The gpsd web page 
lists "$YX" as being the talker id for "transducer"
    http://www.catb.org/gpsd/NMEA.html#_talker_ids

Assuming your list is from the source itself, would it be sensible to 
sync the source with the list of known talker ids on the web page?



> 2. GPSD's job is not to reveal NMEA quirks, it's to hide them.  Those sentences
> are a case in point; obviously XDR ought to be translated to a JSON ATT report.

Actually, be careful.  The XDR seems to be a general purpose way to 
provide transducer data and appears to be the direction NMEA are 
suggesting vendors should implement certain sensor readings.  eg I note 
several older sentences deprecated and referred to using XDR messages

The XDR format is described on the gpsd web page 
(http://www.catb.org/gpsd/NMEA.html#_xdr_transducer_measurement), but 
real examples seem to use multiple quadruplets to describe various 
sensor readings. The standard doesn't appear to enforce any special 
relationship or ordering on the quadruplets.

See the referenced PDFs below to see that various sensor data is 
returned by the 200WX, more than just attitude, eg temp (but that 
instrument has quite comprehensive attitude sentences - if you want a 
really full test then those docs would show good examples of all the 
sentences likely in the field)

> The right question for you to be asking would be "Can we add YXXDR to the
> set of accepted and parsed sentences?"  Possibly.  Full documentation, please.

Yes please.  Actually, from what you answered already, it seems I should 
request "Can we please add $YX and optionally other missing talker ids 
from http://www.catb.org/gpsd/NMEA.html#_talker_ids to the list of valid 
talker ids in gpsd"?

Further documentation to show this isn't theoretical is the docs for the 
PB100 on the airmar website:
http://www.airmartechnology.com/uploads/installguide/PB100TechnicalManual_rev1.007.pdf
Also for interest I found a document for the (unreleased?) 300WX here:
ftp://gyre.umeoce.maine.edu/pub/cinar/docs/airmar_wx200/300WXUserTechnicalManual_0183.pdf
The later document is perhaps worth saving if you have an Airmar/Furuno 
instrument since it covers the extra data offered by the 150/200WX which 
I haven't found documented anywhere else?

At least extending the talker ids to cover the $YX seems reasonable. I 
will ask others to chime in on whether other talker ids are sensible to 
add also?

Thanks for your consideration

Ed W