Re: [gpsd-dev] [RFC] Add support for Airmar PB200 Weather station

[Eric S. Raymond]

address@hidden <address@hidden>:
> The Airmar PB200 [1] is a weather station to be installed on boats.
> It has built-in GPS, accelerometer, compass, gyro, anemometer, pressure and 
> temperature sensor. It has 2 outputs, one for NMEA0183 and one for
> NMEA2000 (I've seen the recent addition for NMEA2000, I'm interesting
> to make some tests and hacking around). 
> 
> It provides quite a lot of information and use the following NMEA sentences:
>  - Usual GPS ones
>  - TIROT, HCHDG and HCHDT for heading related data
>  - WIMWD, WIMWV, WIVWR and WIVWT for wind related data
>  - WIMDA for other meteorological data
>  - WIXDR for detailed transducer measurements/calculations
> 
> This is a WIP, I thought it might be worse to start the review early.
> Things I didn't look at yet:
>  - Update other tools (xgps, gpspipe, ....)
>  - Update the testsuite(s)
>  - Update documentation
> 
> I naively added a wind data structure, but the WIMDA would require to
> add yet another one (and in my case the WIXDR will bring even more
> meteo data than the WIMDA). So maybe these two should be merged
> together. Though, I didn't do it because there are several ways to
> express the wind, both for the wind direction and for the wind speed
> can be viewed from different referential frames: the moving boat, the
> moving water or the fixed ground, and why not one of these days the
> moving air mass (for flying things obviously).
> 
> It is likely that I will come one day with yet another structure:
> engine. I would like to install my openwrt/gpsd based system on a
> boat, and it has two engines that speak NMEA200 only (I let you
> imagine how high I jumped off my chair when I saw the new NMEA200 code
> coming in... ;))

I've merged the first two patches, and these patches in general look
good - thorough, clean, and workmanlike.  I encourage you to continue.
But as you note, there are some missing pieces.  Adding a device log
to the regression-test suite is a requirement.  And yes, you do need
to update the documentation.

There's a larger piece missing.  You've written JSON dumping for the
daemon, but you also need to write the JSON parsing for the client
side. That has to be in places before trying to modify cgps and xgps 
to display the new data will make any sense.

I've just written a Hacking Guide section on how to add a sentence
to the supported set.  It's a serious amount of work, and my hat is
off to you for having deduced and done so many of the right things on
your own.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>