Re: [gpsd-users] GBS sentence being output by u-blox despite being explicitly disabled

[Eric S. Raymond]

Michael Procca <address@hidden>:
> In my start up script, I explicitly disable GBS sentences with the
> following:
> 
>     echo -ne '$PUBX,40,GBS,0,0,0,0,0,0*4D\r\n' | socat stdin
> open:/dev/ttyS3,b9600,raw
> 
> And later start gpsd as follows:
> 
>     /usr/sbin/gpsd /dev/ttyS3
> 
> but GBS sentences are still output by u-blox AMY 5 chip.
> 
> However, if I use the -b option:
> 
>     /usr/sbin/gpsd -b /dev/ttyS3
> 
> Then GBS sentences are never output.
> 
> According to u-blox support, GBS sentences are disabled by default and I
> have searched through the gpsd source code (gpsd-2.96) and cannot find a
> UBX,40 message enabling GBS nor a UBX-CFG-MSG. I've read on the FAQ of
> some devices going catatonic unless the -b option is used - though it
> might be a stretch for it to trigger enabling of GBS.
> 
> Has anybody else had this problem and know why the -b option solves it?

I haven't seen this problem, but the range of possible causes is narrow
enough that I have a good idea what's going on.  

The -b option disables (among other things) the stock UBX probe in drivers.c.
Your report implies pretty clearly that the probe resets the device to
a configuration that ships GBS.

This is a design choice - or possibly an outright bug - in the uBlox firmware.
It is unclear what, if anything, we can do about it.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>