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Re: How to avoid 1Hz batching of 10Hz GPS fixes?


From: Chris Dew
Subject: Re: How to avoid 1Hz batching of 10Hz GPS fixes?
Date: Mon, 21 Oct 2024 15:40:43 +0100
User-agent: Mozilla Thunderbird

Hi Gary,

Thanks for your help; as you suggested, it was a baud rate issue.


The fix was:

/etc/default/gpsd:

# Set ublox MAX10S to 115200 baud
export UBXOPTS="-P 34.10"
/usr/bin/ubxtool -f /dev/ttymxc1 -s 9600 -S 115200 && yes  # This is only ever needed/successful once.
GPSD_OPTIONS="-n -s 115200"

/etc/rc.local:

# Get GPS fixes at 10Hz.  Even though gpsd starts before rc.local, a delay is needed for it to work.
( sleep 15 ; /usr/bin/gpsctl -c 0.1 ) &



All the best, Chris.



On 18/10/2024 23:19, Gary E. Miller wrote:
Yo Chris!

On Fri, 18 Oct 2024 11:48:31 +0100
Chris Dew <chris.dew@thorcom.co.uk> wrote:

But, before you do any of that, update to gpsd 3.25 or better yet
git head.  
Now using HEAD:
Good.

     serial or USB connection,  
serial  
What speed?  
9600
That is WAY too slow for 10Hz.  The output of "ubxtool -t -p STATUS"
will likely show your output buffers are 100% full.  No pause bewteen
packets because there is not enough speed to get the all out, and have
a pause.


Or "ubxtool -t".  Try ubstool both with, and without gpsd running.  
Using ubxtool -t when gpsd is running shows *8* and _9_ batched 
UBX-NAV_PVT messages per second.
Yeah, classic buffer overflow.  The GPS is filling the serial link
and still needs to drop messages to keep up.

Notice that the (bold/underlined) arrival times are batched, but that 
the "nano" times are correctly 100ms apart.
Sorry, I dont udnerstand what you mean.  And you output corrupted
with asterisks...

without gpsd running.  
Using ubxtool -t when gpsd is stopped:

root@999AAAAA:~/gpsd# ./gpsd-3.25.1~dev/clients/ubxtool -t
ubxtool: failed to connect to gpsd [Errno 111] Connection refused
Sotty, I figured you would know to add the "if /dev/ttyaxc1" parameter

Can I make ubxtool connect directly to /dev/ttymxc1, without gpsd?
Yes, that is what I asked for.  You just need the "-f" parameter.

I tried:

root@999AAAAA:~/gpsd# ./gpsd-3.25.1~dev/clients/ubxtool 
--device=/dev/ttymxc1
ubxtool: failed to connect to gpsd [Errno 111] Connection refused
"-f XX" not "--device".  Spend some time with the man page and
the unxtool examples.

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

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin


--

Chris Dew / Senior Developer
Email: chris.dew@thorcom.co.uk

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