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Re: [gpsd-users] gpsd loses the connection with the M8T when Raw is enab

From: Gary E. Miller
Subject: Re: [gpsd-users] gpsd loses the connection with the M8T when Raw is enabled.
Date: Sat, 13 Apr 2019 16:29:17 -0700

Yo Stéphane!

On Sat, 13 Apr 2019 15:16:48 +0200
Stéphane Péneau <address@hidden> wrote:

> I use a Raspberry Pi 2, with Raspbian Stretch (4.14.98) and a U-blox 
> neo-M8T connected on the uart and the timepulse on the gpio18.

Cool, I have similar here.  Except my M9T seems dead right now...

> I need the nmea stream for a python script, and the raw stream to 
> postprocess the data with RTKLIB.


> When only nmea is enabled, everything is fine.


> But when I enabled UBX-RAWX and UBX-SFRBX, gpsd regularly loses the 
> connection and I don't receive any data for a few minutes.

UBX-RAWX and UBX-SFRBX is a lot of data.

Looks like your speed is 115,200, which may be a tad slow, or not:

    gpsd:INFO: SER: speed 115200, 8N1

You have a LOT of checksum errors:

gpsd:IO: UBX checksum 0x6ef7 over length 61, expecting 0x0c25 (type 0x6201)

That points to a serial port problem.

I would put an oscilloscope on it and check the voltage levels of
the serial lines, the voltage on the M8T, and that the serial line is
not saturated.

Also try a faster speed.

You neglected to say how you started gpsd.  Be sure to use the -n option.

> When I start gpsd with debug enabled, I see that it retry to connect
> to the uart with a different speed and I don't understand why.

Autobaud.  To stop autobaud, just set the port speed correctly before
starting gpsd.  Or just let it do its job.  Which seems like it
is working for you.

> The full  log is attached with this mail

Here is the interesting part:

    gpsd:INFO: launching (Version 3.18.1)

Please try git head.  There has been a lot of work for u-blox 8 and 9
since then.  But I see nothing in your logs that git head might
affect.  YMMV.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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

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