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Re: [gpsd-users] RAWX on u-blox F9P

From: Luke Reid
Subject: Re: [gpsd-users] RAWX on u-blox F9P
Date: Thu, 11 Apr 2019 11:48:39 +1200

Hi Gary

You're right I missed a key bit of information - the GPS is pre-configured (i.e. settings stored in flash on the F9P) to output the RAWX and NMEA messages over the UART0 port. This was done using the u-center ublox software.

This is going into an arm based computer serialport at 3.3v. It supports > 230400 baud. Have appropriate resistors in there so current shouldn't be an issue. The F9P is powered from a bank of lithium batteries with a buck converter and some filtering circuitry.

If you have a close look at the f9p_cat_tty.raw there is actually NMEA mixed in there with the ubx binary messages, at least there are in the file I have here unless it got garbled in transport.


On Thu, Apr 11, 2019 at 10:48 AM Gary E. Miller <address@hidden> wrote:
Yo Luke!

On Thu, 11 Apr 2019 10:15:31 +1200
Luke Reid <address@hidden> wrote:

> Thanks for the quick response.

Somedays are better than others.

> I can rule out the serial port speed, it was 115200, but I increased
> to 230400 to check and same behaviour.

Which port are you using on the F9P?  Maybe it is voltage, or power,

> Attached (I hope they make it through the mailing list) are 30
> seconds from the serial port directly using cat /dev/ttyS3, and
> gpspipe -R

This file is all NMEA:


Did you forget to change to u-blox binary mode?

This one bad in a different way:


It just has UBX-RXM-RAWX and UBX-RXM-MEASX, also not good.  How
did you configure the F9P?  It does not have the required binary for
proper operation.

> I'm using the latest version in git (release 3.19-dev, rev
> 3.19-dev-2019-04-10T06:21:48.007651)


> The gpsd command line is (although while testing right now not using
> pps. -b is because I have rx only to this device)
> gpsd -n -b /dev/ttyS3 /dev/pps0

So you are using /dev/ttyS3?

Unless you figure out how to get that GPS configured you are SOL.

Using the -b will make this almost impossible, unless you can force
your GPS, by default, into sending the proper messages.

> Serial port is setup thus before gpsd starts (of course it changes
> after that):
> speed 230400 baud; line = 0;
> min = 1; time = 0;
> -brkint -icrnl -imaxbel
> -opost
> -isig -icanon -echo

Looks good, assuming your port goes that fast.  What about the voltages
and power?  It helps if you do not pick and choose which of my
quesstions to answer.

> I put a debug message at the top of the ubx_rxm_rawx function and it
> doesn't seem to get called.

Because, as your capture above shows, your GPS was in NMEA mode.

Better way is to start gpsd at a high bedub level to see what is going on:

        # gpsd -nbND 4 /dev/ttyS0 /dev/pps0

> When I use RTKLIB (the latest from Tim Everett, modified to work with
> F9P messages), the raw dump from the serial port decodes fine, so
> probably the serial port itself isn't playing up at a hardware level.

And ubxtool decoded the RAWX fine.  You just were not sending it to
from your GPS.

> I hope this is enough info to go on, and thanks for your time on this

Well, except for the questions you skipped answering.

Most important: what are the voltage requirements of your /dev/ttyS3?
What voltage is you F9P outputting on its serial ports?  How are you
powering your F9P?  How are you configuring your F9P?

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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