Re: [gpsd-users] Ublox EVK-M8T

[Gary E. Miller]

Yo Denny!

On Mon, 18 Sep 2017 18:28:38 -0700
Denny Page <address@hidden> wrote:

> I can confirm that gpsd doesn’t work with the EVK-M8T. I’ve
> encountered several issues...

We have other people reporting success.

> The first issue is that the gpsd auto-baud detection doesn’t appear
> to work well with the unit. At 115200, gpsd will settle on 4800 if
> the unit is in binary mode. It’s unclear why. This means that gpsd
> without the -b option will work once, but fail the second time. For
> the time being, I’ve locked the unit at 9600.

Have you tried setting the port speed before starting gpsd?  That
simple workaround usually suffices.

> The second issue is that a standard serial cable does not work. The
> EVK has the time pulse tied to both pin 1(DCD) and to pin 7 (RTS). I
> don’t know why they’ve also tied it to RTS, but it wreaks havoc on
> the kernel’s PPS detector, with ppstest reporting more than a
> thousand events per second. A custom cable fixes this. I am currently
> using a cable with just pin 1(DCD), pin 2 (TXD), pin 3 (RXD), and pin
> 5 (GND).

Are you sure you do not have a voltage level problem instead?  Many
ublox output at 3.5V and most serial inputs can not handle that.

> The third problem is where things get interesting. While gpsmon run
> against the tty device happily reports a functioning PPS with both
> the NMEA or UBX protocols, gpsd itself does not. Gpsd is rejecting
> the PPS signal:

Uh, no.  lease reread the output.  gpsd is accepting the leading edge, and
rejeecting the trailing edge.  Just as it should.

> Sep 18 23:36:50 k9 gpsd[15453]: gpsd:PROG: KPPS:/dev/ttyS2 assert> 
> 1505777810.100060219, sequence: 8, clear   1505777810.000026753, sequence: 8 
> - using: assert

Accepted edge.

> Sep 18 23:36:50 k9 gpsd[15453]: gpsd:PROG: PPS:/dev/ttyS2 Assert rejected 1Hz 
> trailing edge

Rejected trailing edge.

A pulse has two edges.  PPS uses the eading one, and ignores the
trailing edge.


RGDS
GARY
---------------------------------------------------------------------------
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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