Re: [gpsd-users] Set up for time sync and separate serial port use

[Gary E. Miller]

Yo Randall!

On Thu, 9 Mar 2017 18:04:18 +0000
"Pittman, Randall" <address@hidden> wrote:

> I have a python app that connects to my GPS Compass (Hemisphere
> Vector V103), sets it up to send certain messages, and then records
> the messages as they come in and parses them with the pynmea2
> library.

You might consider adding that functionality to gpsd.

> However, I'd also like to sync the system clock (CentOS 7)
> with the 1PPS signal from the GPS. Here is how I'm considering doing
> this, but I have no idea if it will work:

Have you read the gpsd howtos?  Like the time service howto?

> serial connection      38400 baud, GPZDA @ 20Hz, PASHR @ 20 Hz, GPGGA
> @ 20 Hz, GPROT @ 5 Hz from V103 with 1PPS
> __   on DCD line
>   \                                   ________
>   |                                  /
>   |==================================|  USB-to-serial adapter >>
>   |    \\                            \________ Used by Python app
> __/     \\
>          \\
>           \\
>            \\                          __
>             \\  Tap RX line,          /
>              \\ Split off DCD line    |
>               \=======================|  Serial port (ttyS0) >>
>                                       |    used by gpsd for time sync
>                                       \__
> 
> Will this work?

The problem is there is no way for gpsd to talk to the GPS.  gpsd
will configure the GPS as it needs to be.

> What NMEA messages does gpsd need to work for
> time-sync? GPZDA only? My setup is currently outputting GPZDA at 20Hz

The minimal set of NMEA messages required is not a single unique set.
There are many ways to get the minimum.  You will need the sats used
(maybe GPGSV and or GPGSA) and PVT data (maybe GPRMC).

> I guess an alternate approach could be to set up the message sending
> in my app and then is there any easy way to record all the message
> data with gpsd?

gpspipe -r

> Oregon State University Location

Stop by if you get to Bend.

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

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