[time-nuts] GPSDO standard interface?

Chris Albertson albertson.chris at gmail.com
Thu Jun 26 03:13:00 EDT 2014

If you want a common interface for GPS receivers it's "NMEA" and it's
relatively easy to implement.  I certain would NOT translate to TSIP as
that is rather obscure.  NMEA is a very common standard and many GPSes can
output NMEA.

Also you talked about "serial".  I hate to say it but "who in 2014 wants a
serial device?  USB is the only reasonable interface to a computer.  If you
used serial then you would just need to buy a serial to USB adapter so you
may as well build that into  your controller.   In 2014 those old DB9 and
DB25 connectors should be banned from all new designs.

Realistically the user interface in most home made gear is a few "#ifdef"
in the code at the top of the file.  You change those and recompile and
send the new software to the controller.  It's not bad having to re-compile
in order to support a different GPS receiver.  You would not want to swap
the brand of GPS in a user interface.  You do that with solder and wires
and recompiling

On Wed, Jun 25, 2014 at 8:14 PM, Bob Stewart <bob at evoria.net> wrote:

> After reading Chris's response, it dawned on me that I'm treading a
> different path from what I've seen on the list.  It's not so much a GPSDO
> as a general purpose GPSDO engine.  It uses a number of ideas from Bert's
> board, like the dual-rail op-amp output, but it also has a TIC, so it will
> have sawtooth correction.  I have included 2 TTY ports: one for the
> receiver and one for the PC interface.  I'm going to use the DAC on the
> dsPIC, but there will be an SPI port that can be used to drive an off-board
> DAC, instead.  There's also the possibility of switching some stuff around
> and having an I2C port, and the ICSP header could also hook up to an
> additional thermistor or two, or perform other digital functions.
> So, there will be some minor user fiddling, like with Bert's board, due to
> the flexibility of the OCXO.  But, I'll be using the P and D from the PID
> control system, so it shouldn't be difficult to setup.  There will be a
> power LED, an output enable LED, and a bi-color LED to signify status, but
> only the status would be necessary.  I'll do what I can to make it smart
> enough to plug and play for most circumstances, but I only have the one
> OCXO brand to test with at the moment.  I do have 3 receivers to test with
> now: Adafruit, UT+, and LEA-6T.  Keep in mind that I don't expect this to
> be a lucrative commercial business venture, so my budget is almost
> nonexistent.
> I'll look into both SCPI and TSIP, and therein lies the reason for my
> original post.  Essentially, have they been patented, and if so, have those
> patents expired?  Some companies guard their interfaces very rigorously to
> forestall competitive disruption.  I don't want to suddenly get a cease and
> desist letter or a notice of lawsuit over a hobbyist kit.  It's one thing
> to provide open source software to monitor/control a successful product.
> It's an entirely different thing to provide an alternative product with an
> identical user interface.
> I just ordered the first prototype boards today, but the software should
> be just a rewrite of what I did for the TIC on Bert's board, with a lot of
> extras thrown in.  Not that that doesn't mean a lot of work, of course.
> Bob
> ________________________________
>  From: Tom Van Baak <tvb at LeapSecond.com>
> To: Discussion of precise time and frequency measurement <
> time-nuts at febo.com>
> Sent: Wednesday, June 25, 2014 9:02 PM
> Subject: Re: [time-nuts] GPSDO standard interface?
> Bob,
> A couple of different ideas:
> 1) No UI at all. The surplus GPSDO favorites over the years (like the HP
> SmartClock's and Trimble Thunderbolt) work with no UI. Yes, there is a PC
> program you can use to monitor and control it, or even debug it, but it is
> completely optional. Many GPSDO work out of the box. Maybe, like HP, have
> one green LED to say all-is-well.
> 2) A very simple 9600 baud command set that you can use with any terminal
> program. Adding LCD is fine too. But make sure everything on the LCD is
> also available over RS232. Not everyone wants to visually monitor the LCD
> of every piece of gear on their bench; let a PC log and archive all the
> data, check for problems, make plots, etc.
> 3) Mimic enough of HP's SCPI command set so that GPScon and other tools
> like that can be used, transparently. I forget if your GPSDO includes a
> receiver or not.
> 4) Mimic enough of Trimble's TSIP so that LH and other tools like that can
> be used, transparently.
> Please write enough code so that the GPSDO, by default, can work "out of
> the box". I'm evaluating a prototype GPSDO right now that requires all
> sorts of user input just to get it started and to keep it going. That gets
> old. My bias is: time spent creating clever adaptive algorithms to make a
> human unnecessary is better than time spent creating an elaborate UI that
> requires a user (and operation manual) and constant monitoring or adjusting.
> /tvb
> ----- Original Message -----
> From: "Bob Stewart" <bob at evoria.net>
> To: "Discussion of precise time and frequency measurement" <
> time-nuts at febo.com>
> Sent: Wednesday, June 25, 2014 5:10 PM
> Subject: [time-nuts] GPSDO standard interface?
> In an offline communication, I suddenly realized that I hadn't given any
> thought to the user interface for my GPSDO. Is there an accepted standard
> interface for GPSDOs, or is that a murky Microsoft-esque world of patents
> and lawyers?
> Bob - AE6RV
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


Chris Albertson
Redondo Beach, California

More information about the time-nuts mailing list