[time-nuts] GPSDO standard interface?

Thu Jun 26 15:22:05 EDT 2014

USB may be a common interface to a computer but practically useless to another microcontroller.

Everything can do serial but not everything can do USB master. In the worst case, use a Serial-USB adapter on your PC. There is no such thing as a Serial-USB master interface and never will there be one. USB is PC centric.

Didier KO4BB

On June 26, 2014 2:13:00 AM CDT, Chris Albertson <albertson.chris at gmail.com> wrote:
>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
>>
>>
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>
>
>
>-- 
>
>Chris Albertson
>Redondo Beach, California
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>time-nuts mailing list -- time-nuts at febo.com
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