[time-nuts] Lady Heather for homebrew GPSDO

Bob Stewart bob at evoria.net
Sat Dec 17 21:21:45 EST 2016

I haven't had the time to look at the LH code yet, but is there a sort of natural interface that would most easily fit?  I'm speaking about both sides of the conversation: receiving data streams and sending commands.  It seems a bit strange to me that NMEA would be the preferred type of data stream.  And it should be obvious that giving direct access to the receiver would cause many problems.  

As far as emulating a Motorola: the Ublox is quite a bit different from the Motorola.  Synergy have spent quite a lot of time and money to produce their SSR-T boards that allow a Ublox receiver to look exactly like a Motorola.  I certainly wouldn't want to replicate that effort.



      From: Mark Sims <holrum at hotmail.com>
 To: "time-nuts at febo.com" <time-nuts at febo.com> 
 Sent: Saturday, December 17, 2016 7:28 PM
 Subject: [time-nuts] Lady Heather for homebrew GPSDO
If you are going to a GPSDO interface,  I would bite the bullet and recommend the Trimble TSIP / Thunderbolt commands.  It has its warts, but has commands for doing just about anything a GPSDO should do.  Doing a decent job would not be easy...  Nobody seems to have done a decent job emulating a Motorola receiver, and that is an easier thing to do.

The lazy bastard way would be cramming so proprietary NMEA sentences into a NMEA-like stream.

Polled interfaces like the Z3801A are horrible things for a computer to talk to.  If you miss a response or one gets garbled it can be difficult to recover from.  The Z801A is the worst possible interface... it's responses to requests have nothing in them to identify what request the values  are in response to.  

Heather really likes to see a device that sends regular time packets every second without having to request them.  Sending device status / TIC readings, temperature, etc is also a good thing.
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