[time-nuts] The GPS 1995 problem and the Heol Design solution.

[Sean Gallagher]

Good afternoon everyone,

     So as most (all) of you are aware at this point what seems to be 
like all of the Trimble Ace III GPS receivers have looped around their 
entire lifespan and are setting the date back to 1995. This is affecting 
many people with the Datum/Symmetricom TymServe 2100 units. My company 
had two such units (we had purchased a second one when the +1 second UTC 
thing happened not realizing it was a firmware v3 and 4 problem) and 
also a slew of Datum 635/637 PCI cards which use the Trimble Ace III as 
well.

     After some scrounging around on the web I found that a company in 
France, Heol Design (http://www.heoldesign.com/), had created an Ace III 
clone. I contacted them for some information and a quote on what sounded 
the most promising. These were the N014 and N024 units which were quoted 
to me as 85 euro for the 014 and 90 euro for the 024. I also asked them 
if they thought their units would correct the date problem and they 
reached out to Trimble who apparently was not able (or willing?) to 
provide an answer. Olivier Descoubès with Heol Designs however was 
willing to work with me for testing purposes and sent me 2 of the N024 
units so that I could test and see if they would work as true drop in 
replacements. I have attached the data sheets that I received on the 
units as well for your viewing.  I'm not as technical as most of you so 
maybe you'll see something that I don't get that you can work with.

     The units came in yesterday after COB and so this morning was the 
moment of truth. Short answer to everything is they don't seem to work. 
I hooked it in to both of my 2100's first the older Datum branded one 
then the newer Symmetricom brand (although they look physically to be 
the exact same underlying board) really just to try and cover all my 
bases. I let the first one go for about an hour and the second for only 
half an hour since I was already thinking this was a bust. While it was 
hooked up though I telnetted in and went into the GPS menu. It gave me 
my Lat/Long position and the satellites command was able to show me that 
I had plenty of coverage, but it was unable to give me the time.

     After that I hooked it on to one of my 635PCI cards and got one of 
my backup servers going. I started up the Datum application and it did 
go into GPS mode which was at first promising. Typically with these 
cards if there is a problem between the GPS receiver and the Datum card 
then it will automatically come up in Time Code mode and won't even 
recognize the GPS. I let it run for about an hour while I ran to lunch 
and when I came back it had still not put out time.

     My guess is that these new receivers use the "Extended date" format 
or whatever it's called that adds more bits on (3? - sorry I can't 
remember specifics) to correct the rollover and changes it from 15 years 
to like 157 or something like that. And it seems like this older 
equipment that a lot of timing solutions use cannot handle this new 
output and thus can't decode it. Again I'm just a Junior in college so 
this is all just theory but it's what my gut feeling is.

     I've also attached pictures of these new units. They are the same 
size and have the 8 pin stack. There is additionally a 10 pin stack that 
I had to trim down to get it to fit. Also the antenna connector is an 
SMB, same as the Ace III, however it is on the other plane of the board. 
So if you were looking at putting it in a 635PCI card like me I had to 
use tin snips and cut out a notch on the front plate of it to make it fit.

     So it looks like I had to take a page from Mr. Andrew Cooper's book 
and have set up a rig like his using the two 2100's in unison. I have 
GPS going into the older one which I have reverted back to it's oldest 
firmware (2.84 I think) and thus avoided the 1 second problem. This 
older unit is putting out a 1PPS into the newer one set mode for 1PPS 
that is on V3.1 of firmware with the time and date manually being set 
through telnet. Trying to do it at the unit face is not feasible don't 
try it and I couldn't do this on the 2.84 firmware version for some 
reason it wouldn't recognize the commands. A colleague of mine seems to 
think for some reason that I might start getting drift again with this 
setup. He said that the 1PPS may not be enough to discipline the other 
2100 do you guys have any thoughts on that? It doesn't make a lot of 
sense to me as it's just a pulse

     I had kind of a crazy thought earlier based on a project that I had 
considered doing. I've seen on the internet that some people have taken 
a Raspberry Pi and made a timing solution out of it. At least one using 
what looked like the same type of Trimble III card.

http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
http://musingsfromthe8thfloor.com/2015/02/08/stratum-1-ntp-server-on-raspberry-pi/comment-page-1/
https://digitalnigel.com/wordpress/?p=1781

Does anyone think it would be possible to do this with these new 
receivers and get it to work? Even if it was only used to discipline 
some larger clock unit like the 2100? Or maybe even using the older 
receivers but making the RPi correct the rollover problem somehow? It 
looked like without me putting a lot of work into it I wouldn't be able 
to get it going because of having to learn the pin programming and 
electrical theory etc. And I unfortunately do not have the resources at 
work currently to follow this line of thinking.

**** I have just received an email from Olivier and they are aware of 
the TS2100 issue from a customer of theirs in France. That customer is 
shipping them the unit so that Heol can investigate it in action with a 
2100 and can maybe come up with a solution.****

-- 
Respectfully,


Sean Gallagher
Malware Analyst
571-340-3475

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