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[davegee]

Hello,

I have two EM406A GPSs that are used in time sensitive applications.  The first was purchased in mid 2009 and the second was purchased only 8 weeks ago.  If I leave both GPSs off for say 10 days (longer than the charge of the GoldCap backup), at first fix the old GPS gives a time 1 second fast when compared to the newer GPS and a third reference device (Motorola M665C GPS).  After 10 minutes or so of operation the older GPS corrects itself by counting a second twice.

I would presume the default leap-second setting of the older GPS dates to before the last leap second insertion, and the default leap-second setting of the newer GPS dates to after the last leap-second insertion.  Meaning sometime between mid 2009 and mid 2011 the manufacturer amended the ... er... firmware or lookup table or what-ever it's called in the devices memory.

Can I upgrade the firmware (or whatever it's called) in the older GPS so it retains the correct leap-second setting, and if yes, how might this be done?

Thanks for your help

Regards
DaveGee

[GS_TECH01]

Just a couple of questions about this:

Can you provide the serial numbers of the 'older GPS' and the 'newer GPS'? Also, where did you purchase both of those modules?
Another thing, please get the firmware version for both. To do this, you can refer to this forum posting: http://www.usglobalsat.com/forum/index.php?topic=3514.msg8979#msg8979
Can you also provide the specs/datasheet for Motorola M665C GPS?
Moreover, can you include some logs/screenshots about this 'leap-second' issues?

The more details you provide, the better for us to understand the problem. Thanks.

[davegee]

Hello Tech10,
Thanks for your reply.

The 'older' GPS is serial #10803, purchased in July 2009 from Sparkfun
The 'newer' GPS is serial #17745, purchased in July 2011 from Teledynamics

I have obtained the firmware numbers for both GPSs, which can be seen in this image...http://users.tpg.com.au/users/daveg/stuff/EM-406a_Firmware.png

I do not have a datasheet for the Motorola M665C, but the software that uses it's serial NMEA and 1PPS has a high reputation giving the correct time, as observed and reviewed by many observers in the astronomical community, where precision timestamping is paramount.

I have made a video of the time display of the various devices.  This image shows the display over 3 seconds.  I have labelled everything and I hope it is clear and understandable.

In summary;
-the device with the older EM406a was left for 24 hours to ensure the Goldcap was flat.
-all devices were started and fixes were obtained all devices were reporting 6 satellites or better
-the device with the newer EM-406a and the device with the Motorola GPS are giving the correct time
-however the device with the older EM-406a is running 1 second fast
-after about 12 minutes, the older device correct's the time by counting the 40th second twice.  This is detected by the device and it raises an error "Almanac updated.... "
-thereafter all 3 devices give the correct time.

I can also make available a brief 12 second video if need be.

Regards
DaveGee

[GS_TECH01]

Just checked with our engineers about this. Awaiting for their response.

[redapplejoe]

My experience with the EM406A is similar to that described by DaveGee.  My older unit is #12064 purchased in February 2011 from SparkFun.  My newer unit is #17576 purchased in July from Teledynamics. 

The newer unit has always indicated the correct time beginning with first fix, regardless of how long it has been without power.  The older unit displays correct time from first fix if it has been without power for 35 hours or less, and is one second fast after first fix if power has been absent for 36 hours or longer.

A series of 11 tests were performed over a span of 16 days to determine the memory retention time of the older unit.  Each test consisted of noting the time to first fix (always a minute or less), and noting whether the time derived from EM406A was correct or fast immediately after first fix.  Power was always supplied for 20 minutes, so presumably the backup capacitor was always charged to the same level, though perhaps less than the maximum.  WWVB was used to check visually on the time being displayed from the EM406A, and WWV was used to verify WWVB. 

In the tests for which the initial time was one second fast, a self-correction occurred (by repeating a second) 7 to 13 minutes after application of power.

These data lead me to believe that the firmware for my older unit was burned prior to December 31, 2008 (the occasion of the most recent UTC leap second), and the firmware for the newer unit was burned after that date.  If that is the case, is it possible to update the firmware for a particular unit?

redapplejoe

[GS_TECH01]

Hello davegee and redapplejoe,

Please check your emails for our response.

Let us know if you have any questions. Thanks.

[davegee]

Hello davegee and redapplejoe,

Please check your emails for our response.

Let us know if you have any questions. Thanks.

I'd just thought I'd report that I successfully uploaded the new firmware and the GPS reports the correct seconds after 122 hours in an unpowered state.

Thanks for your help.

Regards
DaveGault

[GS_TECH01]

Hello DaveGault,

Thanks for the update. And, good to hear that it's reporting properly now.

Let us know if you have any questions.

[redapplejoe]

Can you tell me when the leap second for July 1, 2012 will be incorporated in the firmware for the EM-406a?  Is it possible to specify that feature when making a purchase?

[GS_TECH01]

Are you referring to what firmware version? Can you please confirm?

[redapplejoe]

Hello, Tech10:
My product uses the EM-406a to provide precision time in a specialized application.  My present supply of EM-406a all have Firmware Version F-GPS-03-1006231.  When the leap second is added July 1, 2012, that firmware will be outdated, and any of those GPS that have not been powered for 2 days or more will display time that is in error by one second for about 15 minutes after first fix.  Our product alerts the user to this problem, but only after the 15 minutes have gone by.  That is acceptable, but not desirable. 

I anticipate buying additional EM-406a next month, and my preference is for those to include firmware that anticipates the July 1 leap second.  When will updated firmware be included in the EM-406a?

redapplejoe

[GS_TECH01]

What is this specialized application that you're referring to? Do you have any links, datasheet, or info about it?

Also, I have to check with our engineers about this. By the way, how many units are you planning to purchase for next month?

[redapplejoe]

Hello, TECH10 -

We use the 1pps from the EM-406a or MR-350P to derive time for stamping every frame in NTSC and PAL video with millisecond accuracy.  You can see a sample in a posting on this thread by DaveGee on Oct 17, 2011.

I anticipate buying 30 of the EM-406a and 10 of the MR-350P in early March, and really would like for them to have firmware that anticipates the July 1, 2012 leap second.

Thanks for following up on this.

redapplejoe

[GS_TECH01]

Based on our engineers, the current SiRF firmware version, GSW3.5.0_3.5.00.00-SDK-3EP2.01, does support leap-second. However, they would still confirm with SiRF to see if it does fix the leap-second issue. Please standby.

[redapplejoe]

Dear Tech10,

It is now nearly 2 weeks since your last post about the leap second problem, and it is only 18 weeks until the next leap second is inserted.  The string of 14 messages in this thread, beginning in October 2011, is an excellent summary of the problem, and perhaps you can call that to the attention of your engineers. 

I expect to make my next purchase of EM-406a in early March, and it is my preference that those have a new firmware version, to account for the leap second to be added this year.

Thank you for your assistance.

redapplejoe