Motorola Oncore UT+ wrong date?

Discussion in 'GPS Technical Discussion' started by madlabs, Aug 30, 2015.

  1. madlabs

    madlabs

    Joined:
    Aug 30, 2015
    Messages:
    2
    Likes Received:
    0
    Hi,

    I have a Motorola Oncore UT+ that I use to keep time on my Nixie clock and other projects. It has been in use for well over a decade with no problems.

    Yesterday however, I noticed that the time is exactly one hour off. I fired up the debugger and the unit thinks the date is 1/14/2000. Multiple hard restarts yield the same wrong date. The wrong date makes my DST routine set the UTC offset incorrectly. Or rather, correct for that date but since it isn't that date...

    Any ideas why it might do that?

    Thanks!

    Jonathan - KK6RPX
     
    madlabs, Aug 30, 2015
    #1
  2. madlabs

    Nuvi-Nebie Moderator

    Joined:
    Aug 16, 2015
    Messages:
    2,355
    Likes Received:
    201
    Location:
    UK
    Have you confirmed that the unit is actually getting a 'Satellite fix' and is not just running on the internal Real Time Clock?
     
    Nuvi-Nebie, Aug 30, 2015
    #2
  3. madlabs

    madlabs

    Joined:
    Aug 30, 2015
    Messages:
    2
    Likes Received:
    0
    Yes. I have hard restarted the unit several times and waited until the synch bit is set. At the moment I have a 2d, 3 sat. fix so the time should be correct. The minutes and seconds are right and the hours would be right but my DST routine is setting it back an hour due to the date error.

    Funny, this thing has run fine for over a decade. I can just re-program and manually set the correct UTC offset but I'd like to figger out what the heck.

    Thanks!

    Jonathan
     
    madlabs, Aug 30, 2015
    #3
  4. madlabs

    Nuvi-Nebie Moderator

    Joined:
    Aug 16, 2015
    Messages:
    2,355
    Likes Received:
    201
    Location:
    UK
    I suppose you could check all the other registers ( Lat. Long. etc. ) to see if the date is is the only one reporting falsely, and also monitor the date against the 'real' date over some days to see if there is a pattern to the error, but it seems to be a more than just a single bit error. I'm not sure how time is sent from the satellites, e.g. is it sent like Epoch time on Unix machines, where 1440953597 seconds = Sun, 30 Aug 2015 16:53:17 GMT and 0000000001 = Thu, 01 Jan 1970 00:00:01 GMT ?, if so then the date calculation would be done on the Motorola Oncore UT+
     
    Nuvi-Nebie, Aug 30, 2015
    #4
  5. madlabs

    Nuvi-Nebie Moderator

    Joined:
    Aug 16, 2015
    Messages:
    2,355
    Likes Received:
    201
    Location:
    UK
    It looks like GPS has a similar system to 'Unix Time' detailed above, it has a GPS Zero time starting at 00:00:00 UTC on January 6, 1980, from this time two counters were started, a seconds counter and a weeks counter (with the seconds counter resetting as the weeks counter is incremented), originally the Weeks counter was 10 bits, so that everything zeroed after 1024 weeks (about 20 years), this resulted in a second GPS Zero time at t 23:59:47 UTC on August 21, 1999, however the Weeks counter was increased to 13 bits producing a GPS zero time every 157 years. Any GPS receiver that only uses the 10 bit week count rather than the 13 bit week count, needs to be supplied with the approximate date to within 3,584 days (9.8 years). So the question is, will every 10 year old Motorola Oncore UT+ be having the same problem?

    https://en.wikipedia.org/wiki/GPS_enhancement#Timekeeping
     
    Nuvi-Nebie, Aug 31, 2015
    #5
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
There are no similar threads yet.
Loading...