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GPS instead of NTP as accurate clock source

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George Bean
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I'm planning to use an XD1230 for emergency/disaster status information and during certain scenarios Internet access might not be available. I see a lot of posts regarding the use of a GPS connected to USB port 2 for determining location and geofencing. I also see a lot of posts regarding setting the internal clock using NTP with an Internet connection. I haven't found any mention of using the GPS NEMA 0183 data stream to set the internal clock to display accurate time. A received GPS time signal is as good as NTP and maybe better for any scenario I can envision involving Brightsign, if the GPS can be properly positioned to receive signals.. 

Since there is a designated GPS USB port, is there a provision in the firmware for setting the internal clock from a NEMA 0183 data stream?

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  • 0
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    Bright Scripters info[at]brightscripters.com

    Hi George,

     

    To my understanding, the player keeps its time for a long time after access to NTP is lost.

    Can you think of an emergency event that would last more than a day, and there would still be people at the site, who would be looking at the digital sign?

    With that said, synchronizing the clock from the NMEA information is an interesting idea, in the context of digital signage on buses or ferries.

    Typically a GPS device triggers serial events, and those could be intercepted in a BrightAuthor plugin, which would use the time information to set the player's clock.

  • 0
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    George Bean

    Yes, I can think of such an event. Our application will be in the amateur radio portion of our county Emergency Operations Center. Since none of the operators working the station are county employees, we aren't allowed to access the county network and through it the Internet. The only way we will have Internet access is by tethering to an operator's cellular phone or using a cellular access point brought in by an operator. We don't have the monetary resources to pay for a full time Internet connection to be used a few days per year. Since station operations are secondary to taking care of one's own self, loved ones and property, there is no guarantee the person with a cellular access point, me, or the person with a hefty monthly cellular data allotment will be in the station when it's operational. Furthermore. we don't even know if the nearby cell towers will be operational, one important reason for having us there!

    I'm not liking the idea of dragging myself and my cell phone into the EOC to tether up, at least weekly, to keep the XD1230 clock accurate. Even if I did that, an emergency situation can last for days, weeks or months, witness hurricanes Harvey and Katrina. A portion of our county lies within the 10 mile evacuation zone for a nuclear power plant, in the event of an activation for an incident there, its doubtful we will be going home anytime soon. If the evacuation zone pushes out to 20 miles we have to relocate the EOC and as much of our equipment as we have time and strength to grab to a backup site, the equipment bay of a firehouse...

    One of my biggest issues during our activations is the remote sites we man all have multiple clocks and none of them agree. I bought small battery operated clocks to be synced to the server before departing for the remote sites. If the EOC is activated and one of my operators starts logging reports from radio traffic, without fussing around, I want the time on my Brightsign displays to be synced with the time stamped RSS feed from my local web server, county 700MHz digital radio system and the banner on the bottom of the local tv station(s), all of them GPS corrected. It's not going to happen in the EOC if I can do anything about it!

    And yes, I could turn the server into an NTP server but I expect it to have more than its share of background tasks without acting as an NTP server. It's a 6+ year old Atom motherboard chosen because it can run directly off 12VDC.

    Regards,

    George

  • 0
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    George Bean

    As I drove into the county seat this afternoon, I realized that even if we had access to the Internet by the county network, that connection is tenuous during huricaines and other severre weather events. There are four routes out of town for vehicles and fiber cabling. Three of the fiber paths cross rivers & large creeks in a manor that all but guarantee they will be severed if rains cause water to overflow the banks. If I rely on NTP, I have a 25% chance of maintaining an Internet connection during a severe weather emergency and that doesn't take into account congestion from everyone trying to use one of four paths.

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    Bright Scripters info[at]brightscripters.com

    Dear George,

     

    Thank you for the vivid picture. What I had previously pictured was a digital sign at a corporate office, from which everyone would flee upon emergency situation.

    Lets get this done for you then.

    Could you provide information about the GPS unit that you are using?

    Which BrightSign model are you using?

  • 0
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    JRB Technical

    Although not ideal, but a possible idea to fall back on if it is not possible to do directly on the BrightSign players.

    Use a Raspberry Pi to get time from GPS, and sync it's own clock, then it can be the NTP server for the time for the BrightSign Players.

    I have tested the NTP serving portion of this for players on a VLAN situation that does not have access to outside Internet to make sure all the players on the VLAN have the same time.  The GPS portion should be fairly simple as well.

    The RasPi's don't take that much power, even less if you want to only run them for a short time every day to update any clock drift on the players.

  • 0
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    George Bean

    I'm eventually planning to build an Arduino based NTP server, most of the parts are on the way from China and the instructions are at:

    http://osengr.org/Projects/NTP-Server/NTP-Server.shtml 

    However, I don't know how long it will be before I have time to assemble it, especially since I'll be building an advanced version to provide a 10MHz reference signal for our radios. I need to get my Brightsign project ready for an exercise at the end of October and if it works out well, I'll be creating a similar version for remote site(s) where the only "network" connection will be a 9.6Kbps serial RF modem feed. That will present an interesting future challenge, extracting two RSS feeds from the amateur radio version of the X.25 protocol supplied by the serial connection..

    The GPS device I've chosen to drive both the XD1230 and the NTP server is a board level implementation of the ublox LEA6T device. It has USB, serial & SPI data outputs, NMEA0183 data format selection, dual reference output pulses selectable up to 10MHz and compensated accuracy of 15ns. The boards are produced for quad copter navigation with USB output/powering and available on ebay for <$30USD.

    http://www.ebay.com/itm/Ublox-LEA-6T-GPS-Module-Compass-for-APM2-6-APM2-8-Pixhawk-PX4-Flight-Controller-/252716390631?hash=item3ad71218e7:g:tOoAAOSwOyJX-G4Z 

    Accessing output pulses and an external antenna connection require opening the plastic case.

    The datasheet for the LEA-6 series is available at:

    https://www.u-blox.com/sites/default/files/products/documents/LEA-6_DataSheet_%28UBX-14044797%29.pdf 

    Drivers and other documentation are available at:

    https://www.u-blox.com/en/product-resources?f[0]=property_file_product_filter%3A2706

    From the point of view of the XD1230, or any other Brightsign device, the LEA-6T configured for NEMA0183 is no different than any other GPS device delivering NEMA0183 data via USB. One needs to parse the incoming datastream for the following:

    ZDA - Data and Time

      $GPZDA,hhmmss.ss,dd,mm,yyyy,xx,yy*CC
  $GPZDA,201530.00,04,07,2002,00,00*60

where:
	hhmmss    HrMinSec(UTC)
        dd,mm,yyy Day,Month,Year
        xx        local zone hours -13..13
        yy        local zone minutes 0..59
        *CC       checksum

    The above is from a NMEA0183 reference I find useful:

    http://www.gpsinformation.org/dale/nmea.htm

    Another good reference is:

    http://freenmea.net/docs 

    Thank you to Bright Scriptors and John for being willing to assist with my requirement. Hopefully, once a solution is found it will be useful to other Brightsign users.

    Regards,

    George

  • 0
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    George Bean

    I added a post addressing Bright Scriptors & John but it's "Pending Approval", probably because I included web page links. It make take another day to appear...

    Regards,

    George

  • 0
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    Gallo

    Hi !

    reviving this thread as i am looking for a solution to get date and time from a GPS module connected to the USB port of a HD1024.

    Any news or help on that ?

     

    thanks a lot

  • 0
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    Romeo

    http://brightsignnetwork.com/download/Romeo/Set_Time_Date_USB_GPS_UBLOX.zip 

    Hi,

    The above link is for an old presentation/Plugin but that should still work and allow you to set the time for a BrightSign player based on a GPS signal.

    Romeo

  • 0
    Avatar
    Gallo

    hi ! 

    thanks for the link !

    i am quite new to brightsign scripting / plugin though... any details on how to use it ?

    So far, i have

    - loaded the presentation included in the link

    - in the presentation i have set port 2 as GPS receiver under presentation propoerties -> interactive

    - i have added the .brs plugin named "Custom" in presentation properties -> autorun

    doesn't seem to work. Brightsign is still displaying the wrong date/time

    nothing relevant found in the log file : nothing related to the plugin like the "print" lines in the script.

     

    thanks

  • 0
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    Gallo

    hi,

     

    i have found that the plugin is probably set tu use uBlox GPS.

    I own a BU353S4.. i have tried to customize the plugin to my needs but of course i am not sure at all !!

     

    thanks

  • 0
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    Gallo

    hi,

    still stuck on this.

    anybody has a version working with BU353S4 GPS module ?

     

    thanks a lot

  • 0
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    Gallo

    Hi,

     

    I ended up using a Raspberry Pi as a NTP server with the GPS connected to it.

    I would be interested in the full brightsign solution with the GPS connected to it though, so if anyone has an idea that would be great.

     

    thanks

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