HE910/DE910 GPS acquisition speeds.

4 thoughts on “HE910/DE910 GPS acquisition speeds.”

  1. Hello,

    We have previously developed a product using the DE910-DUAL module and are now looking to move to GSM with the same product. This product needs to be ultra low power so the module will be powered off when not in use. 

    With the DE910 we are able to get an autonomous cold start GPS lock generally under 30 seconds. After powering the module down for sometime and powering it back up it appears to be a hot start and would lock in under 10 seconds – which is very desireable for our application. This leads me to believe the DE910 stored almanac and ephemeris data in non volatile memory.

    Moving to the HE910-NAG we have noticed that we are unable to get an atonomous GPS lock and have to go SUPL MS-Assisted to provide first lock. This takes over 1 minute as we need to wait until camped on the network first. However, after first lock the GPS reciever auto powers off. We can then boot in autonomous mode and lock GPS in under 10 seconds.

    My questions are as follows:

    1. Does the HE910 not store almanac/ephemeris data in nonvol?
    2. Does the DE910 store almanac/ephemeris data in nonvol?
    3. Are there any reccomendations to decrease the TTFF with the HE910?
    4. Is there a better recommended GPS module that will help provide near instant GPS lock from a completely powered off state?

    Thanks,

    Brad

    1. For instance, this is the NMEA stream and has been very similar for the past 4 hours without a fix.

      $GPSNMUN: $GPGGA,,,,,,0,,,,M,,M,,*66

      $GPSNMUN: $GPGSV,3,1,10,04,49,075,25,12,21,293,00,14,45,022,23,15,17,265,00*78

      $GPSNMUN: $GPGSV,3,2,10,18,24,330,00,19,12,072,00,20,00,090,00,22,44,356,00*73

      $GPSNMUN: $GPGSV,3,3,10,24,53,284,00,28,47,167,00,,,,,,,,*7F

      Thanks,

      Brad

      1. I am having similar issues, can sit for a VERY long time without getting a lock.  Can I ask the order of commands you are sending?

        My symptoms are that it acquires satellites but then dumps them all (can see in NMEA messages), so never actually gets a lock.

        1. Hi,
          to better clarify the problem I need to know which HE910 fw version you are using.

          Anyway, here you can find a sequence to use A-GPS to speed-up time for forst fix:

          ‘Non secure port (7276)

           

          AT$GPSNVRAM=15,0

           

          AT$GPSNMUN=1,1,1,0,0,0,0

           

          AT+CGDCONT=1,”IP”,”Apn”  ‘here you have to set your APN

           

          AT$LCSSLP=1,”supl.google.com”,7276

           

          AT$LCSTER=1,”…imsi…”,0,0 ‘for non secure connection

           

          AT$LCSLUI=1  ‘1 if 3G and 0 if 2G registered

           

          AT$LICLS=1

           

          AT$GPSQOS=50,50,150,0

           

          AT$LCSLRMT=1

           

          AT$LCSLK=1,1 ‘link context 1 to A-GPS

           

          AT$GPSSLSR=1,1

           

          …wait for “$LILCS: 0” and then activate context

           

          AT#SGACT=1,1