JN3 – InstantFix

10 thoughts on “JN3 – InstantFix

  1. Hello,

    I’m currently using a JN3 module with a MCU unit and the GL865 in the same hardware, but there’s not a direct connection between the GPRS and GPS modules on the current hardware I’m working on.

    I would like to know the most efficient way to implement the InstantFix on my platform using CGEE Data (offline). I’m not sure if the JN3 supports internal storage of EE, if it doesn’t I would like to know how I can store the necessary EE into my MCU and when necessary send it to the JN3 so it can have a hot start.

    I went through some documents like: SIRFInstantFix application note, GL865-JN3/SL869 Interface Application Note, Telit Jupiter JN3 EVK User Manual r0, and so on. If you guys can guide my way to such implementation it will be perfect.

    Best Regards,

    Denis Dantas

    1. Hello Denis, 

      as far as I understood, you have a board where GL865 and JN3 module are both present, but not connected togheter as bundle solution.

      Could you please write me the serial number of your JN3? Do you know if it’s a flash variant or rom variant?

      If you want you can also take a picture of the module and sent it to me.

      Before proceed with any further suggestion I must be sure what variant of JN3 are you using and what fw version is inside.

      So please send the $PSRF125*21 to the JN3 and it should answer with $PSRF195 as ACK message, that contains the FW version.

      Thanks & Regards,


      1. Hello Matteo,

        Our product currently uses three varieties of the JN3:


        GSD4e_4.1.0-P1 12/20/2010 354 GSD4e

        Standard – FLASH 4800


        GSD4e_4.1.0-P1 12/20/2010 354 GSD4e

        FLASH 4800


        GSD4e_4.1.2-P9 F+ 03/21/2014 080

        FLASH 4800

        Serial number of the device I’m currently working on: 14475B6L00155.

        1. Dear Daniel,

          the serial number you reported 14475B6L00155 is referred to PN JN3 B3B6-LR and this is equipped with GSD4e_4.1.0 P1 that is an old firmwre version.

          Let me clarify on a few things. The JN3 has two types of Extended Ephemeris (EE) usage, one is CGEE and SGEE.

          CGEE is Client Generated Extended Ephemeris and SGEE is Server Generated Extended Ephemeris.

          The CGEE feature is enable by default on our JN3 Flash based, and the receiver creates predictions for satellites it sees locally, and these predictions are good for up to 3 days. SGEE feature is based on Exteneded ephemeris downloadable from our AGPS server that basically could be with an extension day of 1,3,7,14 days.

          Please take in mind the possibility to upgrade your unit to the latest firmware version GSD4e_4.1.2 P9.

          Basically after your receiver has been in tracking it’s able to generate itself the CGEE for the satellites that it’s using for the navigation.

          Kind Regards,


          1. Hello Matteo,

            I’ve made a few tests with two JN3 flash based modules, one was using the old firmware and the other was using the new firmware. I turned them on and started to store their log. Then I turned them off, waited around 3min, turned them on and started loggin again. Both times they took approximately 3min to start sending coordinates with a valid fix. We experienced already cold start timing around 10 min, or even more. I’m sending the logs attached.

            Is there anyway that we download the EE, store them in the microcontroller and then send them to the GPS? This approach would be the ideal for our board, since we don’t have a direct connection between the modem and GPS modules.

            Best Regards!

          2. Hello Devis,

            looking at your log file was captured when the JN3 had been turned it on. From these log I could not calculate the entire TTFF timing.

            However from the NMEA log I noticed that your RF performances is very poor (see attached screenshot) and many satellites are under the JN3 sensitivity, so this is basically the main reason why you are experiencing long TTFF.

            Due to this fact, I have to ask you confidential documentation like your schematic and antenna used, please write all these information to

            ts-emea@telit.com .

            I’ll give you support from that.

            Best Regards,


          3. Hello again Matteo,

            I haven’t sent you an email with my schematics because 1. we have reviewed it with Telit before making the prototype, and 2. I was testing on my workdesk. Today I went outside to provide the best scenario conditions, and I made two logs: the first was around 10 minutes after turning off the module when it had measured a valid location, and the second was 1.5h hour after the turning off the module when it previously had measured a valid location. The first test it took 25s for getting the location and the second test it took 40s for getting the first location – both first locations had errors smaller than 100m.

            The situation I face is the following: we have trucks that are tracked with our device, which is intalled in positions that may result in poor signal quality. During sleep mode the JN3 is turned on every 30 minutes and the MCU sends coordinates to our server when there’s first valid fix. Sometimes we’re getting these sleep coordinates with more than 1km error.

            I’d like to know if it’s possible to download the ephemeris from the Telit servir, and send them from the MCU to the JN3 module. I think the ephemeris download from the satelite is what takes longer for the JN3 to get a valid coordinate, therefore downloading them from Telit would probably give us better results.

          4. Dear Denis,

            just one little verification, the board used for the test was equipped with 4.1.2P9 firmware wasn’t it?

            The overall RF performances look fine with the outside tests. Therefore the problem is when the board is installed on the truck  the RF will be very poor + the metallic materials present on the truck create a multipath phenomenon, that in most cases is the main factor of position error, because the antenna receive the RF signal reflected by the metal.

            Both logs are taken outside in good sky condition but I don’t know what the RF look when the application is installed in the truck.

            Do you think could you be able to provide me that log? 5 minutes of log could be also helpful.

            Regarding the SGEE feature I have to provide you confidential material that I cannot share here in the forum so please write an email to



            Best Regards,

          5. Hello Matteo,

            I just emailed you asking for the SGEE feature documents. Regarding the tests within the truck, we will put that in stand by for now and focus effort on the topology of connecting the modem to the JN3, plus using SGEE to see how significant will be the gain.