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  • Case ID: 319547
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GNSS/GPS TTFF with A-GNSS after upgrade from v2.4 to v2.5

tpg

Hi,

we have product which is close to the asset tracker v2 on the v2.4 which works fine. Now to upgrade to v2.5 we made the changes from agps to agnss. Everything works fine, but the unit is seeing nearly no satellites. With all logging on I can see that the A-GNSS data is moved into the modem/gps receiver. Return code is ok.

A-GPS data we get via MQTT, but we split almanac and ephemeris.

Looks like flashing v2.4 firmware, getting a GPS fix and the flashing the v2.5 firmware without powercycle so it looks like we still see some satellites and get a fix. After a powercycle we don't see satellites. So, I guess there is a problem with the A-GPS data, which is still cached after a reset, but not after a power cycle.

Are there other differences that are made here between 2.4 and 2.5? Any ideas how can I debug from here?

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  • 0

    Hello, 

    Are you seeing the same issue if using e.g. cellular GNSS sample? Are you using A-GNSS/GPS

    A-GPS data we get via MQTT, but we split almanac and ephemeris.

    I assume that you are not using our nRF Cloud A-GNSS library, could you please elaborate more on how your method works?

    Now to upgrade to v2.5 we made the changes from agps to agnss

    What changes have you done? 

    Kind regards,
    Øyvind

  • 0 in reply to Øyvind

    Partially we use the nrf Cloud A-GNSS library. The overall structure/code is close to the asset tracker v2 (with roots down to connect v2.3 and ported to v2.4).

    The flow is very similar:

    1. We get a LOCATION_MODULE_EVT_AGNSS_NEEDED event
    2. We encode a agnss request (or two one for almanac one for ephemeris if needed)
    3. We send it to an mqtt topic (AWS iot)
    4. The backend forward this to nRF Cloud rest API
    5. The result is published over mqtt to the device
    6. The agnss handler uses nrf_cloud_agnss_process (nRF Cloud A-GNSS library) to send the data to the modem.
      1. in case the almanac/ephemeris is splitted we call the function twice, once for each reply

    This works with perfectly with v2.4 and it seems to work with v2.5 going through all steps and nrf_cloud_agnss_process returns OK for almanac and ephemeris. Just that with v2.5 the modem has a hard time to find GPS satellites, as if there was no A-GNSS data.

    The changes to v2.5 here are only in changing the names of everything (datastructures, events, apis) from A-GPS to A-GNSS.

    So concrete point I found now is, that there is a new REST endpoint location/agnss and agps is marked deprecated. Is it required to upgrade the backend to use the new endpoint?

    And is there a description of the binary format for the A-GNSS data? Has this changed?

  • 0 in reply to tpg

    Thanks for clarifying? What modem FW version are you running on your device? Are you able to provide modem traces from both 2.4 and 2.5 for us to compare? Do you have any logs that you can share? 

    Kind regards,
    Øyvind

  • 0 in reply to Øyvind

    The modem is on firmware 1.3.5, I currently don't have traces or a log, I can see about creating new logs.

    The A-GNSS data is requested and was received, nrf_cloud_agnss_process happly processes this data, the last time I created a log.

    What about my last questions in the previous post does the v2.5 sdk work with data from the agps, instead of the agnss, REST endpoint? What is the binary format of the agps/agnss data here, where is this documented?

    Best regards

  • 0 in reply to tpg

    I reached out to our developers.

    Make sure LTE is not blocking GNSS by checking that NRF_MODEM_GNSS_PVT_FLAG_NOT_ENOUGH_WINDOW_TIME and NRF_MODEM_GNSS_PVT_FLAG_DEADLINE_MISSED flags are not set in PVT notification when GNSS is running (https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/nrf_modem/doc/api.html#pvt-notification-flags-bitmask-values)

    tpg said:
    I currently don't have traces or a log, I can see about creating new logs.

    Yes, that would be helpful as it would provide more insight to the root cause. Modem traces would be preferred with the application logs, as this gives more information on what is going on inside the modem.

    tpg said:
    What is the binary format of the agps/agnss data here, where is this documented?

    The binary assistance data format is described here: https://github.com/nrfconnect/sdk-nrf/blob/v2.5.0/subsys/net/lib/nrf_cloud/include/nrf_cloud_agnss_schema_v1.h

    The changes in v2.5.0 are cosmetic. The data schema and the used MQTT AppID have not been changed, so the cloud communication should be the same as with v2.4.0.

    Make sure LTE is not blocking GNSS by checking that NRF_MODEM_GNSS_PVT_FLAG_NOT_ENOUGH_WINDOW_TIME and NRF_MODEM_GNSS_PVT_FLAG_DEADLINE_MISSED flags are not set in PVT notification when GNSS is running (https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/nrf_modem/doc/api.html#pvt-notification-flags-bitmask-values)

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