nrf9160 modem XFILEWRITE gps almanac

[LordLucan]

Hi,

I see in the nrf9160 1.2.0 AT document there is a command XFILEWRITE that suggests the GPS almanac can be written and persist in the modem.

Can you provide more documentation on this command and the format of the data you can write?

I'd like to improve the TTFF for the GPS. I've got the SUPL GPS client example working and it does indeed speed up TTFF to a few seconds. But I'd like to be able to store that information in the modem in cases where I have no LTE connection or it is simply unavailable for other reasons. That is I want the GPS data to persist. Suggestions welcome!

Regards,

Paul

[Simonr]

Hi Paul

The GPS almanac/ephemeris data is stored into flash "by default". Flash storing of data happens regularly but rather infrequently (every 8 hours), but also on "graceful power-down". So the ephemeris and almanac data sit in RAM until either of the above happens. If the power-down is not graceful (e.g. battery is forcefully removed or upon a crash), the data will be lost.

Almanac is valid for months, so if it has at least once been stored in the not too distant past, it'll still be valid, even if there's a subsequent non-graceful power-down. Ephemerides are renewed every 2 hours regardless of whether it has been stored to flash or not.

If you need to store this data to flash more frequently, I guess you could call the XFILEWRITE AT command in order to do this manually upon, I.E. lost LTE connection or similar.

Best regards,

Simon