Timing issue when GPS used with NB-IoT

RE: Timing issue when GPS used with NB-IoT

paul_tanner — Wed, 17 Mar 2021 09:29:07 GMT

I tried something else and it worked. Just before sending data I stopped GPS with gnss_ctrl()

after sending I waited for LTE idle before restarting. Error messages no longer seen.

Solution.

RE: Timing issue when GPS used with NB-IoT

paul_tanner — Tue, 02 Mar 2021 10:12:46 GMT

Thx. Will try that but in the mean time I read something else here:

https://devzone.nordicsemi.com/f/nordic-q-a/57448/nrf9160-gps-hangs-when-starting-after-stopping

Specifically, there is apparently a GPS driver in the SDK. The provided GPS example doesn't use it but would this not be a better approach than just polling for a fix?

RE: Timing issue when GPS used with NB-IoT

helsing — Thu, 25 Feb 2021 19:23:19 GMT

Sorry for the delay.

You may read about Continuous navigation mode here:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.0/nrfxlib/nrf_modem/doc/gnss_extension.html#fix-interval

'Continuous navigation mode is engaged by setting the fix interval to one.'

RE: Timing issue when GPS used with NB-IoT

paul_tanner — Thu, 18 Feb 2021 09:02:02 GMT

Thanks and sorry for slow reply as I was held up from doing any further field tests.

Not sure what you mean by GPS "continuous mode". I'm using the code from the GPS example.

Anyway, I removed any attempt to stop GPS. This is working much better now but I do get at least one "GPS deadline missed" per UDP transmission. This could be ignored but it might be better to pause GPS after a fix and wait until the UDP transmission is done. I'm not sure how best to do that.

RE: Timing issue when GPS used with NB-IoT

helsing — Thu, 04 Feb 2021 10:58:59 GMT

Could you please specify how you experience the result as being unstable?

In which mode is the GPS? Is it in continuous mode? LTE has priority over GPS so you do not need to turn off GPS in order to send over LTE.

However, you might need to make sure all data sent over the GPS socket is read. If the buffer shared between the application and modem is full you will not be able to send anything back and forth.

RE: Timing issue when GPS used with NB-IoT

helsing — Fri, 29 Jan 2021 14:17:15 GMT

Hi Paul,

I will look into this and get back to you next week.

Best regards,

Håkon