GNSS Restart After Single Shot

[kingston]

I am using the GNSS Sample in SDK 1.8.99 to test sleep/wake cycles.

The GNSS example is correctly operating in single shot mode by setting the interval to 0.  After getting a single fix, execution ceases and current draw drops.

I created a kernel timer based on https://devzone.nordicsemi.com/f/nordic-q-a/59164/internal-rtc-example with the objective of waking the 9160 from idle,  Within my timer function I stop and start the gnss based on the guidance from here, https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/nrf_modem/doc/gnss_interface.html#gnss-interface

I have these lines in my timer function,  

printk("Timer function execution\n");

if (nrf_modem_gnss_stop() != 0) {
LOG_ERR("Failed to stop GNSS in timed reset");
return -1;
}

if (nrf_modem_gnss_start() != 0) {
LOG_ERR("Failed to start GNSS in timed reset");
return -1;
}

However, the gnss is not restarting/reacquiring a fix even though the print statement from my timer is printed to the serial and no error messages are printed either.  I can tell gnss is off both from the current draw not increasing an no updated NMEA/fix info on the terminal. 

What other steps are required to restart the gnss?  Would I have a different result if I put the system to sleep directly with __WFI() vs using the built in sleep from the GNSS lib?

Thanks!

[Albrecht Markus Schellenberger]

Hello David,

What other steps are required to restart the gnss?  Would I have a different result if I put the system to sleep directly with __WFI() vs using the built in sleep from the GNSS lib?

I’m honestly not quite sure why you are not able to restart the GNSS, but I wonder if this could have something to do with stopping/starting the GNSS in a kernel timer expiry function.

Does it make any difference if you offload the calls of the GNSS functions to a system workqueue handler instead, as illustrated here?

Another alternative might be to just add the restart of the GNSS in the polling event for new available PVT data.

Regards,

Markus