Difference between GPS_EVT_PVT_FIX and GPS_EVT_NMEA_FIX

[XavierN]

I am looking at the nrf 1.3.2 asset tracker example and I see that the GPS callback has two different events for PVT and NMEA fixes. As I understand it PVT and NMEA are two different ways of expressing the fix data? Why are there two different events for those and under what conditions are they triggered?

Thank you.

Xavier

[Håkon Alseth]

Hi,

 

As I understand it PVT and NMEA are two different ways of expressing the fix data?

PVT stands for position, velocity, and time. NMEA is a defined ascii representation of the gps data. If you search for "nmea explained" you should see more detailed information related to this format.

In nrf_socket.h, the pvt struct is a binary representation of the information found in the nmea strings:

https://github.com/nrfconnect/sdk-nrfxlib/blob/v1.4.0/bsdlib/include/nrf_socket.h#L777-L792

 

Why are there two different events for those and under what conditions are they triggered?

For NMEA, you can select the frames you're interested in, as shown here (where all are enabled):

https://github.com/nrfconnect/sdk-nrf/blob/v1.4.0/samples/nrf9160/gps/src/main.c#L140-L144

For pvt, its given as a struct.

The reasons they're split in the driver is because they're also split in the API from the modem (bsdlib) side:

https://github.com/nrfconnect/sdk-nrf/blob/v1.4.0/samples/nrf9160/gps/src/main.c#L305

https://github.com/nrfconnect/sdk-nrf/blob/v1.4.0/samples/nrf9160/gps/src/main.c#L321

Kind regards,

Håkon  

[XavierN]

Thank you for the quick answer!