nRF9160 > GPS > RSSI?

[Oleh]

Dear Team,

Is it or will it be possible to get an RSSI info like we used to in nRF5?

Best

Oleh

[Håkon Alseth]

Hi,

 

For the GNSS, there is a C/N0 (carrier to noise density, more details here) field:

https://github.com/NordicPlayground/nrfxlib/blob/master/bsdlib/include/nrf_socket.h#L511

 

For the LTE part, you can get the RSRP (ref. signal received power) through AT command AT+CESQ, where the last number is a reference from -140 dBm. If you get "40", it would indicate -140 + 40 = -100 dBm signal.

 

Kind regards,

Håkon 

[Oleh]

Hi Håkon,

nice to hearing from you again!

Thanks for the link to nrf_gnss_sv_t struct, it sounds promissing :)

A short confirmation question: will these data be available only with the fix? Or could be accessed even if no fix is (still) available?

... trying to get the RSSI while Position-Reposition the device... in-/out-door...

also, thanks for the AT+CESQ info.

Best regards

Oleh

[Oleh]

Hi Håkon,

just a short from the field test...

I get the NMEA sentences without fix, these are not fully filled:

dump_gnss_data_frames > NMEA data
NMEA strings:
$GPGGA,000000.00,,,,,0,,99.99,,M,0,,*37

$GPGGA,000618.00,,,,,0,02,99.99,,M,0,,*3A

$GPGLL,,,,,000618.00,V,A*4A

$GPGLL,,,,,000617.00,V,A*45

$GPGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99,1*2D

$GPGSV,1,1,2,6,,,28,7,,,22,1*5D

$GPGSV,1,1,2,6,,,26,7,,,20,1*51

here, for the cn0 especially GPGSV is interesting, as we get sat info.

then I got PositionVelocityTime data:

dump_gnss_data_frames > PVT data
SV:6 cn0:65281 Sig:1 eL:0 Az:0 Flags:0
SV:2 cn0:15873 Sig:3 eL:1 Az:0 Flags:0
SV:4 cn0:2561 Sig:9 eL:1 Az:0 Flags:0
SV:7 cn0:11521 Sig:3 eL:1 Az:0 Flags:0
- Tracking: 4 Using: 0 Unhealthy: 0

Still no fix.... then getting more info:

$GPGSV,2,1,5,6,54,241,29,2,35,302,30,4,68,257,29,7,43,168,29,1*5A

$GPGSV,2,2,5,5,05,298,27,1*57

(so 5 sats)

and finally fix:

dump_gnss_data_frames > PVT data
SV:6 cn0:10497 Sig:3 eL:13825 Az:-3840 Flags:0
SV:2 cn0:12801 Sig:3 eL:8961 Az:11776 Flags:1
SV:4 cn0:8961 Sig:9 eL:17409 Az:256 Flags:1
SV:7 cn0:10753 Sig:3 eL:11009 Az:-22528 Flags:0
SV:5 cn0:4353 Sig:3 eL:1281 Az:10752 Flags:1
- Tracking: 5 Using: 3 Unhealthy: 0

... so I find this "filling values" good, probably side-effect, but it gives some info even before fix.

Thanks and best 

Oleh

[Håkon Alseth]

Hi Oleh,

 

That is good that it worked out on your end, at my end the data was unusable when I tested this without any connection. I guess you'll have to take the validity of the data with a grain of salt.

 

Kind regards,

Håkon

[Oleh]

Hi Håkon,

yes, you're right... it would be good if Nordic would Keep this Feature :) 

Thanks and best regards,

Oleh

[Oleh]

Hi Håkon,

I know -- ticket is closed, but related tiny question:

in the struct nrf_gnss_sv_t what are the values and description of "signal" and "flags"?

Edit: in Signal, I have values: 1, 3, 9... what is the meaning of these?

[Håkon Alseth]

Flags are defined here: https://github.com/NordicPlayground/nrfxlib/blob/master/bsdlib/include/nrf_socket.h#L531

And signal here: https://github.com/NordicPlayground/nrfxlib/blob/master/bsdlib/include/nrf_socket.h#L515

 

It sounds like your signal values are incorrect/corrupted. The documentation for the gps is still on-going, so it might be that some "garbage values" are still being pushed through to the application. I'll report it back to the devs so that they're aware of it.

[Oleh]

Thank you! Looking fwd to get the docs :)