GPS fix times and possible memory leak

[Tron]

We have a custom board with nrf9160, ncs 1.2.0 and modem fw 1.1.1. We experience strange behaviour with the GPS: As an example,on units with 30 min fix intervals, we experience the following with units in the field: 

1. In the beginning, the unit has fix times of roughly 2-5 secs, with the occational 30 sec fix time
2. When the unit runs and have sent roughly 500 messages, the fix times are increasing, and often passes 1 min
3. After roughly 1500 messges, we see that the GPS takes a fix every second try, and when it takes a fix, the fix times are longer than a minute.
4. When the user resets the unit, we are back to point (square) 1. 

For us, this looks like a memory leak in the GPS modem fw. 

Yours, 

Tron

[Øyvind]

HI Tron, 

I'm on the case and will need to discuss the matter with our R&D team. I will get back to you asap!

Kind regards,
Øyvind

[Tron]

Hi

Modem trace is unfortunately out of the question. The units are on sheep in rural areas of Norway. 

I log the GPS Fix times to the server, or to be more precise, every second second I increase a fix counter, which is transmitted to the server every time the unit tries a GPS fix. I have a timeout on the GPS on 2m30s, so every unsuccessful GPS try gives a value of 75, ie 150 seconds. THis is the only logging, together with the GPS positions, of course. 

Resets are also logged. 

Are these of interest?

[Øyvind]

Tron said:

Modem trace is unfortunately out of the question. The units are on sheep in rural areas of Norway. 

 As anticipated, but needed to ask.

Tron said:

Resets are also logged. 

Are these of interest?

 Yes, these can be of interest. Please attach logs for further investigation.

 How does the user reset the device? What kind of GPS antenna is used? Can this be an issue with GPS signals e.g. if sheep are in an area with bad GPS reception or similar?

[Tron]

Hi again

the user resets the device by catching the animal, taking the betttery out and putting it again while holding the animal. 

The gps antenna is an Antenova SR4G008, if my old eyes don't deceive me. 

The logs don't say anithing except that the unit was reset, and sending SIM card, modem and version data. The interesting part is the GPS fix times before and after the reset.These are presented in the web interface. I  

Yours

Tron 

[Øyvind]

Hi Tron, 

Thanks for the information!

Are you able to reproduce this in your lab? It would be very helpful to get a modem trace. On how many devices do you see this issue on? I will continue with the investigation here. 

Kind regards,
Øyvind

[Tron]

I will try it, I have a gps receiver in my lab, but this is probably not a good environment to test in. Right now I have a problem with the modem traces in another case. 

Yours,

Tron

[Øyvind]

Hi Tron, 

Yes, I saw. Please prioritize accordingly and respond to this case when able. 

Thanks!

-Øyvind

[Tron]

Hi Øyviind

We've sorted out the modem trace issue. The question is, do I need to start the debug trace when the device starts, or is it sufficient to start it when the problem occurs?

This is a question of disk space management and power management issues. I'm in the process of starting the trial now. 

Tron

[Øyvind]

Hi Tron,

Tron said:

do I need to start the debug trace when the device starts,

 Yes, this needs to start when the device starts. Make sure to follow this guide when enabling modem traces

Kind regards,
Øyvind