Pytrack can't get GPS signal

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1

Hi everyone,

I’m having some trouble getting the pycom pytrack to pickup any satellites. I have posted on the pycom forum but I haven’t had an response there as of yet. [Gpy with PyTrack can't get gps working | Pycom user forum](https://pycom forum)

I have other GPS modules here that are working fine so I am familiar with the communications process involved.

So things I have tried:

  • Updated gpy and pytrack firmware
  • Left unit outside in clear view of the sky for 12 hours
  • Tested with and without external antenna
  • Check the dump_nema method and messages are being displayed/processed
  • Tested some other versions of the gps library that have been forked/modified on github

When I read the raw data from the GPS I can see that it isn’t picking up any satellites at all.

$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGGA,004345.864,,,,,0,0,,,M,,M,,*44
$GPGSA,A,1,,,,,,,,,,,,,,,,1*03
$GPGSA,A,1,,,,,,,,,,,,,,,,2*00
$GPGSV,1,1,00,0*65
$GLGSV,1,1,00,1*78
$GPGLL,,,,,004345.864,V,N*76$GPRMC,004346.864,V,,,,,0.00,0.00,060180,,,N,V*37
$GPVTG,0.00,T,,M,0.00,N,0.00,K,N*32
$GPGSA,A,1,,,,,,,,,,,,,,,,1*03,M,,*47
$GPGSV,1,1,00,0*65,,,,,,,,2*00
$GLGSV,1,1,00,1*78
$GPGLL,,,,,004346.864,V,N*75

Could the shield be faulty? Any ideas?

Thanks

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2

Hey Patrick,

Welcome to the forum!

I haven’t done too much reading myself of the PyTrack but I’ll do some digging and get back to you!

Liam.

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3

That’s convincing evidence the GPS module is not recognising a signal. I can’t think why you would get those messages any other way. Maybe a solder blob shorting the input, or missing solder. Maybe a good look with a magnifier will show something up. Also a gentle push on each component around the antenna to see if a pad isn’t soldered, you may detect a bit of give. Or if purchased in Australia just send it back and ask for another.

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4

Hey Patrick,

How are you going with getting it up and running?

Have you had a chance to run through the PyTrack tutorial that Core made a while ago?

It sounds like you’ve done most of the hard lifting already and sounds like it could be faulty at this point.

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5

Hi Liam,

Thanks for your reply.

No unfortunately I haven’t had any luck getting it working, I reckon there is something faulty on the board relating to the antenna as I can’t pickup any satellites at all with internal or external antenna.

Patrick

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6

Hey Patrick,

No worries! If you purchased it through Core it might be worth shooting them an email with the link to the forum to get the process started.
As Alan said you could always do some testing and try to fix it yourself but that can void the warranty and be a very deep rabbit hole!!

PS: What exactly were you doing with the PyTrack? And which MC were you using?
I’ve just picked up a LoPy and have a project in mind but am still wrapping up some in-progress ones :smiley:

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7

Hi Liam,

I did have a look at all the connections closely and I can’t see anything obvious or no lose components.

I’m using a gpy at the moment, looking to get gps location and sensor data and send it over LTE CAT 1.

I’m reasonably impressed with the pycom stuff so far, super fast to get up and running but the sample libraries and code is a bit dodgy.

Patrick

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8

Hey Patrick,

Unless you’re in a blackspot, it seems quite unusual the GPS receiver is picking up no sats, they’re generally quite relaible so it may be that this particular board is faulty

Earlier on, you said that you have tested some other versions of the GPS library. Do you have any links to the repos that you used? I’ll leave a message for the support team to let them know to grab one here and run your the scripts to see whether we can get the same outcome. :grinning_face_with_smiling_eyes:

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I am pretty familiar with NMEA messages, I decode them for a GPSDO project I’m working on. Unless there is a software way of blocking the antenna from the GPS, I don’t think any amount of software fiddling is going to fix your problem. What those messages clearly say is: no signal. That’s hardware. I’ve used a few GPS modules, even the cheapest pick up a satellite within a minute of being placed outside. They show up in the $GxGSV message.

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10

The biggest impact on time to first fix is the initialization of the device. If it has recorded an approximate position and date then time to first fix can be under a minute. If it has no information about location or time it can take a lot longer. I have seen devices which did not know the epoch take more than 24 hours to get their first fix. I don’t know that item in detail, but does the manufacturer have a utility where you can query the device to get information about its started data, and update for the local approximate position and time? Something like this: m-center | u-blox

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Hi Jeff105671. I wasn’t saying the GPS gets a fix in a minute. Depending on the model, it can take quite a while. If there’s any satellite in view it gets picked up fairly quickly (and shows up in the $GxGSV message). After that, as you say, it can take a while to get a fix. Although 24 hours seems excessive - the almanac data repeats every 12.5 minutes and the GPS may have to wait for that to come around. The only times I’ve seen it take longer is when the signal is really bad. I use VisualGPS program to view the NMEA messages in an easy to read format. But of course there needs to be some form of reception for it to show anything.

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That example is showing no satellites detected. Are there other logs indicating it detected a satellite? I am not sure at what point GSV starts reporting the satellite - whether almanac data is sufficient, or it needs to have the almanac plus an identified satellite. Is that time correct (as UTC)? If so that indicates it found some almanac data. 24 hours is genuine, but I have only seen it happen when the receiver had the wrong epoch - it takes a long time to work out why none of the almanac data adds up. Considering that the last epoch change was April 2019 it is possible that your device is still one epoch out… Did you find a configuration utility at the manufacturer’s site?

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13

Hi everyone,

Thanks for all the replies, finally got to the bottom of this.

I noticed yesterday that my pytrack board didn’t have a jumper on it which is required when using an external antenna. I thought below was some form of mini jumper but then I realised that no it’s just there to maintain the spacing between the pins and for some reason it had come away from the pcb.

pytrack
pytrack2408×1124 477 KB

I connected a jumper and left the board outside and it got a gps fix after about 2 hours, yay! I takes about 2-3 mins to get a subsequent fix from cold start but definitely seems to be working.

Faulty operator not faulty board.

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