PmodGPS and Getting Started

[JohnA.]

Hello,

I have a Diligent PmodGPS hooked up to a ZedBoard and I was wondering if anyone might be able to offer tips, or direct me to documentation on how to get started.  As it is, I am able to receive and parse sentences and fetch the fields--I'm starting out parsing GPRMC sentences, by the way.  Right now, I don't see any content and the data fields such as the "Status" show "V" for "Invalid Data" and "Mode" shows "N" which I believe also suggests the data is not valid.  The LED on the PMod board is blinking, which I believe means it has not received GPS data.

Is there something I may need to do to initialize the GPS device?  I might have missed that in the documentation I've found.  

And, for what it's worth, I have tried both with and without the separate external antenna attachment.

Thanks for your help!

JohnA

[JColvin]

Hi @JohnA.,

It looks like this thread slipped through the cracks; I apologize.

I don't know what resources you happen to have used, but did you follow the Getting Started with Digilent Pmod IPs tutorial that we have? Additionally, what version of Vivado are you using and if you happen to be using the Digilent IP core, did you use the default application project?

And I guess as an additional check, does your environment offer clear access to the outdoors? The office I am located in is a metal building which offers it's own challenges for GPS which is why I ask.

Thanks,
JColvin

[JohnA.]

Hi JColvin,

The "metal building" thing may be my issue.  So far, I have only tried moving closer to a window.  Maybe outside is the next step.

For our purposes, we did not start with the default application project.  We have the PMODGPS interfacing directly to logic in the FPGA Fabric, rather than directly to the Zynq in the Processor Space.  Is there anything that the Digilent model does to initialize the GPSPMOD, or should we be able to connect to it and just start receiving valid data once a satellite connection has been acquired?  We definitely have not sent any configuration sentences to the PMODGPS at all--so far, we are only receiving.

We are definitely receiving GPS sentences; but the data valid indicator suggests there is no valid data and the mode indicator appears to suggest no defined mode.  I've attached a document with a capture of a few sentences and what we are interpreting their content to mean.

Thanks!

JAkin

GPS_Sentence_Capture.docx

[JColvin]

Hi @JohnA.,

I was receiving the same message of no satellites in view, so I will attempt this today in a different location besides my office window, though I will likely use a different board with a Zynq 7020 chip so I don't have to worry about the 12V power supply that's needed for the Zedboard, though the sentences you are receiving seem to be interpreted accurately

(some time passes)

Yes, you will likely need to step outside. I went outside to the parking lot with a smaller Zynq board that could be powered from a laptops USB port and the GPS was successfully able to find 3 satellites and start reporting latitude and longitude data within about 15 seconds (the data sheet for the GPS module, https://reference.digilentinc.com/_media/reference/pmod/pmodgps/globaltop-fgpmmopa6h-datasheet-v0a.pdf, says a cold start can take up to 35 seconds). I walked back to the office building while the application was still successfully running and the findable satellites dropped to zero pretty much as soon as I reached the front door. You might not have to get all the way outside though, the office building I'm in has an outer sheet metal covering.

Let me know how it goes.

Thanks,
JColvin