which pmod gps module

[dzhang]

Hi,

The bag my pmod gps came in says features GMS-U1LP, but the sticker on the module reads PA6H0Y1614, which would indicate it is FGPMMOPA6H?  So Which GPS receiver module do I have?  I ordered this recently if that helps.

Thanks

Donald

[jpeyron]

Hi Donald,

I am currently working on getting confirmation but i believe that it is the FGPMMOPA6H as per the sticker. I will be able to get you a response tomorrow. Sorry about the inconvience.

cheers,

Jon

[jpeyron]

Hi Donald,

The FGPMMOPA6H is a drop in repacement for the GMS-U1LP. Your PmodGPS has the FGPMMOPA6H. The resource page for the PmodGPS has some microcontroller example code is Here.  Here is the PmodGPS IP if you are using Microblaze or Zynq with FPGA's. Here is the reference manual which has a specific pdf reference manual for the FGPMMOPA6H. Hope this helps!

cheers,

Jon 

[dzhang]

Thanks Jon.  A followup question I have is do you know where I can find a document that details all the NMEA messages ($PMTK messages) that I can issue to the GPS?  For my application I am hoping to get sub ms precise timing from the GPS.  In order to do that I think I need the NMEA messages coming out to be synced to the 1pps (by synced I don't mean they have to come out at the same time, just that there need to be a fixed timing relationship between the two).  I have put both signals on the scope and saw the NMEA messages wander around relative to the 1pps, which is not useful if I need to obtain precise timing from the UTC messages and the 1PPS.  

Thanks

Donald

[D@n]

@dzhang,

You might be able to find the NMEA message structure online, but the last I checked the official standard was not open, but rather for sale.

The $PMTK messages as I understand, though, are not a part of the NMEA standard but they are specific to a certain vendor.  I will admit, though, it's been a while since I've googled these so I might be wrong.

But ... let's go on to that sub-ms timing from GPS.  I think you will struggle to get the NMEA messages so timed.  The way the protocol works, the GPS chipset sends the NMEA messages roughly between the second boundaries.  As a result, you're likely to find a couple hundred milliseconds before and after the NMEA messages come from the chip.

If what you are looking for is sub-ms timing, you really need to be paying attention to the PPS signal.  That signal is supposed to be highly accurate.  I've managed to measure it's synchronization with my own clock at less than 100ns, so ... this is doable.  (I've even posted that project online ...)  Getting the NMEA messages to that accuracy ... is likely to be a problem.

Just some thoughts,

Dan