ublox NEO-M8T Pi Hat

Paul Theodoropoulos paul at anastrophe.com
Sun Apr 21 01:07:29 UTC 2019

I managed to fry my previous M8N board that I'd cobbled together some time 
back. Poking around on ebay I ran across a slick little pi-zero 
form-factor HAT  with M8T and onboard replaceable battery. Wired up PPS, 
and have it up and running. Took some poking at the ublox u-center to get 
it spitting out the 'right' nmea info, though no idea if all the strings 
are necessary (most of the thousand or so configs in u-center are far too 
arcane for my understanding).

Initially it was just pumping out long hex strings - not garbage, specific 
hex. Now I have it putting out NMEA - but there's still one string in the 
output in hex, and i'm not really sure what it is or how to fix/hide it, 
or if i even need to bother? - example from gpsmon:

(43) $GNGST,002725.00,2885796,,,,6.7,5.6,14*5D
(38) $GNZDA,002725.00,21,04,2019,00,00*77
(40) $GNGBS,002725.00,6.7,5.6,13.7,,,,,,*6A
(33) $GNVLW,,N,,N,0.000,N,0.000,N*44
------------------------------------- PPS 
(36) $GNDTM,W84,,0.0,N,0.0,E,0.0,W84*71
(70) $GNRMC,002726.00,A,3819.91911,N,12241.32940,W,0.013,,210419,,,A,V*00
(35) $GNVTG,,T,,M,0.013,N,0.025,K,A*38

One "neat" thing is that I'm getting three SHM outputs - SHM(0) GPS, 
SHM(1) PPS, and SHM(2) PPS. The differences between the two are trivial, 
but ntpsec does select the non-preferred one as one of the reference clocks.

The seller doesn't appear to have any more at this time, but I've put up 
some screenshots from the listing as well as the board now as I'm 
finishing up the build.

ebay listing: https://i.imgur.com/sdBlMFW.jpg
Top of board: https://i.imgur.com/UdUbd1R.jpg
Bottom: https://i.imgur.com/WRG9Vth.jpg
Schematic: https://i.imgur.com/4CLsCiQ.png
Ready to deploy: https://i.imgur.com/qJuSn42.jpg

Paul Theodoropoulos

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