[time-nuts] NEO-M8N vs. NEO-M8T

Gary E. Miller gem at rellim.com
Mon May 21 14:19:47 EDT 2018


Yo Scott!

On Mon, 21 May 2018 13:08:06 -0500
Scott Newell <newell+timenuts at n5tnl.com> wrote:

> >The NEO-M8T is an FTS product.  
> 
> Are you sure about that? I thought the M8T was timing, and the M8F 
> was FTS. Please check your firmware version string against the table
> on page 8.

I stand corrected.  I do see UBX-TIM-TP:

Class: TIM(0xd) ID: TP(0x1), len: 0x10
tow:1519310.000000000 qErr:-0.000000048400 ps, week:2002
  flags:0xa refInfo:0x0
      is GPS, UTC available

Which says the next PPS is going to be -48.4 nano seconds out.  Similar
to the 52 nano seconds quantization error of a RasPi 3B.

Here is another one, -101 nano seconds out:

Class: TIM(0xd) ID: TP(0x1), len: 0x10
 tow:1522360.000000000 qErr:-0.000000101900 ps, week:2002
   flags:0xa refInfo:0x0 
      is GPS, UTC available

That is more than double my quantizaation error!

Now, how to I tell the Linux kernel to apply that correction?

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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