On Dec 1, 2016, at 7:44 AM, David J Taylor <[email protected]>
wrote:
Venus838LPX-T. Seems to go into a non-locked state for a proportion of
the time but still emits a PPS signal, which increasingly deviates from
true UTC. That's using a 25 mm square 28 dB active patch antenna, similar
to the antennas on other similarly located GPS receivers. This was
indoors, on the top floor of a two-storey building, with just the power
fed to it, watching the LED flash.
Maybe I was unlucky? I wonder what experience others have?
From: Nick Sayer via time-nuts
Was the LED on the PPS pin or on the FIX pin?
The FIX pin is nothing like the PPS output. Frankly, I’m not 100% sure what
the rules are for it. When things are working properly, it blinks at 0.5 Hz,
but the leading and trailing edges are something like 120-150 msec after the
second. It’s very, very loose. My own interpretation is that the controller
flips the bit when it’s got nothing better to do.
I’ve not witnessed the actual PPS pin being toggled when GPS isn’t
available, but it’s not a failure mode I’ve expended a lot of effort to
examine.
===================================================
Nick,
I had to dig out the module to check, but as far as I can tell the LED is
connected to pin 7 on the chip, listed as GPIO0/LED on the data sheet.
Nominally, navigation status.
The PPS output which I was monitoring comes from the PPS pin (40) on the
chip - GPIO3/P1PPS1
Cheers,
David
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