|Subject:||Re: [gpsd-users] Support for PPS on 10Hz Devices|
|Date:||Thu, 3 Oct 2013 02:59:37 +0800|
What is the GPS module. I'll try to find documentation for it.
On Mon, 16 Sep 2013 13:01:37 +0800
Andrew Yong <address@hidden> wrote:
> >> Yep, the PPS still comes in at 1Hz, but for some reason GPSD
> >> doesn't pick it up.
> > How do you know it is coming if you can't see it? What RS-232
> > pin is it coming in on? Have you tried high debugging levels in
> > gpsd to see hat gpsd is seeing?
> I ran it at 10 and grepped for PPS|NTP. Nothing of note is output at
> 10Hz. Same module at 1Hz NMEA has PPS detected.
So gpsd is working fine with PPS for you at 1Hz updates, but not at
10Hz updates, all else being equal? And you see gpsd PPS debug output
at 1Hz but none at 10Hz?
Unless you are on a rocket the 10Hz is no better than 1Hz. Any reason
not to just run at 1H.
Can you get an osciloscope on the pin and see what it is doing?
> I have it on a USB FTDI chip’s DCD pin. I see DCD blinking at 1Hz
> using RealTerm on Windows, regardless of 1/5/10Hz NMEA updates.
Have you fed ntpd from gpsd, that will tell you if your PPS is really good.
> Pretty sure it's picking up PPS correctly at 1Hz as my PPS LED and
> GPSD debug output coincide perfectly.
Rising is sort of relative. What it is picking up is the edge after
> > gpsd can handle everything from a pulse so small the UART does not
> > see both edges to a 2HZ square wave where each edge is on the
> > second. 100 milli Sec is good because there is no ambiguity on
> > which edge, but 1 milli Sec to 200 milli Sec would be equally
> > good. Just let it be.
> That's good to know. At 1Hz it picks both edges and always chooses
> the rising edge. So I'm going to say it works as intended.
the long part of the rectangular waveform, then ignoring the edge after
the short part. So any inverters have no affect.
Any NMEA setence that yields the current time is seconds will do. Sometimes
> However it rejects the PPS because of a "no GPS seconds" error. I've
> requested a firmware for the MTK3339 with $GPZDA sentences in case
> that fixes it.
you just eed to let it run a long while (30 mins) to get itself oriented.
Short term yes, long term you will see a lot worse.
> Anyway, I'm getting around 5-10ms jitter at 10Hz, no PPS.
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