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Re: [gpsd-users] ppsthread.c broken for FreeBSD gpio

From: Gary E. Miller
Subject: Re: [gpsd-users] ppsthread.c broken for FreeBSD gpio
Date: Tue, 14 Mar 2017 12:33:20 -0700

Yo Tony!

On Mon, 13 Mar 2017 17:01:12 -0700
"Tony Hain" <address@hidden> wrote:

> > I have a trusty MR-350p,  That is clearly not the default setting
> > for that model. Why do you have it set that way?  it will most
> > likely fall into a deadband that is rejected as hard to quantify.  
> The2.8v pulse coming out of it was inadequate to drive the rs232 on
> the 386's, so I stuck a driver in.

A common mistake, and the standard solution.

> That didn't do anything useful
> because the 2us pulse was too short to be seen by the ntp pps driver,

I have no trouble detecting 1 microSec pulses.  I'd look again at
your motherboard.

> so I put a 555 in.

Also a common solution.  Then set it to 100 micro Sec and you are done.

> At the time (~10 years ago when the oncore died) I
> didn't know about the gpsd edge detector, so I shot for 50% duty
> cycle

Bad idea.  There are 0.5 HZ GPS that output one edge each second.

You can not remove that from gpsd, you will break too many existing

So, at this point, game over, fix your pulse width.

> > Rally?  Where?ode snips please.  
>                 /* brain damaged pps-gpio sometimes never fills in
> clear *prev_clock_ts = pi.assert_timestamp;
>                 *prev_clock_ts = pi.clear_timestamp;
>         *clock_ts = pi.assert_timestamp;

That has been vetted by a ton of people, don't touch that.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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