Date: Sat, 7 Sep 2019 09:18:59 +0930 From: "O'Connor, Daniel" <darius@dons.net.au> To: Ian Lepore <ian@freebsd.org> Cc: "usb@freebsd.org" <usb@FreeBSD.org>, "freebsd-arm@FreeBSD.org" <freebsd-arm@FreeBSD.org> Subject: Re: Is it a good idea to use a usb-serial adapter for PPS input? Yes, it is. Message-ID: <0A7796DA-508B-4FE6-B5C0-391EC5F46C86@dons.net.au> In-Reply-To: <9D2ACA87-C2DB-40D9-9638-B0E215A4EEC0@dons.net.au> References: <f1d765814f722fb2c99c9870b3cc2607b4eca2d7.camel@freebsd.org> <B9EFA4D4-C1AD-4181-B421-F6BD53434FA5@dons.net.au> <bfd784f6ac9c939dbe6a243336bc3b6eab02d4f5.camel@freebsd.org> <61B1AAF3-40F6-47BC-8F05-7491C13BF288@dons.net.au> <9E142F1A-5E8C-4410-91F5-7C80B3D0A15B@dons.net.au> <9D2ACA87-C2DB-40D9-9638-B0E215A4EEC0@dons.net.au>
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> On 20 Aug 2019, at 11:37, O'Connor, Daniel <darius@dons.net.au> wrote:
>=20
>=20
>=20
>> On 19 Aug 2019, at 17:09, O'Connor, Daniel <darius@dons.net.au> =
wrote:
>> I am going to try this diff but buildkernel is going to take a =
while...
>=20
> Was a lot faster cross building, so I installed it this morning:
> [gps 1:56] ~ >uname -a
> FreeBSD gps 13.0-CURRENT FreeBSD 13.0-CURRENT #1 =
41a4c010326-c262109(master)-dirty: Tue Aug 20 11:04:57 ACST 2019 =
darius@midget.dons.net.au:/usr/obj/arm-src/arm.armv7/sys/GENERIC arm
>=20
> [gps 1:57] ~ >dmesg|grep pps
> am335x_dmtpps0: <AM335x PPS-Capture DMTimer4> mem =
0x48044000-0x480443ff irq 30 on simplebus0
> [gps 1:58] ~ >ll /dev/pps0 /dev/dmtpps
> crw-rw---- 1 root ntpd 0x41 20 Aug 01:09 /dev/dmtpps
> lrwxr-xr-x 1 root wheel 6 20 Aug 01:09 /dev/pps0 -> dmtpps
>=20
> [gps 1:58] ~ >cat /etc/ntp.conf
> server 10.0.2.1 iburst prefer
>=20
> server 127.127.22.0 minpoll 4 maxpoll 4
> fudge 127.127.22.0 refid PPS
>=20
> [gps 1:59] ~ >ntpq -nc pe
> remote refid st t when poll reach delay offset =
jitter
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
> *10.0.2.1 214.52.129.40 3 u 64 64 37 0.349 -0.631 =
0.299
> o127.127.22.0 .PPS. 0 l 13 16 377 0.000 1.000 =
0.106
>=20
> It certainly seems happier with the PPS than it was before.
Reader, it was not happy after a longer wait.
I ended up getting a newer GPS engine (u-Blox NEO-M8T) and connecting =
it, and after a run overnight I get:
remote refid st t when poll reach delay offset =
jitter
=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
+10.0.2.1 214.52.129.40 3 u 35 64 377 0.320 -0.348 =
0.027
-203.31.81.2 27.124.125.251 3 u 53 64 377 12.116 1.311 =
1.951
0.au.pool.ntp.o .POOL. 16 p - 64 0 0.000 0.000 =
0.004
1.au.pool.ntp.o .POOL. 16 p - 64 0 0.000 0.000 =
0.004
2.au.pool.ntp.o .POOL. 16 p - 64 0 0.000 0.000 =
0.004
3.au.pool.ntp.o .POOL. 16 p - 64 0 0.000 0.000 =
0.004
o127.127.20.0 .GPS. 0 l 6 16 377 0.000 0.006 =
0.004
+13.239.113.24 .GPS. 1 u 6 64 377 29.971 -0.054 =
0.074
*103.51.68.133 .PPS. 1 u 56 64 377 45.018 4.821 =
0.143
-103.38.120.36 130.95.179.80 2 u 63 64 377 57.946 -8.622 =
0.242
Which seems quite a lot better :)
Is there a reason to *not* increase the number of time hands in the =
kernel by default?
I suppose it would be good to change it to the same structure as the =
feed forward clock stuff, that way it is much easier to change the =
number of hands at compile time..
--
Daniel O'Connor
"The nice thing about standards is that there
are so many of them to choose from."
-- Andrew Tanenbaum
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