Re: [ntp:questions] Atheros AR9331 w/GPS + PPS

[Gabs Ricalde]

On Tue, Sep 1, 2015 at 3:22 AM, Paul J R  wrote:
> Hi All,
>
> Thought I might share my experiences. Got given a little AR9331 based router
> some months ago (gl.inet 6416a) and spun up pps on one of its gpio lines.
> Its been running for about 2 months and so far the performance of it has
> been quite impressive from a client perspective. Havent seen many references
> to anyone using an Atheros chipset for pps and ntp so far but im curious if
> anyone else has had any experiences?
>
> Regards, Paul
>

I've been running two devices (TPLink WR703N, MR3020) for more than 2
years with almost no issue. Also impressed on what these devices could
do. Does the new OpenWRT versions have the PPS driver for AR9331? I had
to use this for Attitude Adjustment:
https://code.google.com/p/openwrt-stratum1/

The GL.iNet looks like it's made for hacking, wish it's sold locally.
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Re: [ntp:questions] Atheros AR9331 w/GPS + PPS

[Gabs Ricalde]

On Tue, Sep 8, 2015 at 5:17 PM, Joachim Fabini
 wrote:
> On 08.09.2015 09:44, Gabs Ricalde wrote:
>> I've been running two devices (TPLink WR703N, MR3020) for more than 2
>> years with almost no issue. Also impressed on what these devices could
>> do. Does the new OpenWRT versions have the PPS driver for AR9331? I had
>> to use this for Attitude Adjustment:
>> https://code.google.com/p/openwrt-stratum1/
>
> Thanks for the pointer, nice project. However, one side-note: the y-axis
> label in the diagram shown on the google code page can't be correct -
> the unit must be ms, NOT µs.
>
> An offset smaller than +-200ns is imho ways out of reach for such
> devices, 200µs is feasible. In particular when considering the
> mechanisms used according to the PpsGpioPollDriver description (100µs
> interval waiting/polling). Still the accuracy is good and should be
> sufficient for many tasks.

The scale is correct, if I run ppstest I get this:

root@OpenWrt:~# ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1441711928.9, sequence: 6248816 - clear
0.0, sequence: 0
source 0 - assert 1441711929.99949, sequence: 6248817 - clear
0.0, sequence: 0
source 0 - assert 1441711931.4, sequence: 6248818 - clear
0.0, sequence: 0
source 0 - assert 1441711931.99970, sequence: 6248819 - clear
0.0, sequence: 0
source 0 - assert 1441711932.99929, sequence: 6248820 - clear
0.0, sequence: 0
source 0 - assert 1441711933.99983, sequence: 6248821 - clear
0.0, sequence: 0
source 0 - assert 1441711934.99966, sequence: 6248822 - clear
0.0, sequence: 0
source 0 - assert 1441711936.1, sequence: 6248823 - clear
0.0, sequence: 0
source 0 - assert 1441711936.99960, sequence: 6248824 - clear
0.0, sequence: 0
source 0 - assert 1441711937.99962, sequence: 6248825 - clear
0.0, sequence: 0

The 100 us interval is only for determining the coarse time.

> Joachim
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Re: [ntp:questions] Atheros AR9331 w/GPS + PPS

[Joachim Fabini]

On 08.09.2015 09:44, Gabs Ricalde wrote:
> I've been running two devices (TPLink WR703N, MR3020) for more than 2
> years with almost no issue. Also impressed on what these devices could
> do. Does the new OpenWRT versions have the PPS driver for AR9331? I had
> to use this for Attitude Adjustment:
> https://code.google.com/p/openwrt-stratum1/

Thanks for the pointer, nice project. However, one side-note: the y-axis
label in the diagram shown on the google code page can't be correct -
the unit must be ms, NOT µs.

An offset smaller than +-200ns is imho ways out of reach for such
devices, 200µs is feasible. In particular when considering the
mechanisms used according to the PpsGpioPollDriver description (100µs
interval waiting/polling). Still the accuracy is good and should be
sufficient for many tasks.

Joachim
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Re: [ntp:questions] Atheros AR9331 w/GPS + PPS

[Paul J R]

On 8/09/2015 5:44 pm, Gabs Ricalde wrote:

On Tue, Sep 1, 2015 at 3:22 AM, Paul J R  wrote:

Hi All,

Thought I might share my experiences. Got given a little AR9331 based router
some months ago (gl.inet 6416a) and spun up pps on one of its gpio lines.
Its been running for about 2 months and so far the performance of it has
been quite impressive from a client perspective. Havent seen many references
to anyone using an Atheros chipset for pps and ntp so far but im curious if
anyone else has had any experiences?

Regards, Paul


I've been running two devices (TPLink WR703N, MR3020) for more than 2
years with almost no issue. Also impressed on what these devices could
do. Does the new OpenWRT versions have the PPS driver for AR9331? I had
to use this for Attitude Adjustment:
https://code.google.com/p/openwrt-stratum1/

The GL.iNet looks like it's made for hacking, wish it's sold locally.

Yeah, i did stumble onto the code on the google, but i ended up writing 
a new driver myself as that one was polling based.


There was a patch 
(https://github.com/GBert/openwrt-misc/tree/master/gpio-test/src) which 
adds interrupt based gpio support, so i wrote a patch to add pps-gpio on 
top of that 
(https://dl.dropboxusercontent.com/u/49959760/970-pps-gpio-ar9331.patch). Its 
an openwrt patch specifically for the gl.inet board, but the code is 
pretty straight forward (though a bit messy) and should work on any 
ar9331 based box. It'll work on 14.07 and above (though i've only tested 
compiling it against 14.07 and the current trunk code)


I've also tested it with a som9331 openembed board and it seems to work 
quite well on that as well.


Not sure what locally would be for you, but if your in the US, there is 
a 1-day shipping option (i believe) for that particular box on amazon.


To give an idea on size though (which is perhaps what impressed me 
most), here it is next to an RPI2 
https://dl.dropboxusercontent.com/u/49959760/IMG_20150904_014715_w.jpg 
and im very tempted to make a little waterproof box for it, a poe 
splitter and stick it to the roof somewhere as the components i've 
looked at in it all have fairly extreme environment ratings.


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