[ntp:questions] Have Pi, have GPS = low powered NTP server?

Ron Frazier (NTP) timekeepingntplist at techstarship.com
Fri Jun 1 12:16:13 UTC 2012



Uwe Klein <uwe at klein-habertwedt.de> wrote:

>Ron Frazier (NTP) wrote:
>
>> Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9
>Mail.
>The dog ate my eMail ;-)

Hi Uwe,

Yup.  This dog is pretty clever.  Best email I've found for Android.  I can even send from different identities, which I have to for message lists.

>
>> (PS - If you email me and don't get a quick response, don't be
>concerned. I get about 300 emails
>> per day from alternate energy mailing lists and such.
>set up filters for sorting your eMail into different folders.
>( I'd shoot myself before sifting through .5k of eMails per day.)
>

Yes, filters are essential.  I am interested in these topics but don't have the time to read them all.  Most dump into folders for future research.  I also set up different TO addresses in my domain name mail server.  So, if I want to receive email at some time from Sony (just pulling a name out of the air to pick on), I could set up ultraspecialsonydata AT MYDOMAIN.com .  If they treat me nice, I'll keep getting the mails.  If they treat me badly, I can dump that address, lose their mail and anyone they've sold the address to, and not lose my other more important mail.  It's somewhat of a hassle to set up but works well.

>> I'm not asking about how to sort the hardware out, I can handle that
>I think. Just the opinion
>> from anyone who knows more about Linux(Debian or??) on the ARM cpu,
>and it's ability in this
>> respect.
>> 
>> It's said, that the RasPi, has about the same cpu "grunt" as a 300MHz
>Pentium, but I have no way
>> to qualify that statement.
>
>If eth goes over USB you introduce significant delay _and_ granularity.
>USB ( whatever speed) is a polled system! ( 1ms slots afair )
>look into how the eth dev is set up.
>Modern ones tend to have "globbed" interrupts. i.e. one int for
>multiple packets.
>Havock for anything that expects expedient package delivery.

When I was testing my USB GPS with NTP, I was getting + / - 10 ms accuracy without PPS.  I found that this NMEA data was not usable however because the start time of the NMEA sentence wanders about 70 ms in either direction.

When I switched to a serial GPS with PPS and fed that through a Trendnet TU-S9 USB Serial adapter which passes handshaking signals, I could get it down to + / - 1ms accuracy.  That's not great, but is plenty good for some purposes and is about the only option for PC's with no serial port, like laptops.

On my desktop machine, which I had to add a motherboard cable to for a real serial port, I get + / - 40 us accuracy.  I like that much better.

Sincerely,

Ron

>
>CPU omphf should never be a problem. ia32 33MHz system  used to run ntp
>well!
>
>uwe
>



--

Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
Please excuse my potential brevity.

(To whom it may concern.  My email address has changed.  Replying to former
messages prior to 03/31/12 with my personal address will go to the wrong
address.  Please send all personal correspondence to the new address.)

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and such.
I don't always see new email messages very quickly.  If you need a reply and
haven't heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT techstarship.com


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