[time-nuts] Advice on NTP server needed

Chris Albertson albertson.chris at gmail.com
Mon Jun 13 22:37:13 UTC 2011


I think it may be the voltage.  Do the USB converts use rs232 levels
or only 5 volts?

For NTP the issue is different.   The PPS signal coming from the GPS
needs to go into a hardware serial port so the PPS handler sees a very
low but more importantly a predictable latency.    The PPS depends on
a very specif interface to the hardware interrupt controller.

On Mon, Jun 13, 2011 at 3:25 PM, Alan Melia <alan.melia at btinternet.com> wrote:
> This is raising an interesting point, only vaguely relevant, but we have
> been
> testing some software for amateur radio astronomy purposes that controls
> intruments over serial lines RS-232 or RS-485. Whilst many application run
> with out problems for days on internal serial cards, we seem unable to find
> any USB to serial converter that performs anywhere near as well.on our
> loopback tests. Many of the fail rates suggest that slower speeds give a
> longer period between errors, but with one well-known converter we could not
> run at all at 57.6kB. This may not be too much of a problem with GPS control
> program speeds but it would seem there are few totally reliable products. It
> may be much more serious for NTP operations.
>
> Of the USB converters the best seemed to use the FTDI chip and driver, but
> even
> these have shown fails suggesting the problem is deeper inside the PC. All
> problems have been on the PC reception leg, causing corruption, and often
> what seemed like a driver disconnection so the "serial port" became
> disconnected from the application, and required the app restarting.
>
> Alan G3NYK
>
> ----- Original Message -----
> From: "David VanHorn" <D.VanHorn at elec-solutions.com>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Monday, June 13, 2011 10:46 PM
> Subject: Re: [time-nuts] Advice on NTP server needed
>
>
>>
>> ________________________________________
>>
>>
>> Unfortunately, my D525 mobo doesn't have a serial port and my symetricom
>> doesn't like the usb converter. One of these days somebody is going to
>> make a usb coverter that really looks like a serial port. I'm probably
>> going to buy a serial card for the box if all else fails.
>>
>>
>>
>> The best serial port boxes I have found, are Edgeports.  They are
> available in 1/2/4/8/16 port versions, and I've picked up the 8 port
> versions for $50 on ebay.
>> Dead solid, and reliable.  I haven't hit anything that wouldn't work with
> them.
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California



More information about the time-nuts mailing list