If you can, get a high speed scope (>10MHz) and put it on the end of the line and see what voltages are coming out of the line to the serial port. You might find it is only a volt or less which is not enough to drive the latches.
On 2012-08-01, Hahn, Ron <[email protected]> wrote: > Chris, > > Thank you for these helpful advises. I am recalling many years ago there were > such things as line transceivers that converted the signals from TTL-RS232 > and backwards. Do these still exist in the world and have you perhaps these > part numbers? I am thinking this is the only thing left to try. Except > possibly changing the PPS pulse width. Maybe with the Fat PPS board? This > is reminding me of the old days. Printers and Terminals! :) > > R > > From: Chris Albertson [mailto:[email protected]] > Sent: 01 August 2012 16:40 > To: Hahn, Ron > Cc: [email protected] > Subject: Re: NTP + PPS on Atom motherboards > > All Serial ports are spec'd for RS232 voltage levels but many of then will > still work on TTL levels. My guess (I'm guessing because you don't say) is > that you are feeding the serial port a TTL level signal. The Core 2 Duo > might be fine with this but perhaps the Atom board need "real rs232" and you > will have the level convert the TTL. > > I also had a problem like yours and it turned out to be the serial cable. I > was using about 100 feet of the wrong kind of wire because it was already > pulled through the walls and down two floors. I found I needed to use a > balanced rs422 signal to go that far reliably. But I ended up moving the > computer and using a 3 foot cable. BTW I was using an Atom as well and found > that I had to give the serial ports on that board a very clean in-spec RS232 > signal. > > Guessing again, I doubt your ports are "bad" but they might be spec'd for > rs232 while the core 2 boards are over-spec'd. > > > > On Wed, Aug 1, 2012 at 1:46 AM, Hahn, Ron > <[email protected]<mailto:[email protected]>> wrote: > Colleagues, > > I have been working for some time now trying to get four different Asus Atom > motherboards to successfully work as a NTP stratum 1 server. I am using the > FreeBSD 8.3 OS with PPS compilation in the kernel, and the ntp-devel port > (4.2.7p2?? version ntp). Thanks to the David Taylor web site, I am using the > Sure GPS boards to drive these motherboards and also his MRTG script to > monitor these things too. > > What I am seeing is that the time is off by almost 53,000uS on the MRTG graph > and almost 500mS sometimes on the outputs of ntpq -c pe at times. Other > times it is a few uS from PPS. I have been seeing this on three different > boards (D525, D510, and 330 CPU) so this is repeating. I was thinking this > might be the tty port so I have tried both the tty ports and still the same. > > I have used exactly the same recipe on a Core 2 Duo Tyan server and the times > are maximally off by only +4uS/-2uS from PPS. So I am thinking there is > something fundamental wrong with the Atom boards. I have repeated the > experiments with a Pentium 4 server in another location and I am also seeing > excellent timekeeping too. I am thinking that maybe the Atom clock on the > board is too consumer for these uses?? > > Has others experienced these difficulties with Atom motherboards as Stratum 1 > servers? > > Thanks, > > Ron > _______________________________________________ > questions mailing list > [email protected]<mailto:[email protected]> > http://lists.ntp.org/listinfo/questions > > > > -- > > Chris Albertson > Redondo Beach, California _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
