[ntp:questions] Re: Looking for time sync hardware supported under Linux for under $400?

Paul.Croome at softwareag.com Paul.Croome at softwareag.com
Wed Jan 18 07:33:08 UTC 2006


The chip you want is RS232 (needs a single +5V power supply), or RS3232
(needs a single +3V power supply).

Look here for the datasheets:
http://www.maxim-ic.com/

Paul
--------------------------------------

Richard B. Gilbert schrieb:

> Mark Hansen wrote:
>
> > On 01/17/2006 12:01 PM, Steve Kostecke wrote:
> >
> >> On 2006-01-17, Mark Hansen <meh at NOSPAMwinfirst.com> wrote:
> >>
> >>> It is possible to find a time synchronization device which is
> >>> supported by the NTP software (NTP version 4.2.0.a on CentOS 4.2) for
> >>> under $400?
> >>
> >>
> >> Garmin GPS-18LVC
> >>
> >
> > Thanks. Can I please ask a couple other questions about this?
> >
> > The documentation for it says that the serial interface is TTL levels
> > (which are 0-5v, if I understand correctly), rather than what would be
> > expected by a PC serial port (which are 0-15v, again IIUC).
> >
> > Can this just be connected to the PC serial port, or will I have
> > to build/buy a TTL -> RS-232 converter/adapter?
> >
> > I looked through the 'Comprehensive list of clock drivers' supplied with
> > the NTP software, and didn't see this device mentioned. Is it know by
> > another name to the NTP software?
> >
> > Thanks again!
>
> You will need to shift the levels;  RS232 uses both positive and
> negative voltages for signaling.  I believe that there is a chip that
> will convert TTL to RS232 levels.  I vaguely recall a number like MC1447
> but that's just a vague recollection; get the facts before you spend
> your money!  You will, of course, need both positive and negative supply
> voltages; I think +/- 12VDC will get the job done and you might even get
> away with +/- 5VDC.
> 
> The Garmin  GPS-18LVC uses the NMEA driver.




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