[time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

STR . strykar at hotmail.com
Mon Aug 15 09:35:46 UTC 2016


Pardon my ignorance, I'm not sure what COM port the PPS is tied to or what you mean.

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Chris Albertson
Sent: Monday, August 15, 2016 2:30 AM
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

Why not use the same COM port the PPS is tied to.  Apparently in can accept the 3 volt serial signal.  The PPS goes to one of the control lines to create an interrupt and the data goes to Rx and Tx.

On Sun, Aug 14, 2016 at 9:37 AM, STR . <strykar at hotmail.com> wrote:

> Thanks for your previous email, it shed light on the situation of 
> choosing COM ports.
>
> COM1 is required for console access so that's out.
> COM2 has headers and seemed like an obvious choice as I have no real 
> need for a 2nd serial port.
>
> I wish to power the GPS via the mini-PCI slot to avoid soldering power 
> cables along with a PPS line.
> Will there be any difference in jitter between using the COM2 header 
> or
> COM3 provided by the NCT5104D GPIO pins?
> Or will they both be identical in performance?
>
>
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of 
> Attila Kinali
> Sent: Sunday, August 14, 2016 5:30 PM
> To: Discussion of precise time and frequency measurement < 
> time-nuts at febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to 
> APU2 SoC serial port for ntpd
>
> On Sun, 14 Aug 2016 08:29:48 +0000
> "STR ." <strykar at hotmail.com> wrote:
>
> > Serial port 3 and 4 are provided via the GPIO pins connected to an
> NCT5104D I/O controller which is 5V tolerant.
> > http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pd
> > f I believe that's why it was suggested to avoid the 3V-5V 
> > conversion.
>
> Oops.. I missed that the other UARTs were connected to the GPIO header.
>
> If you use those, you can directly connect the LEA outputs, as the LEA 
> does use 3.3V CMOS for I/O.
>
>                         Attila Kinali
> --
> Malek's Law:
>         Any simple idea will be worded in the most complicated way.
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-- 

Chris Albertson
Redondo Beach, California
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