[time-nuts] Generate 1 PPS signal on serial port

Javier Herrero jherrero at hvsistemas.es
Tue Aug 6 11:56:36 EDT 2013


Hello,

On 06.08.2013 17:25, Chris Albertson wrote:
>
> The current Linux kernel has a PPS GENERATOR.   See "pps_gen_parport"
>
> Put WHY would you need this? The documentation for pps_gen_parport suggests
> only using it for crude synchronization of sevel computers but NTP would in
> every case work better for that purpose.
>
> But for whatever reason Linux does PPS in both directions
>
> Be warned that any software PPS gignal will not be great, expect a few
> microseconds or error
>
>
>
>
There are applications for that... I had to do that some time ago, since 
I was required to send a PPS signal aligned to UTC, and a time-stamp of 
this PPS signal using MIL-1553 (surely this is familiar to some people 
in the list). The time was the UTC time at the computer (well, in this 
case an embedded one, ntp sync'd through LAN). Since at that time (not 
that long ago) there was not a pps generator available in the linux 
kernel, I developed a small kernel module to drive an ouput pin. It 
worked nicely enough, with a few microseconds of error - completely 
tolerable in that application.

Regards,

Javier



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