[time-nuts] Linux PPS clues?

Attila Kinali attila at kinali.ch
Thu Oct 20 05:05:56 EDT 2016

On Thu, 20 Oct 2016 08:15:03 +0000
Ilia Platone <info at iliaplatone.com> wrote:

> Actually the system for timestamping is at design stage yet.
> I expect an event rate of about 100kcps, but I found little infos about 
> the bandwidth variable for the receivers.

100kHz event rate is quite a bit. You will need a relatively fast
processor to handle that. 200MHz would be probably the minimum
with a uC, I guess 400MHz with a linux based system.

> Since I don't want to fill in the list with off-topic posts, just limit 
> in time-related quests.
> There's not any problem for the board I'll use, I referenced the 
> raspberry because it's well known. 

Yes, but in embedded there are huge differences between the various
boards and processors. While an rpi is a great device if you want
to do graphics based stuff, it's a very poor choice for control
and measurment applications, or anything that needs fast I/O

> My questions are for the software 
> side and relative efficiency of the system.

The software side varies with the CPU and the subsystem used.
I don't know what linux offers as facility to use the timer
units. A quick glance at the code didnt reveal anything.
Worst case you would have to write a small driver (probably
100-200 lines of code) for it.

If you want, I can ask some of my friends to see what is available for
this kind of stuff.

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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