[time-nuts] Linux PPS clues?

Attila Kinali attila at kinali.ch
Thu Oct 20 03:16:01 EDT 2016

On Thu, 20 Oct 2016 06:15:39 +0000
Ilia Platone <info at iliaplatone.com> wrote:

> I need some clues on the Linux PPS subsystem.
> I am trying to take some timestamps of events on a GPIO using an ARM 
> SBC, and noticed that the kernel linux can be interfaced to a PPS 
> signal, wanted to sync another GPIO to a GPS receiver for time 
> reference. I need to know how much precise this system can be. How much 
> resolution can I obtain with a cheap receiver (maximum quantization 
> frequency)?

Using GPIO for precision timing is the wrong approach. If you are
already using an ARM processor, it is much better to use the time/capture
unit to time events. These are counters which run usually with 50-200MHz
giving you a resolution of 5ns to 20ns. Their advantage is that you are
not limited by the interrupt latency and (mis)behaviour of the software,
but handle everything in hardware.

				Attila Kinali

Malek's Law:
        Any simple idea will be worded in the most complicated way.

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