LKM Timemark Driver

[Achim Gratz]

[off-topic:
 Hal, your replies break threading.  Can you please stop
 doing that?]

Hal Murray via devel writes:
> Could somebody please review this discussion.  I'm trying to catch up.  I can 
> follow most of the details, but I'm missing the big picture.

The big picture is getting less noisy measurements that have a lot less
unaccounted for latency in them.

> What GPS device is involved?  Is there a handy board?  What does it actually 
> do?  I'm guessing it time stamps an input pin.  (Some other GPS unit does 
> that.  I forget which one.)

Yes, the beauty of it is that it's done as a hardware timestamp.  The
navSpark also can do timestamping, but you need to process it via an
interrupt.  I'm prestty sure the Furuno GPS also can do timestamping, at
least the timing modules, but I don't know any details of those (I might
get one anyway).

> Does the PPS logic on the Raspberry Pi use a counter to avoid interrupt 
> latency?

No, given that it's an interrupt driven driver that question doesn't
even make sense.


Achim.
-- 
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