[ntp:hackers] u-blox reference clock driver

[Achim Gratz]

Udo van den Heuvel via devel writes:
> On 19-08-18 18:22, Achim Gratz via devel wrote:
>> The trouble with GPIO is that it's either only
>> available on a few boards that aren't very widespread and PCI(-e) cards
>> (aside from the LTP cards)
>
> So LPT cards would be acceptable, usable?
> If so: are they supported already for what we want to do?

I think most PCI(-e) cards should be OK, they usually come with two
additional RS232 ports at insignificant incremental cost.  I have not
used these for PPS, though.  But they are supported in applications that
are fairly sensitive to timing and use bit-banging as the driver
principle, so it can't be too bad.  You might have to spend some time
with your mobo documentation to find a slot that doesn't share it's IRQ
with something else.

>> hold of a card with a Brooktree video capture chip set and breaking out
>> the GPIO from there (which are fully supported in the Linux kernel).
>
> A video capture card appears as not so `lean` or dedicated solution to
> obtain GPIO lines to me.

These cards are sometimes sold surplus at really silly prices and they
give you 24 GPIO lines if you break all of them out, so if you want GPIO
and nothing else, this is hard to beat.  If you only want one or two
GPIO, then LPT is probably a better way.


Regards,
Achim.
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