[time-nuts] Re: Network interface cards that support timestamping

[S McGrath]

Most common way of getting 1PPS into a computer without a dedicated 1PPS
interface is to drive a RS-232 port’s Carrier Detect pin (pin 1 on DB-9)
with the 1PPS signal

On Mon, Jan 30, 2023 at 3:19 PM John Miller via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hey All,
> I'm curious as to what the collective experience is amongst this group
> when it comes to feeding a timestamp signal into a NIC, either for PTP
> purposes or for as a normal PPS refclock. The Intel i210 PCIe network card
> has a few software defined pins that can be used for this purpose, and the
> chrony documentation has some information about it:
>
>
> https://chrony.tuxfamily.org/examples.html#_server_using_reference_clock_on_nic
>
> I imagine most of us here use traditional RS232 serial ports to get this
> signal into an x86 computer, usually using the DCD pin. I've found some
> implementations of RS232 on PCs don't implement all of the additional
> signaling pins, so sometimes DCD is flat out missing. In other cases -
> especially with smaller embedded-type boards only UARTs with Rx/Tx are
> available to the user. (I'm fiddling with using GPIO pins on a few such
> systems, but it's quite a struggle.) So, there is a need for getting PPS
> signals into systems.
>
> There are also highly specialized network interface cards, such as this
> one: https://www.ebay.com/itm/404117321209
>
> ... which does explicitly support PTP timestamping, but it's not clear to
> me if it could pull in a "standard" PPS signal to be made available to
> chrony or NTPsec. I haven't found much documentation on the NT20E2 yet,
> unfortunately, and it may simply not exist for hobbyists.
>
> Does anyone here know if any other network cards that support software
> defined pins, like the i210 does, or any other methods for getting a PPS
> signal to be fed into a PC, and of course interpreted correctly?
>
> Thanks!
> John
>
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