[time-nuts] Network interface cards that support timestamping

[John Miller]

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