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

[S McGrath]

Driving Pin1 only works with a ‘real’ serial port on a dedicated IRQ.  a
USB interface will add unpredictable latency

On Mon, Jan 30, 2023 at 6:16 PM Lux, Jim via time-nuts <
time-nuts at lists.febo.com> wrote:

> On 1/30/23 12:28 PM, S McGrath via time-nuts wrote:
> > 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
>
>
>
> back in the day when that tied directly to an interrupt with consistent
> latency, that works pretty well.
>
>
> These days, though, there's often USB hosts in the way, or some other
> intermediate interfaces that increases the uncertainty in timing of
> "when software does something" in response to "external event"
>
>
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