Daniel O'Connor <dar...@dons.net.au> wrote: > > >> On 17 Jun 2022, at 00:07, David Taylor >> <david-tay...@blueyonder.co.uk.invalid> wrote: >> >> On 16/06/2022 10:00, Thiebaud HUMBERT wrote: >>> To do the inversion, I just changed the "Pulse Mode" parameter to "Falling >>> edge" from "Rising edge". >>> The offset induced by the "pulse length" has disappeared. >>> But there is still an offset of around 10.3ms, which I think is induced by >>> USB as explained in this article about other chipsets >>> (https://lists.freebsd.org/pipermail/freebsd-usb/2019- August/016078.html) >> >> Yes, Thiebaud, USB is not good enough for PPS signals! > > This is absolutely false. > > If you are using it for NTP then GPS+PPS over USB is quite adequate (from > personal experience).
As USB is a two wire interface, there is no such thing as PPS over USB. You of course can get the ASCII data over USB, but to get a PPS signal you in general have to hack a USB GPS and add a signal wire for PPS then hack some interface on the computer to accept PPS. If all you need is accuracy in the 2 millisecond range, most recent USB GNSS dongles will achieve that without PPS. -- This is questions@lists.ntp.org Subscribe: questions+subscr...@lists.ntp.org Unsubscribe: questions+unsubscr...@lists.ntp.org
