Hi Ian, Firstly, this is a very cool test - thank you for running it :)
> On 3 Aug 2019, at 06:46, Ian Lepore <i...@freebsd.org> wrote: > PPS(2) is an FTDI 232R, a USB 1.1 serial adapter, connected to a port > on a USB 2.0 hub that's connected to a USB 2.0 host port on the > Wandboard. > > PPS(3) is an FTDI 4232H, a USB 2.0 serial adapter, connected to a port > on the same USB hub as PPS(2). <snip> > Most people are not worried about their kernel clock being 200 > microseconds off from UTC, even if they're using the PPS signal from a > GPS receiver. So I think most people should feel completely at ease > using a USB serial adapter as the input device for a PPS signal. Does the USB clock derive from the 10MHz Rb clock? If so that would mean you would see a lot less jitter than a 'normal' user where the USB clock is not locked too GPS. Do you have a more detailed write up of things like the NTP configuration file? I think I could replicate your test here although I have a Beaglebone Black, not a Wanboard so I will need to check if it can take an external clock. (We have GPS modules & Rb oscillators at work to create reference clock for bi-static meteor applications). Thanks again. -- Daniel O'Connor "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum _______________________________________________ freebsd-usb@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"
