Hi everyone, On Fri, Feb 15, 2013 at 1:06 AM, unruh <un...@invalid.ca> wrote: > To get an estimate you could output a pulse on one of RPi's GPIO pins as > soon as it gets the PPS and begins to process the input, and then compare them > on a high bandwidth digital scope. Certainly I would not be surprized at > 1usec, but 10 would be surprizing. > I did this on a router using a custom GPIO PPS driver which asserts another GPIO port after receiving the PPS edge, the PPS echo returned after 0.5 us. This is a polling driver, interrupt driven GPIOs would probably have a higher latency.
On Fri, Feb 15, 2013 at 1:03 AM, unruh <un...@invalid.ca> wrote: > The evidence from the people who do radio astronomy ( who use gps to > provide the time base for long baseline interferometry I believe) is > that it is good to better than that. I cannot point you to the relevant > documents unfortunately. > Now it is true that this depends on the receiver, and I recall tests > that the more recent Motorola timing receivers at the time had an > unexplained 30ns difference from the older ones. But that is ns, not us. > Computers are good to us. > Found some resources about VLBI timing and GPS PPS comparisons here: http://www.cnssys.com/publications.php _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions