I wonder if the following scheme would work to improve measurement precision over USB for use with GPS devices or similar.
Instead of USB interrupt transfers, which occur on 1 ms boundaries with some unknown epoch, use bulk transfers. In the good case, there are no other USB transactions in flight, the request goes out immediately, the device responds immediately, and the entire link has the lowest latency possible. If these conditions don't hold, the completion time will be delayed. Now use robust estimation techniques to get rid of these exceptions and instead follow the smooth line of best-case responses. NTP implementations do something like this already, but at longer timescales, and targeted at Internet links rather than a single local USB link. If the best-case response time is calibrated out, how good can this get? Microseconds? Cheers, Peter _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
