On Tue, 23 Oct 2007, Marcell Missura wrote: > Hello Brian,
http://cygwin.com/acronyms/#PPIOSPE I've redirected this message and set the Reply-To appropriately. > I'm a student at Bonn university and I'm researching robotics. I'm trying > to write a robot controller for Windows XP (wasn't my choice!) and > measuring elapsed time down to milliseconds precision is crucial. Do you > happen to remember this discussion on the cygwin mailing list? > > On Mon, 12 Feb 2007, Carlo Florendo wrote: > > <snip> > > Re: strange bug in gettimeofday function > > > Windows could be accurate up to 15 ms or perhaps a little bit more. > > However, it is very difficult to achieve less than 15 ms or microsecond > > accuracy with windows due to the limitation on the OS itself. Our > > extensive tests on windows clocks and timers reveal that windows cannot > > be accurate to the microsecond level or below 15 ms. > > > > In any case, in my experience, windows cannot be accurate with a > > precision of up to 15 milliseconds. > > I'm sorry, could you repeat that value one more time, just in case someone > missed it ;-). > > Anyway, I don't think it is relevant to the original thread's question, > but I can assure you that Windows can be used for accurate timings in down > to 1 or 2 ms (depending on the OS version). > > </snip> > > I'm experiencing pretty much the same thing as this guy. I'm using > gettimeofday() to construct a timestamp and ran a test just like this: > Maybe try the solution I gave "this guy" (Carlo Florendo) on the cygwin list? > double timestamp; > struct timeval tv; > > while(1) > { > gettimeofday(&tv, NULL); > timestamp = tv.tv_sec + (double)tv.tv_usec/1000000; > printf("%f\n", timestamp); > } > > Output: > > 1193149915.220881 > ... many times ... > 1193149915.220881 > 1193149915.230881 > ... many times ... > 1193149915.240881 > > and so on. The timestamp changes every 10 ms. > > So if you know how to measure 1ms (less would be even better) on Win XP, > can you please tell me how to do that? http://cygwin.com/ml/cygwin/2007-02/msg00740.html -- Brian Ford Lead Realtime Software Engineer VITAL - Visual Simulation Systems FlightSafety International the best safety device in any aircraft is a well-trained crew... -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
