`Am Freitag, den 13.03.2015, 08:50 +0100 schrieb Uwe Kleine-König:> On Thu, Mar 12, 2015 at 09:57:53AM +0100, Philipp Zabel wrote:> > Am Mittwoch, den 11.03.2015, 18:21 -0700 schrieb Stephen Boyd:> > [...]> > > Why does Philipp like 110Hz the most? Where is the desire for that rate> > > coming from?> > > > > > > And the lower> > > > abs(1 / 110 - 1 / r) the better. > > > > > > Similarly, where is this requirement coming from? Some datasheet? Or is> > > it just some arbitrary decision we've made that may not hold true for> > > all consumers?> It's not comming from a datasheet. But that's what I guess is the right> metric for quite some cases. E.g. an UART sample rate and I also> wouldn't be surprised if Philipp's panel example would call for this> metric, too.> > For an UART running with say 38400 Bd you want to sample with a freqency> of 38400 Hz (not considering oversampling, but that is only a factor> that doesn't makes my reasoning wrong). If you now consider 38401 Hz and> 38399 Hz the respective deltas are 1 Hz. But if you look at the time> between two samples we have:> > 	38401 Hz -> 26.04098852 us -> delta: 0.6781507 ns> 	38400 Hz -> 26.04166667 us> 	38399 Hz -> 26.04234485 us -> delta: 0.6781861 ns> > So with 38401 it takes a little longer until the slightly deviating rate> results in sampling the wrong bit.> > > In this use case, the driver doesn't want the pixel clock to stay below> > a hard frequency limit, but to get as close as possible to the target> > frequency, either above or below, so the relative error to the nominal> > panel refresh rate stays as small as possible. Thus for a fictional> > target rate of 110 Hz, I'd like to minimize abs((round_rate / 110) - 1).> Note that minimizing> > 	abs((round_rate / 110) - 1)> > is equivalent to minimizing> > 	abs(round_rate - 110)Of course, and you're right, I should want to minimize the delta of theinterval time, not of the rate so that if playing back a video stream atexactly the nominal frequency, it takes as long as possible until I haveto drop or duplicate a frame to stay in sync.regardsPhilipp`